T.O. 33B-1-2 TECHNICAL MANUAL
NONDESTRUCTIVE INSPECTION GENERAL PROCEDURES AND PROCESS CONTROLS (ATOS) DISTRIBUTION STATEMENT C: Distribution authorized to U.S. Government agencies and their contractors, Administrative or Operational Use, 31 August 1986. Refer other requests for this document to AFRL/MLS-OL, Tinker AFB, Oklahoma 73145-3317. WARNING: This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C. 2751 et seq.) or the Export Administration Act of 1979, as amended, Title 50, U.S.C., App. 2401, et seq. Violation of these export-control laws is subject to severe criminal penalties. Dissemination of this document is controlled under DoD Directive 5230.25. HANDLING AND DESTRUCTION NOTICE: Destroy by any method that will prevent disclosure of contents or reconstruction of the document.
Published under the authority of the Secretary of the Air Force
1 JUNE 2006
T.O. 33B-1-2 INSERT LATEST CHANGED PAGES. DESTROY SUPERSEDED PAGES.
LIST OF EFFECTIVE PAGES NOTE: The portion of the text affected by the changes is indicated by a vertical line in the outer margins of the page. Changes to illustrations are indicated by miniature pointing hands. Changes to wiring diagrams are indicated by shaded areas.
Dates of issue for original and changed pages are: Original . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . . . . . . 1 June 2006
TOTAL NUMBER OF PAGES IN THIS MANUAL IS 138, CONSISTING OF THE FOLLOWING:
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USAF
T.O. 33B-1-2
TABLE OF CONTENTS Chapter
1
Page
INTRODUCTION......................................................vii
2.2.1
SAFETY SUMMARY................................................ix
2.2.2
NONDESTRUCTIVE INSPECTION METHODS, GENERAL INFORMATION.....................................................................1-1 SECTION I INTRODUCTION..............................1-1
2.2.3 2.2.4 2.2.5 2.2.6 2.2.7
Introduction.................................................1-1 Purpose........................................................1-1 Scope...........................................................1-1 Format of Procedures .................................1-1 Knowledge of NDI .....................................1-1 NDI Points-of-Contact................................1-1
2.2.8
SECTION II PROCESS CONTROLS...................1-3
2.3.2 2.3.3
1.1 1.1.1 1.1.2 1.1.3 1.1.4 1.1.5
1.2 1.2.1 1.2.2 2
Chapter
Process Controls .........................................1-3 Reason for Controlling the Process .........................................................1-3 Scope of Process Control ...........................1-3
FLUORESCENT LIQUID PENETRANT INSPECTION.......................................................2-1
2.3 2.3.1
2.3.4 2.4 2.5 2.6 2.6.1 2.7
SECTION I FLUORESCENT LIQUID PENETRANT INSPECTION GENERAL PROCEDURE................................................2-1
2.8
2.1
Fluorescent Liquid Penetrant Inspection General Procedure...................2-1 Preparation of Part......................................2-1 Penetrant Application Procedure................2-2 Penetrant Removal Procedure ....................2-3 Developer Application and Drying Procedure ...............................................2-4 Fluorescent Penetrant Interpretation .........................................................2-6 Bleed-Back Method....................................2-7 Post Cleaning..............................................2-7
2.8.1
SECTION II FLUORESCENT LIQUID PENETRANT INSPECTION PROCESS CONTROL ................................................2-8
2.9.5
2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 2.1.7
2.2
System Performance Test Procedure - Cracked-Chrome Panels ............2-8
2.9 2.9.1 2.9.2 2.9.3 2.9.4
2.10
Page Equipment and Materials Required for Cracked-Chrome Panel Test...............................................2-8 Procedure for Cracked-Chrome Panel Test...............................................2-8 Testing for Failed Penetrant.......................2-9 Testing for Failed Emulsifier/Remover .....................................................2-9 Testing for Failed Developer .....................2-9 Lipophilic Penetrant Systems.....................2-9 Water Washable Penetrant Systems ........................................................2-9 Solvent Removable Penetrant Systems ........................................................2-9 System Performance Test with the PSM Starburst Panel (Depot Only) ......................................................2-9 Procedure for Performing the PSM Starburst Panel Test....................2-10 Response of PSM Panels .........................2-10 Reading PSM Starburst Indications ......................................................2-10 Cleaning PSM Panels ...............................2-11 Inspection Booth Checks..........................2-11 Surface Wetting Test................................2-11 Penetrant Brightness Test - (DEPOT ONLY) ........................................2-11 Penetrant Rapid Brightness Test (FIELD LABS) ....................................2-12 Testing Concentration of Water Based (Method ‘‘A’’) Penetrants.....................................................2-12 Testing Lipophilic Emulsifier (Method ‘‘B’’) .....................................2-12 Lipophilic Emulsifier Removability Test ..................................................2-13 Hydrophilic Remover Refractometer Test .................................................2-13 Hydrophilic Remover Hydrometer Test.......................................................2-14 Hydrophilic Remover Quick Test for Penetrant Contamination................2-14 Hydrophilic Remover Performance Check...........................................2-14 Hydrophilic Remover Background Fluorescence Check .............................2-14 Hydrophilic Remover Spray Solution Test ...............................................2-15 Water-Suspended Developer Concentration Test......................................2-15
i
T.O. 33B-1-2 2.10.1 2.10.2 2.10.3 2.10.4 2.11 2.12 3
Water-Suspended (or Soluble) Developer Coating Uniformity Test.......................................................2-16 Water-Suspended (or Soluble) Developer Penetrant Contamination Test ...............................................2-16 Water-Soluble Developer Concentration Test ...........................................2-16 Dry Developer Contamination Test.......................................................2-16 Cleaning Procedure for Process Control Test Panels..............................2-17 Water Pressure and Temperature Check ...................................................2-17
4
EDDY CURRENT INSPECTION ...........................4-1
4.1 4.1.1 4.1.2 4.1.3
4.2
3.1
4.2.1
3.1.2 3.1.3 3.1.4 3.1.5 3.1.6 3.1.7 3.1.8 3.1.9 3.1.10
SECTION II FLUORESCENT MAGNETIC PARTICLE PROCESS CONTROL PROCEDURES ......................................3-14 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8
System Effectiveness Check (Ketos Ring).........................................3-14 Quantitative Quality Indicators (QQI) ....................................................3-15 Cracked Parts............................................3-16 Amperage Indicator Check.......................3-16 Quick Break Test......................................3-16 Dead Weight Check .................................3-17 UV-A Black Light Intensity and Ambient Light Requirements ..............3-17 Fluorescent Background Check for New Bulk Suspension....................3-18 Particle Concentration Test ......................3-18
Eddy Current General Procedure ...............4-1 Approved Equipment..................................4-1 Eddy Current Scanning Techniques .....................................................4-5 General Eddy Current Inspection Procedures ............................................4-10
SECTION II EDDY CURRENT PROCESS CONTROL PROCEDURES ...................4-56
SECTION I FLUORESCENT MAGNETIC PARTICLE INSPECTION GENERAL PROCEDURE................................................3-1 General Magnetic Particle Procedures .......................................................3-1 Required Equipment and Materials ...........................................................3-1 Preparation of Part......................................3-1 Selecting Type of Magnetizing Current ...................................................3-2 Longitudinal Magnetization (Coil Shots) .....................................................3-2 Longitudinal Magnetism Induced by Portable Yokes..................................3-6 Circular Magnetism Produced by Direct Contact ........................................3-7 Demagnetizing Test Parts.........................3-11 Post-Cleaning Test Parts After Magnetic Particle Inspection ...............3-12 QQI Shims ................................................3-12 Magnetic Particle Inspection Interpretation ...............................................3-12
Vehicle Fluorescence Check ....................3-20 Acidity Test ..............................................3-20 Water Break Test......................................3-20 Field Indicator Check ...............................3-20
SECTION I EDDY CURRENT INSPECTION GENERAL PROCEDURE .......................4-1
FLUORESCENT MAGNETIC PARTICLE INSPECTION.......................................................3-1
3.1.1
ii
3.2.9 3.2.10 3.2.11 3.2.12
4.2.2 4.2.3 5
Eddy Current Process Control Procedures ............................................4-56 General Process Control for Eddy Current Inspection Probes and Standards ..............................................4-56 Probe Test .................................................4-56 Slot Test....................................................4-57
ULTRASONIC INSPECTION .................................5-1 SECTION I ULTRASONIC INSPECTION GENERAL PROCEDURE .......................5-1 SECTION II ULTRASONIC INSPECTION PROCESS CONTROL..............................5-2 5.1 5.1.1 5.1.2 5.1.3 5.1.4 5.1.5 5.1.6 5.1.7 5.1.8
Ultrasonic Inspection Process Control ...................................................5-2 Procedure for Determining Vertical Linearity Limits (ASTM Blocks) ...................................................5-2 Procedure for Determining Horizontal Linearity Limits (Type 2 IIW Block) .............................................5-3 Procedure for Determining Inspection System Sensitivity (ASTM Blocks) ...................................................5-4 Checking Resolution (Type 2 IIW Block).....................................................5-5 A-Scan Straight Beam Distance Calibration..............................................5-8 Angle Beam Distance Calibration (Type 2 IIW Block).............................5-11 Angle Beam Point-of-Incidence (Type 2 IIW Block).............................5-14 Determining Angle Beam Misalignment (Skew Angle)......................5-16
T.O. 33B-1-2 5.1.9 6
Angle Beam Angle Determination (Type 2 IIW Block).............................5-17
RADIOGRAPHIC INSPECTION ............................6-1 SECTION I RADIOGRAPHIC INSPECTION GENERAL PROCEDURE .......................6-1 SECTION II RADIOGRAPHIC INSPECTION GENERAL PROCEDURE .......................6-2
6.1 6.1.1 6.1.2 6.1.3 6.1.4 6.1.5 6.1.6 6.1.7
Radiographic Inspection Process Control ...................................................6-2 Individual Safelight Evaluation Check .....................................................6-2 Collective Safelight Check.........................6-2 Developer Testing.......................................6-2 Fixer Control...............................................6-3 Safelight Filter Check.................................6-3 Interlock Operational Check ......................6-3 Survey Meter Operational Check...............6-3
LIST OF ILLUSTRATIONS Number 3-1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 4-11 4-12
Title
Page
Longitudinal Magnetization in a Coil ............ 3-2 Magnetic Field Produced by a Portable Yoke ........................................................... 3-7 Circular Magnetic Field Produced by Direct Contact ............................................ 3-8 Circular Magnetism Using a CBC ................. 3-9 Circular Magnetism Using a CBC on Ring-Shaped Parts.................................... 3-10 Quantitative Quality Indicators (QQI) ......... 3-12 Ketos Ring .................................................... 3-15 Black Light Intensity .................................... 3-17 Centrifuge Tube ............................................ 3-19 Eddy Current Reference Standard.................. 4-3 Alternate Surface Eddy Current Reference Standard ............................................. 4-5 Required Scanning Directions ........................ 4-7 Scanning Around Fastener with Flush Heads .......................................................... 4-8 Scanning Around Fastener with Protruding Heads ............................................. 4-9 Scanning Radii ................................................ 4-9 Signal Response from 0.020 inch Deep Notch in Aluminum ................................. 4-13 Responses from 0.005, 0.010, and 0.020 inch Deep Notches (Aluminum) with Acceptable Signal-to-Noise ..................... 4-14 Indication Exceeding 10% Vertical Deflection...................................................... 4-15 80% FSH Signal from a 0.020 Inch Deep Notch............................................... 4-18 Impedance Plane Display of 80% Ptp Signal from the 0.020 Inch Deep Notch ........................................................ 4-19 Impedance Plane Response (without High Pass Filter) from the 0.005 Inch Notch (4340 Steel) with Acceptable Signal-To-Noise......................... 4-20
Number 4-13
4-14 4-15 4-16 4-17 4-18 4-19 4-20 4-21 4-22 4-23 4-24 4-25 4-26 4-27 4-28 4-29
Title
Page
Impedance Plane Response (with High Pass Filter) from the 0.005 Inch Notch (4340 Steel) with Acceptable Signal-To-Noise ....................................... 4-21 Typical Lift-off Response with Phase Adjusted Correctly ................................... 4-25 Impedance Plane Display ............................. 4-26 Properly Calibrated Sweep Display ............. 4-26 Acceptable Noise Level from Clean Hole .......................................................... 4-27 30% PTP Signal Requires Evaluation.......... 4-27 Establishing Sync Zero Position of the Nortec Spitfire Scanner............................ 4-29 Establishing Sync Zero Position of the Nortec Minimite Scanner......................... 4-30 Establishing Top, Center Scanner Zero Position (Method B)................................. 4-30 Sweep Display with Alarm Gates ................ 4-31 Impedance Plane Display with Alarm Gates ......................................................... 4-32 Split Screen Display with Sweep Display Alarm Gates and Impedance Plane Display Lift-off Limits .................. 4-33 Example of Crack Indication in Hole with Noise Level Greater than 30%Fsw .................................................... 4-34 Example of Excessive Noise in the Sweep Mode (Left) and in the Impedance Plane Mode (Right) ....................... 4-34 Lift-off Response with Phase Adjusted Correctly ................................................... 4-38 Idealized Response Illustrating Minimum Separation Between Lift-off and EDM Notch Response ...................... 4-39 Properly Calibrated Sweep Display (Steel) ....................................................... 4-40
iii
T.O. 33B-1-2 4-30 4-31 4-32 4-33 4-34 4-35 4-36 4-37 4-38 4-39 4-40 4-41
Acceptable Noise Level from Clean Hole (Steel) .............................................. 4-40 Signal from Hole Subject to Evaluation (Steel) ....................................................... 4-41 SYNC Zero Position of the Nortec Spitfire Scanner (Steel) .................................. 4-43 SYNC Zero Position of the Nortec MiniMite Scanner (Steel)......................... 4-44 SYNC Zero Position (Method B) (Steel) ....................................................... 4-44 Response from 0.030 Inch Interface Notch with Phase at a 45 Degree Angle ........................................................ 4-49 Example of Properly Calibrated Sweep Display (Titanium) ................................... 4-49 Example of Acceptable Noise Level from Clean Hole. Noise Level Shall Not Exceed 10% FSH from Baseline ..... 4-50 Display of Signal from Hole That is Subject to Evaluation (Titanium) ............ 4-50 Establishing SYNC Zero Position of the Nortec Spitfire Scanner (Titanium) ......... 4-52 Establishing SYNC Zero Position of the Nortec MiniMite Scanner (Titanium) ..... 4-53 Establishing SYNC Zero Position of the Nortec Spitfire Scanner (Method C) ....... 4-53
5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 5-13
Use the Type 2 IIW Block to Check Horizontal Linearity ................................... 5-3 Use Type 2 IIW Block to Check Back Surface Resolution ..................................... 5-5 Use a Type 2 IIW Block to Check Entry Surface Resolution ............................... 5-7 Straight Beam Distance Calibration with IIW Block ........................................ 5-10 Straight Beam Distance with Miniature Angle Beam Block................................... 5-11 Angle Beam Distance Calibration with IIW Block................................................. 5-13 Angle Beam Distance Calibration with Miniature Angle Beam Block.................. 5-14 Point of Incidence Determination with IIW Block................................................. 5-15 Point of Incidence Determination with Miniature Angle Beam Block.................. 5-16 Beam Misalignment (Skew Angle) .............. 5-16 Skew Angle Measurement............................ 5-17 Angle Determination with Type 2 IIW Block......................................................... 5-18 Angle Determination with Miniature Angle Beam Block................................... 5-18
LIST OF TABLES Number 1-1 2-1 2-2 2-3 2-4 3-1 3-2 3-3 3-4 3-5 4-1 4-2 4-3 4-4 4-5
iv
Title
Page
Frequency for Process Control ......................... 1-3 Fluorescent Penetrant Advantages and Limitations.................................................... 2-1 Material and Minimum Penetrant Sensitivity Level ................................................... 2-2 Penetrant Dwell Times...................................... 2-3 Developer Dwell Times .................................... 2-5 Fluorescent Magnetic Particle Advantages and Limitations ................................... 3-1 Coil Size vs. Maximum Part Diameter for Bottom of Coil Shot............................... 3-3 Typical Current for Five-Turn Coil with Part at the Bottom of Coil ........................... 3-4 Ring Specimen Indications ............................. 3-15 Empirical Black Light Intensity Requirements at Various Ambient Light Levels for Portable Inspections ................. 3-18 Reference Standard Materials ........................... 4-2 Nortec 2000D Initial Settings for Determining Lift-off Compensation ..................... 4-6 Nortec 2000D Inspection Frequencies by Material......................................................... 4-7 Nortec 2000D Settings for Surface Scan of Aluminum .............................................. 4-11 Nortec 2000D Inspection Frequencies ........... 4-12
Number 4-6 4-7 4-8
4-9 4-10 4-11 4-12 4-13 4-14 4-15 5-1 5-2 5-3 5-4
Title
Page
Settings Prior to Calibration for Surface Scanning of Steel Parts .............................. 4-16 Nortec 2000D Calibration Settings Scanning of Aluminum Fastener Holes ............ 4-23 Frequency Settings Fastener Hole Scanning of Aluminum, Non-Ferrous Alloys, and Weakly Ferromagnetic Alloys.......................................................... 4-24 Filter Settings vs. Hole Diameter ................... 4-24 Sweep Display Alarm Gate Settings .............. 4-31 Impedance Plane Display Alarm Gate Settings ....................................................... 4-31 Settings Prior to Calibration of Nortec 2000D/2000D+ Fastener Hole Scanning of Magnetic Steel Parts ..................... 4-36 Filter Settings vs. Hole Diameter ................... 4-37 Nortec 2000D Initial Calibration Settings for Rotary Scanning of Fastener Holes in Titanium Parts........................................ 4-47 (Titanium) Filter Settings vs. Hole Diameter .............................................................. 4-47 Vertical Linearity .............................................. 5-2 Horizontal Linearity .......................................... 5-3 Minimum Sensitivity Requirements ................. 5-4 Resolution Set-up .............................................. 5-5
T.O. 33B-1-2 5-5 5-6 5-7
Dead Zone Set-up ............................................. 5-7 Limits of Boundary Surface Resolution........... 5-8 Auto Calibration Procedures............................. 5-8
5-8 5-9 5-10
Straight Beam Distance .................................. 5-10 Auto Calibration Procedures........................... 5-12 Angle Beam Distance Calibration .................. 5-13
v/(vi blank)
T.O. 33B-1-2
INTRODUCTION 1.
PURPOSE.
This manual provides information necessary for operating and maintaining the Non Destructive Inspection general procedures and process controls. 2.
IMPROVEMENT REPORTS.
Recommendations for improvements to this technical order will be submitted on AFTO Form 22, Publication Change Request, in accordance with TO 00-5-1. Complete forms will be forwarded to 448 MSUG/GBMUH, Tinker AFB, OK 73145.
vii/(viii Blank)
T.O. 33B-1-2
SAFETY SUMMARY 1.
GENERAL SAFETY INSTRUCTIONS.
The following are general safety precautions and instructions individuals must understand and apply during many phases of operation and maintenance to ensure personal safety, health, and the protection of Air Force property. Portions of this may be repeated elsewhere in this publication for emphasis. Additional safety precautions are contained in AFOSH STD 91-110, AFOSH STD 91-501, and Army: AR 385-10 paragraph 1. 2.
SHALL, SHOULD, MAY, AND WILL.
Use the word ‘‘SHALL’’ whenever a manual expresses a provision that is binding. Use ‘‘SHOULD’’ and ‘‘MAY’’ whenever it is necessary to express non-mandatory provisions. ‘‘WILL’’ may be used to express a declaration purpose. It may be necessary to use ‘‘WILL’’ in cases where simple futurity is required (e.g., ‘‘Power for the meter WILL be supplied by the ship’’). 3.
WARNINGS, CAUTIONS, AND NOTES. WARNING This highlights an essential operating or maintenance procedure, practice, condition statement, etc., which if not strictly observed, could result in injury to, or death of, personnel or long term health hazards. CAUTION This highlights an essential operating or maintenance procedure, practice, condition, statement, etc., which if not strictly observed, could result in damage to, or destruction of, equipment or loss of mission effectiveness.
WARNINGS and CAUTIONS are used in this manual to highlight operating or maintenance procedures, practices, conditions, or statements considered essential to protection of personnel (WARNING) or equipment (CAUTION). WARNINGS and CAUTIONS immediately precede the step or procedure to which they apply. WARNINGS and CAUTIONS consist of four parts: a heading (WARNING, CAUTION, or Icon); a statement of the hazard, minimum precautions, and possible result if disregarded. NOTEs may precede or follow the step or procedure, depending upon the information to be highlighted. The heading used and the definitions are as follows. NOTE This highlights an essential operating or maintenance procedure, condition, or statement. 4.
HAZARDOUS MATERIALS WARNINGS.
Consult the Material Safety Data Sheets (MSDS) (Occupational Safety and Health Administration (OSHA) Form 20 or equivalent) for specific information on hazards, effects, and protective equipment requirements. If you do not have a MSDS for the material involved, contact your supervisor, or the base Safety or Bioenvironmental Engineering Offices. 5.
SAFETY PRECAUTIONS.
The following safety precautions SHALL be observed while performing procedures in this manual. • CAUTION AROUND LIVE CIRCUITS. Operating personnel must observe safety regulations at all times. Do not replace components or make adjustments inside equipment with the electrical supply turned on. Under certain conditions, such as residual charges on capacitors, danger may exist even when the power control is in the off position. To avoid injuries, always disconnect power, discharge and ground circuit before touching it. Adhere to all lockout/tag-out requirements.
ix
T.O. 33B-1-2 • DO NOT SERVICE ALONE. Under no circumstances should any persons perform maintenance on the equipment except in the presence of someone who is capable of rendering aid. • RESUSCITATION. Personnel working with or near high voltage SHALL be familiar with modern methods of resuscitation. Such information may be obtained from the Director of Base Medical Services. • FINGER RINGS AND OTHER JEWELRY. Remove rings, watches, and other metallic objects during all maintenance activity that may cause shock, burn, or other hazards. Snagged finger rings have caused many serious injuries. • PERSONAL PROTECTIVE EQUIPMENT (PPE). The work center supervisor SHALL contact the Base Bioenvironmental Office and/or the Base Safety Office for a list of approved protective clothing/equipment (gloves, apron, eye protection, etc.) for the chemicals, materials, and tools being used. Use nitrile, neoprene, or other protective gloves, aprons, and goggles. The Base Bioenvironmental Office SHALL approve these items in writing. PPE SHALL be worn when and where directed to do so by the Base Bioenvironmental Office. • COMPRESSED AIR. Use of compressed air can create an environment of propelled foreign particles. Excessive air pressures MAY cause injury. NDI Labs typically use compressed air reduced to less than 30-psig and used with effective chip guarding and personal protective equipment (PPE). Lab supervisors SHALL contact the local Wing Safety Office for guidance. • PRECAUTIONS WITH EYEWEAR. Personnel who wear contact lenses shall identify this to their supervisor, refer to the appropriate material safety data sheets (MSDS) for possible hazards involved in wearing contact lenses around chemicals, and abide by the guidance for that chemical. Photochromatic lenses (lenses that darken when exposed to sunlight or ultraviolet light), sunglasses, and colored contacts reduce the visibility of fluorescent indications. This leads to the possibility of faint indications not being seen by the inspector. Therefore, glasses with photochromatic lenses, sunglasses or colored contact lenses SHALL NOT be worn when performing fluorescent penetrant or fluorescent magnetic particle inspections. • SAFETY WITH BLACK LIGHTS. Black light bulbs SHALL NOT be operated without proper filters. Cracked, chipped, or ill-fitting filters SHALL be replaced before using the lamp. Unfiltered ultraviolet radiation can be harmful to the eyes and skin. Prolonged direct exposure of hands to the filtered black light main beam may be harmful. Suitable gloves SHALL be worn when exposing hands to the main beam; UV-A filtering safety glasses, goggles, or face shields SHALL also be worn. A black light bulb heats the external surfaces of the lamp housing. The temperature of some operating black light bulbs reaches 750°F (399°C) or more during operation. The temperature is not high enough to be visually apparent, but it is high enough to cause severe burns with even momentary contact of exposed body surfaces. Extreme care SHALL be exercised to prevent contacting the housing with any part of the body. These temperatures are also above the ignition or flash point of fuel vapors. These vapors WILL burst into flames if they contact the bulb. These black lights SHALL NOT be operated when flammable vapors are present. • SOLVENTS, CHEMICALS, AND OTHER TOXIC MATERIALS. Solvents used may contain aromatic, aliphatic, or halogenated compounds. Many are flammable while others may decompose at elevated temperatures. Solvents SHALL be kept away from heat and open flames. Vapors also may be harmful to personnel, thus adequate ventilation SHALL be used. Contact with skin and eyes SHALL be avoided. Solvents SHALL NOT be ingested. Waste material disposal SHALL be according to applicable directives or as specified by the local Bioenvironmental Engineer/Environmental Management Offices. Keep cleaners/chemicals in approved safety containers and maintain minimum quantities. Some cleaners/chemicals may have an adverse effect on skin, eyes, and respiratory tract. Observe manufacturer’s WARNING labels; Material Safety Data Sheet (MSDS) instructions for proper handling, storage, and disposal; and current safety directives. Use cleaners/ chemicals only in authorized areas. Discard soiled cloths into approved safety cans. Consult the local Bioenvironmental Engineer for specific protective equipment and ventilation requirements. • USE OF RESPIRATORS. Dry developer particles are not toxic materials. However, like any solid foreign matter, they SHALL NOT be inhaled. Air cleaners, facemasks, or respirators may be required. The Base Bioenvironmental Engineer SHALL be consulted if the process generates airborne particles. • EXPOSURE TO SF6 GAS. Exposure to excessive amounts of Sulphur Hexafluoride (SF6) gas can cause asphyxiation by displacing oxygen in the air. Care SHALL be taken not to release large quantities of SF6 gas into unvented work areas. The amount leaked into the air while performing normal X-ray tube repair does not create an asphyxiation hazard. When SF6 is heated, it liberates hazardous fluorine gas into the air. This possibility of producing fluorine gas exists in most X-ray tube heads. Precautions SHALL be taken to guard against the inhalation of the gas released from X-ray tubes that have been energized.
x
T.O. 33B-1-2 • IMPROPER CLEANING PROCEDURES. Improper cleaning procedures/materials can cause severe damage to the material under inspection. Preparation of parts to include but not limited to paint removal and chemical etching SHALL be accomplished by maintenance personnel who are properly trained, highly skilled, and experienced in those particular specialties and are aware of the effects on the part/material due to the use of these chemicals and methods. T.O. 1-1-691 applies to the Air Force, T.M. 1-1500-344-23 applies for the Army; and N.A. 01-1A-509 applies for the Navy and Marine Corps. • PRECAUTIONS DURING RADIOGRAPHIC INSPECTIONS. Exposure to excessive X or gamma radiation is harmful to personnel and especially an unborn fetus. All applicable safety precautions SHALL be complied with. While most X-ray equipment is designed to minimize the danger of exposure to direct or stray radiation, certain precautions SHALL be observed. Failure to comply with safety procedures may result in serious injury to personnel. Coordinate all operational changes with the Base Radiation Safety Officer. Radiation protection requirements are discussed further in (see T.O. 33B-11) for additional safety information. (NAVY ONLY: Radiation safety guidance is provided by NAVSEA S040-AARAD010.) • PRECAUTIONS DURING PENETRANT INSPECTIONS. Penetrant inspection includes the use of black light and exposure to flammable chemicals that may affect skin, eyes, and respiratory tract. Care SHALL be exercised when using hot black lights so as not to burn hands, arms, face, or other exposed body areas. Wear nitrile, neoprene, or other approved gloves and keep the insides of gloves clean when handling penetrant materials. When processing parts through chemicals in the stationary lines, chemical goggles, rubber apron, and protective gloves SHALL be worn. During times of portable inspection, a minimum of protective gloves and eye protection SHALL be worn. Consult your local Bioenvironmental and Safety offices for further guidance. Ensure the Base Bioenvironmental Office performs an adequate surface area exhaust ventilation evaluation annually. When recommended by the Base Bioenvironmental Engineer, an approved respirator SHALL be worn when working in areas where adequate ventilation cannot be practically provided. The use of visible dye penetrant is PROHIBITED on engine, aircraft, and missile parts except for those with specific engineering approval for each inspection. • Magnetic particle inspection includes exposure to chemicals, ultraviolet light, and electrical current. Rubber insulating floor matting, rated for the voltage of the equipment being worked on, SHALL be used in front of magnetic particle units. Care SHALL be exercised when using hot black lights so as not to burn hands, arms, face, or other exposed body areas. Wear nitrile, neoprene, or other approved gloves and keep the insides of gloves clean when handling magnetic particle materials. When processing parts through chemicals in the stationary lines, chemical goggles, rubber apron, and protective gloves SHALL be worn. During times of portable inspection, a minimum of protective gloves and eye protection SHALL be worn. Consult your local Bioenvironmental and Safety offices for further guidance. Ensure the Base Bioenvironmental Office performs an adequate surface area exhaust ventilation evaluation annually. 6.
ACCESS TO SURFACES AND PART PREPARATION.
Access to aircraft surfaces (e.g. panel removal) requiring Nondestructive Inspection, SHALL be accomplished by maintenance personnel who have properly documented training and are highly experienced in those particular specialties. Improper cleaning procedures/materials can cause severe damage to the material under inspection. Preparation of parts to include, but not limited to, paint removal and chemical etching SHALL be accomplished by maintenance personnel who are properly trained, highly skilled, and experienced in those particular specialties and are aware of the effects on the part/material due to the use of these chemicals and methods. T.O. 1-1-691 applies for the Air Force, T.M. 1-1500-344-23 applies for the Army, and N.A. 01-1A-509 applies for the Navy and Marine Corps.
xi/(xii Blank)
T.O. 33B-1-2
CHAPTER 1 NONDESTRUCTIVE INSPECTION METHODS, GENERAL INFORMATION SECTION I INTRODUCTION 1.1
INTRODUCTION.
1.1.1 Purpose. Nondestructive Inspection (NDI) is the inspection of a structure or component in any manner that will not impair its future usefulness. The purpose of the inspection may be to detect flaws, measure geometric characteristics, determine material structure or composition, or it may characterize physical, electrical, or thermal properties without causing any changes in the part. The five standard NDI disciplines include: • • • • •
Liquid Penetrant Magnetic Particle Eddy Current Ultrasonic Radiography
1.1.2 Scope. This publication contains general procedures and process controls for NDI methods and SHALL be used only when specific inspection instructions are not available and as test part geometry, material, coating, and surface finish permits. It is intended that these general procedures be used as directed and with guidance from an NDI Level 3 or the engineering authority for the weapon system or commodity item being tested. The procedures in this manual can be used as a stand-alone inspection instruction when T.O. 33B-1-2, T.O. 33B-1-1 or a MIL Standard is referenced as the inspection document, or when no specific inspection criteria exist. The general procedures are written for use by an experience level 2 or equivalent (5-level) technician. In some instances, an experienced task certified level 1 or equivalent (3-level) technician can effectively use the general procedures. It is recommended that an experienced level 2 or higher technician thoroughly review the procedures with the task certified level 1 technician prior to approving use in an actual inspection. The process control procedures are written so that a level 1 or equivalent (3-level) technician can perform the checks with limited training and supervision. Guidance for development of NDI procedures is contained in MIL-DTL-87929C, Appendix F. NDI procedures contained in this manual are detailed step-by-step instructions with illustrations so a qualified NDI technician can perform the required inspection. In addition, this manual provides some general safety guidance for NDI inspectors. Other safety guidelines may apply and SHALL be used as required. 1.1.3 Format of Procedures. Though MIL-DTL-87929C is a directive for NDI Work Packages, it provides the proper format for detailed/repetitive NDI procedures. To ensure continuity of inspections, all on and off equipment maintenance NDI manuals (e.g. -9, -36, etc.) SHALL be written to adopt the special requirements of MIL-DTL-87929C into MIL-PRF83495 when writing NDI procedures for these maintenance manuals. An individual qualified and certified to Level 3 in accordance with NAS 410 in the inspection method being used, SHALL approve all written procedures. 1.1.4 Knowledge of NDI. NDI methods in the hands of a trained and experienced technician are capable of detecting flaws or defects with a high degree of accuracy and reliability. It is important maintenance-engineering personnel are fully knowledgeable of the capabilities of each method but it is equally important they recognize the limitations of the methods. Rarely should an NDI method ever be considered conclusive. Often but not always, a defect indication detected by one method must be confirmed by another method to be considered reliable. The equipment is highly sensitive so the limits for acceptance and rejection are as much a part of an inspection as the method itself. As an example, ultrasonic inspection criteria must be designed to overlook these ‘‘normal’’ indications and to discriminate in favor of the discontinuities that will affect the service of the component. 1.1.5 NDI Points-of-Contact. To fully utilize the content of this Technical Order it may become necessary to contact members of the Air Force NDI engineering community for technical guidance. The following points-of-contact are current at the time of publishing. • Chief, Air Force NDI Program Office, AFRL/MLS-OL. DSN: 339-4322, Comm: 405-739-4322. • ALC NDI Program Manager. Oklahoma City Air Logistics Center. DSN: 336-5008, Comm: 405-736-5008. • ALC NDI Program Manager. Ogden Air Logistics Center. DSN: 586-4496, Comm: 801-586-4496. 1-1
T.O. 33B-1-2 • ALC NDI Program Manager. Warner Robbins Air Logistics Center. DSN: 468-4489, Comm: 912-926-4489. • NDI Field Program Manager. Air Force NDI Program Office, AFRL/MLS-OL. DSN: 339-3768, Comm: 405-7393768. • Technical Content Manager 33B series Technical Orders. Air Force NDI Program Office, AFRL/MLS-OL. DSN: 8841880, Comm: 405-734-1880.
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T.O. 33B-1-2
SECTION II PROCESS CONTROLS 1.2
PROCESS CONTROLS. NOTE Specific process controls are discussed in section two of Chapter 2 through Chapter 6 of this manual.
1.2.1 Reason for Controlling the Process. Process control is an essential ingredient in achieving consistent and reliable results with NDI inspections. A well regimented NDI process control program will not allow conditions to develop that render inspection methods as a source of misinformation. This misinformation may take two forms: 1) When NDI determines a part is defective, when in truth it is not, resulting in a false call. This is a waste of resources and an unnecessary reduction in mission capability. 2) Even more dangerous is determining a part to be serviceable when in fact it is defective resulting in a missed call. Both forms of misinformation can be minimized through the implementation of effective process control. 1.2.2 Scope of Process Control. All aspects of these categories are interrelated. They have to be tuned to each other to achieve valid inspection results. If any one of these requirements is altered, the final outcome of the inspection will change, regardless of the inspector’s proficiency. 1.2.2.1 Process control is a general term used to encompass the actions and documentation required by established directives and logic. These controls are necessary for an NDI method to be effective in detecting conditions of interest (e.g., cracks, foreign objects, corrosion, alignment of parts, and thickness of parts). 1.2.2.2 Areas that fall within the scope of process control are as follows: • • • • • •
Training and the demonstrated practical skills of inspectors. Inspection environment. (e.g., temperature, specific type and levels of light, safety, and human engineering.) Material control. (e.g., serviceability of ultrasonic transducers, eddy current probes, penetrant materials, X-ray film and chemicals, and magnetic particle suspensions.) Equipment control. (e.g., operational and performance capability or Test Measurement Diagnostic Equipment (TMDE)/user calibration.) Written inspection instructions. (e.g., adequate, -9, -26, and -36 technical orders and Time Compliance Technical Orders (TCTOs).) Adherence to written inspection instructions. (e.g., distinguishing requirements dictated by specific NDI procedures versus commonly accepted basic NDI practices.) Table 1-1.
Frequency for Process Control
Liquid Penetrant System Performance Test (Cracked Chrome Panels) System Performance Test (Starburst-PSM) (Depot Only) Water Wash Pressure Water Wash Temperature Black Light Intensity Inspection Booth Cleanliness Penetrant Contamination Developer Contamination (Aqueous: Soluble and Suspendable) Developer Coverage (Aqueous: Soluble and Suspendable)
Interval Weekly
Para 2.2
Daily
2.3
Daily or Prior to Daily or Prior to Daily or Prior to Daily Daily or Prior to Daily or Prior to
Monthly
use use use use use
2.12 2.12 3.2.6 2.4 2.9.2 2.10.2 2.10.4 2.10.5 2.10.1
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T.O. 33B-1-2 Table 1-1.
Frequency for Process Control - Continued
Liquid Penetrant Dry Developer Condition
Penetrant (Method A) Water Contamination Lipophilic Emulsifier Performance Test Hydrophilic Remover Concentration Hydrophilic Remover Performance Test Developer Concentration (Aqueous: Soluble and Suspendable) Ambient White Light Drying Oven Calibration Magnetic Particle Testing Concentration/Suspension Settling Test Vehicle Fluorescence Test System Effectiveness Test and In-use Field Indicator Check Ambient Light Check Black Light Intensity Amperage Indicator Check Quick Break Water Break Test (Water Baths Only) Dead Weight Eddy Current Probe/Slot Test Ultrasonic Inspection Vertical Linearity Horizontal Linearity Sensitivity Check Resolution Check Dead Zone Check Angle Beam Point of Incident Angle Beam Angle Determination Angle Beam Skew Angle Radiography Inspection Safelight Fog Evaluation Interlock Functional Check Interlock System Inspection Safe Light Filter Check Fixer Control Development Process
1-4
Interval Daily or Prior to use
Monthly Monthly Monthly Monthly Monthly 60 Days IAW T.O. 33K-1-100-CD-1 Interval Prior to use and after 8- hours of continuous use In Conjunction with Concentration/Suspension Settling Test Weekly 60 Days Daily or Prior to use 90 Days 90 Days Daily or Prior to use 90 Days Interval 180 days Interval Quarterly Quarterly Quarterly Quarterly Quarterly Quarterly Quarterly Quarterly Interval Initial install and requirements described in indicated paragraphs Prior to X-ray operation 180 Days Monthly Monthly Weekly
Para T.O. 33B-1-1 2.6.8.7.1 2.6.10.4.9.2 2.7 2.8 2.9 2.9.3 2.10 2.10.3 3.2.6.1 T.O. 33B-1-1 Para 3.2.8 3.2.9 3.2 3.2.12 3.2.6.1 3.2.6 3.2.3 3.2.4 3.2.11 3.2.5 Para 4.2 Para 5.1.1 5.1.2 5.1.3 5.1.4 5.1.4.2 5.1.7 5.1.9 5.1.8 Para 6.1 6.1.6 6.1.6 6.1.5 6.1.4 6.1.3
T.O. 33B-1-2
CHAPTER 2 FLUORESCENT LIQUID PENETRANT INSPECTION SECTION I FLUORESCENT LIQUID PENETRANT INSPECTION GENERAL PROCEDURE 2.1
FLUORESCENT LIQUID PENETRANT INSPECTION GENERAL PROCEDURE.
Fluorescent penetrant inspection is an effective method for detecting surface breaking discontinuities in metallic parts. It can provide excellent detection sensitivity; however, the effectiveness of the method is highly dependent on strict control of the process. Penetrant material SHALL be listed on QPL SAE AMS 2644 and process control requirements must be followed. Black lights SHALL be capable of producing ultraviolet light intensity of at least 1000 micro-watt per square centimeter and SHALL NOT emit more than 2 ft-candles of white light. Ultraviolet and white-light measurements SHALL be measured 15 inches from the lens. Ambient light conditions SHALL be as low as possible when performing inspections under black light illumination. The ambient light SHALL NOT exceed 2 ft-candles in an inspection booth. Test part surfaces SHALL be free of coatings and contaminants. Inspectors SHALL meet the training and certification requirements stated in paragraph 1.2 of T.O. 33B-1-1. Table 2-1.
♦ ♦ ♦ ♦ ♦
Fluorescent Penetrant Advantages and Limitations
Advantages Capable of complete coverage of complex shapes Capable of detecting small surface discontinuities Is effective on ferrous and nonferrous metals and a variety of other materials Inexpensive and requires less training than other methods Readily adaptable to large volume processing
♦ ♦ ♦ ♦ ♦
Disadvantages/Limitations Flaw opening must be open at the surface of test part Surface condition must be relatively smooth and free of coatings and contaminants Effectiveness is highly dependent on process control and cleanliness of inspection surface Surface coating removal procedures affect process sensitivity (when possible coating removal SHOULD be limited to chemical stripping processes) Cannot perform inspections with part temperature below 40°F or above 125°F
2.1.1 Preparation of Part. WARNING • Due to the oily nature of most penetrants, they SHALL NOT be used on parts, such as assemblies, where they cannot be completely removed and will subsequently be exposed to gaseous or liquid oxygen. Oils, even residual quantities, may explode or burn very rapidly in the presence of oxygen. Only materials specifically approved for this application SHALL be used if penetrant inspection is required and complete removal of the residue is not possible. The applicable Weapons System Technical Order and/or the responsible ALC NDI Manager SHALL direct use of these materials.
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T.O. 33B-1-2 • Some penetrant materials may contain sulfur and/or halogen compounds (chlorides, fluorides, bromides, and iodides). These compounds may cause embrittlement or cracking of austenitic stainless steels if not completely removed prior to heat-treating or other high temperature exposure. Entrapped halogen compounds may also cause corrosion of titanium alloys if not completely removed after the inspection is completed and the part is subjected to elevated temperatures. The applicable Weapons System Technical Order and/or the responsible ALC NDI Manager SHALL direct use of these materials. • All relevant safety equipment and procedures directed by Chapter 2 Section VIII of TO 33B-1-1 and AFOSH Standard 91-501 are required in this inspection procedure and SHALL be adhered to. Correct part preparation is vital to consistent and effective penetrant inspection results. Coating removal SHALL be accomplished IAW applicable Technical Order procedures and performed by trained and certified personnel. CAUTION • Chlorinated hydrocarbon solvents such as trichloroethylene, trichloroethane, carbon tetrachloride, and Freon (including its use in aerosol spray cans) SHALL NOT be used on titanium. • Penetrant equipment contacting titanium such as parts-holding baskets SHALL NOT be coated with cadmium, lead, silver, or zinc. • Failure to comply with these cautions could have a detrimental effect to the structural capabilities of the components being prepared. NOTE When accomplishing penetrant inspections, the preferred finish removal method is chemical. If the finish must be removed by mechanical means, it is recommended an acid etch (0.0004 inch minimum removal) be performed prior to penetrant inspection. Trained and qualified personnel SHALL perform acid etching IAW the applicable 3 series Technical Orders. Some organizations may require acid etching; consult the applicable Weapons System Technical Order and/or the responsible Weapons System SPO. a. Have all surface coatings removed from the area to be inspected as required. Anodized coatings SHALL NOT be stripped from aluminum alloys. Refer to the applicable -23 series Technical Orders and the Structural Maintenance or Corrosion Control Shop for coating removal procedures. b. Perform a final wipe down of the part with a clean lint free cloth or paper towel dampened with an approved cleaner. 2.1.2 Penetrant Application Procedure. Penetrant methods C and D are the most common processes used at Air Force NDI laboratories and are covered in this procedure. Methods A and B penetrant procedures SHALL NOT be used unless specific approval and instruction is provided by the Weapon System SPO or the ALC NDI Manager. Minimum penetrant sensitivity levels are shown in Table 2-2. Most NDI Laboratories will use level 3 (High) sensitivity penetrant materials in their stationary penetrant process. Level 3 penetrant is generally adequate for most applications unless otherwise specified by technical order or engineering directive. If background fluorescence is noticeably high, a decrease in sensitivity level may be required. Titanium and some rotating engine parts require and ultra high-level penetrant sensitivity, small amounts of various penetrants may need to be purchased to meet the requirements of all test part materials. Various sensitivity level penetrants can easily be purchased in small quantities from any reliable NDI product distributor. Contact the appropriate ALC NDI Manager for assistance. Table 2-2.
Material and Minimum Penetrant Sensitivity Level
Materials Nonaircraft Rough Cast or Weld Magnesium and Aluminum Steels and Nickel Alloys Titanium and some rotating engine parts
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Penetrant Sensitivity Level 2 (Medium or Normal) 3 (High) 3 (High) 4 (Ultra High)
T.O. 33B-1-2 a. Apply the penetrant to the inspection area by brushing, swabbing or spraying (method C) or brushing, swabbing, dipping, flowing or spraying (method D). Reapply penetrant as necessary to prevent the penetrant from drying during the dwell. b. Allow penetrant to dwell for the minimum time defined in (see Table 2-3). The drain dwell mode is the preferred method of penetrant dwell; the immersion dwell mode is used as directed by a specific inspection instruction. Table 2-3.
Penetrant Dwell Times
Temperature 40 – 60°F Service Induced Fatigue Cracks Stress Corrosion Cracks Temperature 60 – 125°F Service Induced Fatigue Cracks Stress Corrosion Cracks
Minimum 60 minutes 240 minutes Minimum 30 Minutes 240 Minutes
2.1.3 Penetrant Removal Procedure. During the penetrant removal process, it is important to remove all the surface penetrant without removing penetrant contained in defects. 2.1.3.1 Method C (Solvent Wipe) Penetrant Removal. CAUTION The solvent-remover SHALL NOT be applied directly onto the inspection surface to remove excess penetrant. a. Following the penetrant dwell period, the surface is wiped with a clean, dry lint-free cloth or towel to remove the major portion of surface penetrant. The proper procedure is to make a single pass and then fold the cloth or towel over to provide a clean cloth surface for each wipe. b. When the surface penetrant has been reduced to a minimum, remove any remaining residual penetrant using a clean lint-free cloth or towel lightly moistened with an approved solvent remover. The amount of solvent applied to the cloth is critical. The cloth is only lightly moistened with the application of a fine spray of solvent. The cloth SHALL NOT be saturated by pouring, immersion, or excessive spraying. c. A black light is used to examine the part surface during the intermediate and final wiping stages. The surface of the rag should also be examined under black light during the final solvent wipe. If the rag shows more than a trace of penetrant, it is folded to expose a clean surface, remoistened with solvent, and again wiped across the part. This step is repeated until the fluorescent background on the part is minimal and the rag shows little or no trace of penetrant. d. After the solvent wipe, conduct a final wipe down with a clean dry cloth or towel to remove any residual solvent remaining on the part surface. 2.1.3.2 Method D (Hydrophilic Remover) Penetrant Removal - Immersion. CAUTION The correct concentration of hydrophilic remover is critical to the Method D process. Consult the manufacturer’s guidelines for remover concentration criteria. Penetrant removal for Method D immersion begins with a clean water rinse. Depending on the complexity of the test part, the rinse should be between 30 and 120-seconds. Maintain a rinse angle of 45 to 70°, water temperature between 50 and 100°F, and water pressure below 40 psi.
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T.O. 33B-1-2 a. Following the pre-rinse, an immersion dwell in hydrophilic remover is used to remove the remaining surface penetrant. The remover is slightly agitated to allow fresh remover to be exposed to the part, this is usually accomplished with low-pressure shop air at the bottom of the remover tank. Agitation can also be accomplished by gently stirring the test part in the remover. Dwell times will vary between 30 and 120-seconds. If a predetermined dwell time is not available for the in-use remover, start with a 30-second immersion dwell and then perform the rinse. If the background is unacceptable perform another 15-second immersion dwell then rinse and repeat the procedure until the part has acceptably low background fluorescence. Total remover immersion SHALL NOT exceed 120seconds. b. After the immersion dwell, rinse the remover and remaining surface penetrant from the part. Perform the rinse under black light to the same criteria as the pre-rinse. Stop the rinse when background fluorescence is at a minimum. It is important to keep the immersion dwell and the water rinse to the lowest time possible and still obtain low background fluorescence. 2.1.3.3 Method D (Hydrophilic Remover) Penetrant Removal – Spray. CAUTION The hydrophilic remover concentration SHALL NOT exceed 5-percent when using spray application Penetrant removal for Method D spray begins with a clean water rinse. Depending on the complexity of the test part, the rinse should be between 30 and 120-seconds. Maintain a rinse angle of 45 to 70°, water temperature between 50 and 100°F, and water pressure below 40 psi. a. Following the pre-rinse, use a garden sprayer to spray a 5-percent concentration of hydrophilic remover onto the inspection surface. Perform remover application under black light illumination to ensure optimum penetrant removal. Care must be taken not to over-remove the surface penetrant. Maximum remover spray time SHALL NOT exceed 120 seconds. Use only the minimum spray time required to obtain low background fluorescence. b. A final water-only spray is used to remove the hydrophilic remover from the surface. Depending on the complexity of the test part, the rinse should be between 30 and 120-seconds. Maintain a rinse angle of 45 to 70°, water temperature between 50 and 100°F, and water pressure below 40 psi. 2.1.4 Developer Application and Drying Procedure. Developers are used to draw penetrant from discontinuities and spread it out over adjacent part surfaces increasing the visibility of the indication. Developers also provide a contrasting background for the penetrant material. 2.1.4.1 Dry Developer (Form a) Application. WARNING Dry developer particles are not toxic materials; however, inhalation should be avoided. Air cleaners, facemasks, or respirators may be required. The Base Bioenvironmental Engineer SHALL be consulted if the process generates airborne particles. NOTE • Dry developers SHALL NOT be used unless specifically approved by the applicable Weapons System Technical Order and/or the responsible ALC NDI Manager. • Dry developers SHALL NOT be applied to a part until the surface is thoroughly free of moisture. The presence of even a little moisture will interfere with the developer action and small flaws may be missed. a. Dry the test part completely before applying dry developer.
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T.O. 33B-1-2 b. Dry developer is applied by blowing with a bulb type blower, immersing in a container, pouring the powder over the part, use of a dust or fog chamber, or an electrostatic system. c. Shake or carefully blow off (with bulb type blower) the excess developer, if using compressed air it SHALL be below 5-psig. For small areas, a bulb type blower is recommended. d. Allow developer to dwell using the dwell times in (Table 2-4). 2.1.4.2 Water-soluble (Form b) Developer Application:. Water-soluble developer is the most commonly used developer at Air Force NDI laboratories. It is the recommended developer for method D penetrants because it provides a better background than dry or water suspended developers and does not require agitation. a. Apply water-soluble developer by dipping or flowing. Allow the part to drain and rotate to prevent developer pooling. b. Place the test part into a clean dryer oven with a temperature of 140°F or less. (Depots with automatic or semiautomatic systems SHOULD refer to the process order for the system or test part to set drying oven temperature.) Rotate the part as required to prevent developer pooling. c. Remove the test part from the drying oven as soon as the part is completely dry. d. Allow the developer to dwell. Dwell time begins when the test part is completely dry. (Refer to Table 2-4 for developer dwell times.) 2.1.4.3 Water-Suspended (Form c) Developer Application:. Water-suspended developers are applied in the same manner as water-soluble with one exception; suspended developers require thorough agitation prior to application to the test part. Refer to paragraph 2.1.4.2 for procedures. 2.1.4.4 Nonaqueous (Form d) Developer Application:. Nonaqueous solvent-suspended developers are generally packaged in aerosol spray cans. It is most often used in portable inspections but is also used in the bleed-back procedures for methods C and D. It provides an excellent background and is the most sensitive developer form. NOTE Nonaqueous developers SHALL NOT be applied to a part until the surface is thoroughly free of moisture. The presence of even a little moisture will interfere with the developer action and small flaws may be missed. a. Ensure the test part is completely dry before applying nonaqueous developer. b. Shake spray can thoroughly before use. c. Spray a light even coat of developer over the inspection area. d. Allow the developer to dwell. (Refer to Table 2-4 for developer dwell times.) e. Inspect the test part after sufficient dwell. NOTE Test parts SHOULD NOT be exposed to high intensity black light during the developer dwell. Long exposure to black light will cause penetrant indications to fade. Table 2-4.
Nonaqueous Developer (Spray Cans) Service Induced Fatigue Cracks Stress-Corrosion Cracks
Developer Dwell Times Temperature 40 – 60°F Minimum 20 minutes 60 minutes
Maximum 60 minutes 120 minutes
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T.O. 33B-1-2 Table 2-4.
Developer Dwell Times - Continued Temperature 40 – 60°F
Nonaqueous Developer (Spray Cans) Aqueous Developer (Water Soluble and Suspendable) Service Induced Fatigue Cracks Stress-Corrosion Cracks Dry Developer Service Induced Fatigue Cracks Stress-Corrosion Cracks Nonaqueous Developer (Spray Cans) Service Induced Fatigue Cracks Stress-Corrosion Cracks Aqueous Developer (Water Soluble and Suspendable) Service Induced Fatigue Cracks Stress-Corrosion Cracks Dry Developer Service Induced Fatigue Cracks Stress-Corrosion Cracks
Minimum
Maximum
Minimum 30 minutes 60 minutes Minimum 30 minutes 60 minutes Temperature 60 – 125°F Minimum 10 minutes 30 minutes
Maximum 120 minutes 120 minutes Maximum 240 minutes 240 minutes
Minimum 15 minutes 30 minutes Minimum 15 minutes 30 minutes
Maximum 60 minutes 120 minutes Maximum 120 minutes 240 minutes
Maximum 30 minutes 60 minutes
2.1.5 Fluorescent Penetrant Interpretation. Fluorescent penetrant interpretation is done under blacklight illumination in an inspection booth or darkened area. Portable inspections may require a locally manufactured or purchased tent-like apparatus made of dark cloth or canvas to reduce ambient light levels and enhance inspection sensitivity. Identify indications as linear or rounded and measure the largest dimension of the indication for comparison to acceptance criteria. A rounded indication has length that is less than 3 times its width. A linear indication has a length 3 or more times its width. Evaluate indications according to limits in technical data. If technical data is not specific or no technical data is available, consider all linear indications relevant and rounded indications 1/16th of an inch or larger relevant for both aircraft and nonaircraft test parts. 2.1.5.1 Defects will generally be linear or aligned rounded or pinpoint indications resulting from: • • •
Fatigue cracks. Stress corrosion cracks. Intergranular corrosion.
2.1.5.2 Non-relevant indications will not be marked. These indications can be identified by using the bleed-back method (see paragraph 2.1.6). Non-relevant indications are generally: • • • •
Scratches. Nicks. Tool marks. Machined marks.
2.1.5.3 Defects should be marked on the part surface with an approved marking pencil. Measure the defect and note identifying characteristics. Describe the defect in detail including its size (length), location, and orientation. Document inspection findings IAW Air Force Instructions and local directives. An example of a good defect description is as follows: ‘‘Method C penetrant inspection of welds on transfer case part number 128-6380. Crack noted and marked on the inlet to case weld. The indication is sharp, well defined, bright, and linear. The defect is 2.125 inches long and runs down the center of the weld crown.’’
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T.O. 33B-1-2
NOTE Air Force NDI personnel SHALL NOT make serviceability determinations except as described in AFI 21-101 (field units only). The role of the NDI inspector is normally limited to providing a detailed description of the defect and its location. Disposition and repair responsibility for a flawed part or airframe lies with Structural Maintenance personnel or the owning workcenter and the appropriate engineering authority. 2.1.6 Bleed-Back Method. The bleed-back method is used to evaluate discontinuities for relevance. Non-relevant indications such as scratches, nicks, and tool marks will generally not hold enough penetrant to redevelop indications after the initial indications have been removed. The following is a typical bleed-back procedure: a. Use a clean dry cloth or paper towel to wipe the indication area. b. Lightly dampen the corner of a clean cloth or cotton swab with an approved solvent remover. Carefully wipe the indication area once with the solvent dampened cloth or cotton swab. After the solvent has evaporated, examine the bare surface under black light illumination for evidence of the indication as it begins and continues to develop without developer applied. Use of a 5-10X magnifier is recommended. If redevelopment of the indication occurs, it is be considered a relevant indication. c. If no indication is observed apply a light coat of nonaqueous (form d) developer. d. Again, after the developer solvent has evaporated, carefully examine the surface under black light illumination for evidence of the indication as it begins and continues to develop with developer applied. Use of a 5-10X magnifier is recommended. Allow a minimum redevelop time as defined in Table 2-4. If redevelopment of the indication occurs, it is considered a relevant indication. Non-relevant indication should not demonstrate any redevelopment. 2.1.7 Post Cleaning. Penetrant and developer residues SHALL be completely removed prior to reapplication of the surface finish. Dry developers, as well as water soluble and suspendable developers, are removed easily with a warm water rinse. Penetrants used in these processes are removed with warm water and an approved mild detergent. A soft bristled bush is effective for recessed areas, and around fasteners and other obstacles. When performing portable inspection, penetrant and developer residues are removed by first wiping with a clean dry cloth or paper towel then wiping again with a cloth or paper towel dampened with an approved solvent.
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T.O. 33B-1-2
SECTION II FLUORESCENT LIQUID PENETRANT INSPECTION PROCESS CONTROL 2.2
SYSTEM PERFORMANCE TEST PROCEDURE - CRACKED-CHROME PANELS. CAUTION Use care in handling and storing the panels. Do not drop, hit, or place mechanical stress on the test panels. Do not attempt to bend or straighten the test panels. Do not expose the test panels to temperatures above 212°F (100°C). Thorough ultrasonic cleaning of cracked-chrome panels after each use is mandatory. The panels are easily damaged by rough handling or when dropped. Damaged or degraded panels SHALL be immediately replaced.
The cracked-chrome panels are used to evaluate the liquid penetrant system’s performance. They provide a side-by-side comparison of in-use liquid penetrant materials with a reference standard of the same material that was set aside prior to the material being put into service. The cracked-chrome panels readily show small or gradual changes in penetrant material sensitivity. Tests made with cracked-chrome panels do not provide useful information on background fluorescence caused by surface roughness or the ability of a liquid penetrant to reveal small cracks in the presence of severe background fluorescence caused by surface roughness or porosity. 2.2.1 Equipment and Materials Required for Cracked-Chrome Panel Test. Equipment and materials needed to perform the cracked-chrome panel test are listed below: • • • • • •
In-use penetrant, remover, and developer. Reference penetrant, remover, and developer. Small glass or paper containers. 2 each acid brushes or swabs. 2 each cracked chrome panels. (Cracked-chrome panels are delivered from the manufacturer in sets of two. These panels SHALL be used together and not substituted with any other panels. When one panel is damaged or degraded the whole set SHALL be replaced.) Hydrophilic fluorescent liquid penetrant line and associated equipment. (The cracked-chrome panel may also be performed with method A, B, and C penetrant material.) (See paragraph 2.2.6 thru paragraph 2.2.8)
2.2.2 Procedure for Cracked-Chrome Panel Test. a. Wipe the cracked-chrome panels with a clean lint free cloth dampened with solvent. Allow to dry and examine under ultra violet light. If residual penetrant is present, clean the panels in accordance with (see paragraph 2.11). b. Pour a small quantity of working bath material and reference material in separate glass or paper containers. To avoid contaminating the entire reference sample, the reference material SHALL NOT be applied to the cracked-chrome panel directly from its storage container. c. Apply penetrant by brushing, swabbing, or flowing. Brushing or swabbing is preferred since it permits better control over the quantity of penetrant applied. Use the working materials on one panel and the reference materials on the other. Use separate brushes or swabs for the working material and the reference. Allow the penetrant to dwell for 5minutes. d. Perform a pre-rinse of 20-seconds or less. Allow just enough time to remove the surface penetrant. (Coarse spray of plain water at no more than 40 psi with a water temperature between 50 and 100°F) e. Apply remover by immersing the panels in their correlating working bath and reference material. Removal time will be very short, between 10- to 20-seconds. f. Perform a final rinse of 20-seconds or less. (Coarse spray of plain water at no more than 40 psi with a water temperature between 50 and 100°F) g. Apply correlating working bath and reference developer by immersion, flowing, or spraying. (Ensure watersuspended developers are mixed well before applying.)
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T.O. 33B-1-2 h. Place in clean drying oven. Do not allow to sit in the dryer for an extended period, remove as soon as the panels are dry. i. Allow developer to dwell for 5-minutes. The dwell begins after the panels are completely free of moisture. j. Examine the panels side-by-side under black light, first noting the overall brightness and color of the indications. Second, examine each in detail by following individual indications across both panels. Note the presence, absence, or diminishing of crack indications on the working bath panel as compared to the reference sample panel and observe the difference in continuity, size and color. Any distinct difference SHALL be cause for additional testing to determine if the penetrant, remover, or the developer caused the difference in the indications. 2.2.3 Testing for Failed Penetrant. If the system performance test indicates a loss of sensitivity or brightness, use a set of clean, dry cracked-chrome panels to repeat the material test procedure (see paragraph 2.2.2) with the following changes: use the reference samples of remover and developer on both panels. If crack indications on the two panels show clearly visible differences in sensitivity, brightness or color, the penetrant SHALL be replaced. 2.2.4 Testing for Failed Emulsifier/Remover. If there is little or no difference in the crack indications during the penetrant performance test, clean the panels and repeat the performance test procedure to test the emulsifier/remover. Use reference penetrant on both panels and apply the working sample of remover to one specimen and reference remover to the other panel at the appropriate point in the process. Apply reference developer to both panels. If crack indications on the two panels show clearly visible differences in sensitivity, brightness or color, the remover SHALL be replaced. 2.2.5 Testing for Failed Developer. If there is little or no difference in the crack indications during the remover performance test, clean the panels and repeat the performance test procedure to test the developer. Use reference penetrant and remover on both panels and apply the working developer to one panel and the reference developer to the other panel at the appropriate point in the process. If crack indications on the two panels show clearly visible differences in sensitivity, brightness or color, the developer SHALL be replaced. 2.2.6 Lipophilic Penetrant Systems. The removal step is the only difference in performing the cracked-chrome panel test on a lipophilic process. Simply skip step d in the procedure and modify step e so that the panels are immersed in emulsifier and immediately removed. Allow the emulsifier to dwell for 10 to 20 seconds and proceed to step f. 2.2.7 Water Washable Penetrant Systems. For water washable systems the remover and developer steps need to be modified. Skip steps d and e, proceed to step f. Wash the panels as long as necessary to remove all visible penetrant. Do not over wash, the cracks on these panels are shallow and the trapped penetrant can be easily removed by over washing. Since aqueous developer cannot be used with water washable penetrants, a nonaqueous or a dry power developer must be used. Dry the panels in the drying oven and then spray a light even coat of nonaqueous developer on the panels or dip the panels in dry powder developer. Proceed to step i and finish the procedure. 2.2.8 Solvent Removable Penetrant Systems. Solvent removable penetrant systems (spray cans) do not require a 7day system performance test because the materials are not subject to reuse or degradation. The cracked chrome panel test is required before a new batch of material is put into to service. The material previously used becomes the reference so it is important to test the new material before the old material is completely used up. The remover and developer steps need to be modified; skip steps d, e, and f. The removal step is to wipe the panels with a separate clean dry cloth and then perform another wipe with a separate solvent dampened cloth, repeat the solvent wipe until no penetrant is visible. The developer application step is to spray a light even coat of nonaqueous developer on the panels. Proceed to step i and finish the procedure. 2.3
SYSTEM PERFORMANCE TEST WITH THE PSM STARBURST PANEL (DEPOT ONLY).
The system performance test utilizing the PSM panel is a daily check of the entire penetrant system. The panel’s polished half contains five star shaped cracks and is used to monitor changes in penetrant sensitivity, while the grit blasted half is used to test the removal process of the penetrant system. The PSM panel test is ideally suited for high volume workloads because it can be processed directly in the working material along with the first batch of parts at the beginning of the workday. Because the panel is used strictly with in-use penetrant materials, no reference standards are needed. Facilities with automatic or semi-automatic penetrant systems that do not use traditional working bath tanks SHALL use the PSM panel solely as their system performance test. Laboratories with traditional penetrant lines SHALL use the Cracked-Chrome Panel Test as their system performance test but MAY use the PSM panel as an optional test.
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T.O. 33B-1-2 2.3.1 Procedure for Performing the PSM Starburst Panel Test. NOTE Facilities using automatic or semi-automatic systems SHALL process the PSM panel as they would a routine test part. Times, temperatures, water and air pressures will vary accordingly. Consult the ALC NDI manger for specific guidance. a. Dip, brush, or spray the PSM panel with in-use penetrant. Use the same criteria as a test part with suspected fatigue cracks. Test at room temperature. (30-minute dwell time) b. Pre-rinse the PSM panel. (Coarse spray of plain water at no more than 40 psi for 30- to 120-seconds with a water temperature between 50 and 100°F) c. Immerse or spray PSM panel in remover. Use the same remover time as used to process a normal part. (30 to 120 seconds) d. Perform the final rinse. (Same criteria as in step b) e. Dip the PSM panel in developer. (If water suspended developer is used ensure the solution is mixed well before dipping the panel.) f. Place the PSM panel in the dryer oven and remove immediately once the panel is dry. (Dryer oven should be preheated to 140°F or less; facilities using automatic or semiautomatic systems refer to the process order for dryer oven temperature.) g. Let the panel dwell for 15-minutes. h. Inspect and evaluate indications on the PSM panel. 2.3.2 Response of PSM Panels. PSM Panels are manufactured to provide a minimum number of indications for each penetrant sensitivity level. The panels SHALL show, as a minimum, the number of indications permitted during calibration and listed as follows: Minimum Number of Indications: Sensitivity Level Level 1 and 2 Level 3 Level 4
Number of Indications 3 Indications 4 Indications 5 Indications
2.3.3 Reading PSM Starburst Indications. Examine the panel for the number of starburst indications as well as the brightness of the indications. The PSM panel test is a flaw indication quality comparison from one test to another and the inspector must be able to observe a difference in the panel’s appearance. An increased background fluorescence, decrease in the number of flaw indications, decrease in flaw indication definition, or decreases in brightness are all indicators of a penetrant process problem. For example if the developer is malfunctioning, crack centers may still be seen, but may not be as bright as normal. When using aqueous developers, the developer SHALL provide a uniform coating over the chrome surface. Failure of the aqueous developer to wet the chrome may mean the solution strength is low, or the wetting agent has degraded. Washability and background fluorescence must also be interpreted. The grit blasted side of the PSM panel is used for this purpose. High and ultra-high sensitivity systems leave a fluorescent background on the panel’s grit blasted area. Other systems may leave no background. Neither condition is alarming unless it represents a change from the normal system performance. Higher than normal background may indicate low remover concentration, short remover dwell time, or an ineffective pre-wash. Lower than normal background may indicate high remover concentration, excessive remover dwell time, or inadequate developer application. If a performance problem is noted, additional testing is required to determine the cause. For laboratories using a traditional hydrophilic penetrant line refer to (see paragraph 2.2.2) and perform the cracked chrome panel test to systematically eliminate each possible cause until the problem area is identified. For laboratories using semi-automatic are automatic systems each section of the system needs to be inspected to determine if the preset parameters are correct and all equipment is functioning normally.
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T.O. 33B-1-2 2.3.4 Cleaning PSM Panels. PSM Panels SHALL be thoroughly cleaned immediately after use in accordance with (see paragraph 2.11). In addition, PSM panels SHALL be wiped with a clean, lint free, solvent dampened cloth and examined under ultra-violet light for residual penetrant prior to use. If residual penetrant is present, perform a thorough cleaning again. NOTE PSM panel indications will degrade with handling and repeated use. Gradual changes in indication appearance are not readily noticed. Careful handling and thorough ultrasonic cleaning is mandatory. 2.4
INSPECTION BOOTH CHECKS. NOTE Inspection booth checks do not require documentation unless specifically stated else where in this Technical Order or other directives. The frequency of the checks are at the supervisor’s discretion unless otherwise directed by this Technical Order.
The inspection booth and process SHALL be checked to verify the following: a. Verify the inspection booth is of adequate size for the parts to be inspected. b. Verify the booth is not used to store parts, consumables, or standards. c. The inspection booth SHALL be cleaned frequently and background fluorescence from spilled penetrant kept to a minimum. d. Black light bulbs and filters SHALL be kept clean and ambient light levels checked when filters or bulbs are replaced. e. Check black light intensity and document at least once each day or prior to use. f. Inspect filters for fit and excessive dirt, developer, cracks, and chips. g. Position black lights so they do not shine into the technician’s eyes. 2.5
SURFACE WETTING TEST. a. Apply a small amount of penetrant with a cotton swab to the clean, shiny surface of commercially available aluminum foil. b. Allow penetrant to dwell for 10-minutes. c. The penetrant should wet the surface and not retract or form beads.
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PENETRANT BRIGHTNESS TEST - (DEPOT ONLY).
Perform this test on all Type I fluorescent penetrants as follows: a. Pour 10 milliliters of IN-USE penetrant into a graduated cylinder. Allow the penetrant to drain down the inside cylinder walls. Add or remove penetrant as required to achieve exactly 10-milliliters. Clean the outside of the cylinder. b. Fill the graduated cylinder to the 100 ml level with an acetone (Specification 0-A-51F). Stopper the cylinder and slowly invert the graduated cylinder several times to mix the contents. Do not shake or agitate the cylinder vigorously. c. Using tweezers, insert a quartered piece of filter paper into the cylinder mixture, withdraw the paper and set it aside to air dry for a minimum of 5-minutes. d. Discard the contents of the graduated cylinder and clean the cylinder with an approved solvent (Specification O-C265 or equal). Dry with clean filtered compressed air.
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T.O. 33B-1-2 e. Pour 10 ml of REFERENCE SAMPLE penetrant into the graduated cylinder. Allow the penetrant to drain down the inside cylinder walls. Add or remove penetrant as required to achieve exactly 10 ml. Clean the outside of the cylinder. f. Fill the graduated cylinder to the 100 ml level with acetone. Stopper and slowly invert the graduated cylinder several times to mix the contents. Do not shake or agitate the cylinder vigorously. g. Using tweezers, insert a quartered piece of filter paper into the cylinder mixture, withdraw the paper and set it aside to air dry for a minimum time of 5-minutes. h. When both filter papers (in-use and reference) are dry, compare the fluorescent brightness of the filter papers to each other under black light. If a noticeable difference of fluorescent brightness is noted, the fluorescent properties of the in-use production line penetrant have deteriorated and the fluorescent sensitivity will probably not be acceptable. Follow accepted activity standards to process and perform additional testing or to discard the contaminated/degraded material. i. At the conclusion of the fluorescent brightness testing, rinse the cylinder with water, and clean with acetone. Dry with clean filtered compressed air. 2.6.1 Penetrant Rapid Brightness Test (FIELD LABS). A rough check of penetrant baths can be accomplished by comparing their appearance on an absorbent material, preferably filter paper. Perform this test on all Type I fluorescent penetrants as follows: a. Place a drop of the working bath penetrant on the absorbent material, preferably the filter paper. b. Place a second drop of penetrant from the reference standard on the same absorbent material near the drop from the working bath. c. When the two drops merge, examine under a black light for difference in color and brightness. If significant difference in color and brightness is noted additional testing is required. (See paragraph 2.2.3) 2.7
TESTING CONCENTRATION OF WATER BASED (METHOD ‘‘A’’) PENETRANTS.
There is a small number of approved Method ‘‘A’’ penetrants currently containing water as a major component. The few approved water washable penetrants are formulated to provide a similar sensitivity performance as Method ‘‘B’’ or ‘‘D’’ penetrants. Some savings may be realized in disposal cost of the more environmentally friendly penetrants. It should be noted that any penetrant that has been in-use SHOULD be tested for contaminants prior to disposal. It is not unusual for hazardous material, mainly heavy metals to build up in in-use penetrants from test parts and lubricants. Because water is a main constituent and evaporation losses may affect the penetrant performance, a periodic water concentration check is required. The refractometer method described in (see paragraph 2.9) SHALL be used to check concentration of water-based penetrants in the absence of specific manufacturer procedures. If the manufacturer provides specific water concentration test procedures the manufacturer’s procedures SHALL take precedent. 2.8
TESTING LIPOPHILIC EMULSIFIER (METHOD ‘‘B’’).
Penetrant is an unavoidable contaminant of lipophilic emulsifier. It is carried into the emulsifier on the surface of parts where it dissolves and is washed off during immersion and drain process. Since emulsifier and penetrant are capable of being mixed in all concentrations, even small quantities of fluorescent dye will cause the emulsifier to fluoresce. The fluorescent brightness increases with increasing dye content, but it is impossible to visually estimate penetrant contamination by observation of the tank surface. Emulsifier will continue to function when contaminated with penetrant; however, when the penetrant concentration reaches a certain level the emulsification action slows and eventually stops. The penetrant material specification (SAE-AMS-2644) requires a 4-to-1 mixture of emulsifier to penetrant to leave no more residual background than the uncontaminated emulsifier.
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T.O. 33B-1-2 2.8.1 Lipophilic Emulsifier Removability Test. NOTE The annealed type 301 or 302 stainless steel panel may be locally manufactured. It is a two-inch by four-inch, 16gauge (0.060) panel. The panel SHALL be ultrasonically cleaned or vapor degreased and grit blasted on both sides using 100 mesh, aluminum oxide grit (not beads), using 60 psig air pressure, with the gun held approximately 18- inches from the panel surface. After blasting, the panel SHALL be ultrasonically cleaned in acetone or other suitable solvent. Ensure the panel is dry and free of residues after cleaning. Handle the panel by the edges and protect it from contamination by wrapping in tissue paper. Locally manufacture a simple stand large enough to hold the panel and maintain a 60° (±15°) angle. The stand will prevent pooling during dwell. 2.8.1.1 The removability test requires using the annealed type 301 or 302 stainless steel panel. In-use lipophilic emulsifiers SHALL be periodically tested for contamination in accordance with (see Table 1-1). The process for performing the removability test is as follows: a. Immerse the panel in the working penetrant bath and allow it to drain for 10- minutes at approximately a 60° (±15°) angle. b. After the 10-minute dwell, apply working bath emulsifier to one-half of the panel and reference standard emulsifier to the other half. Immersion is the preferred method of application because it is better controlled. Pouring may be done but care must be taken to not mix or overlap the two emulsifiers. c. Allow emulsifier to dwell for 2-minutes then wash for 60-seconds. Maintain an even distance and angle when spraying the panel. Examine the panel for signs of fluorescent background after the rinse. d. Apply developer and place in a clean dryer oven. Remove the panel as soon as it is dry. e. Allow developer to dwell for 5-minutes. f. Evaluate the panel under black light. A distinct difference in residual background indicates excess penetrant contamination of the working bath lipophilic emulsifier. Should the emulsifier fail the contamination test, it SHALL be replaced with fresh material. NOTE A portion of in-use emulsifier (25 to 50 percent) MAY be extracted from the tank and replaced with fresh emulsifier. This procedure can be accomplished only one time in the service life of the emulsifier. A complete change out of the emulsifier is required once penetrant contamination again reaches unacceptable levels. A contamination check SHALL be performed after a partial change out of emulsifier. 2.9
HYDROPHILIC REMOVER REFRACTOMETER TEST.
The refractometer test is the preferred method for measuring the concentration of hydrophilic remover baths. The test is performed as follows: a. Dip the plastic rod supplied with the refractometer into the in-use hydrophilic remover. b. Raise the cover plate on the refractometer and place two or three drops of the test solution on the prism face. Close the cover plate; making certain the test solution film completely covers the prism face. c. Hold the refractometer close to a bright light source so light enters and illuminates the prism. Look through the eyepiece of the refractometer and read the Brix value (refractive index units) where the bright and dark areas meet. Adjust the position between the light source and the prism face to create a clearer meeting line. d. Record the refractive index units as indicated. Using the manufacturer’s literature, determine the concentration of the test sample from the refractive index value. Compare this value with the graph you created when mixing the bath. The working bath solution SHALL be within 5-percent of the required concentration. Adjustments are made by either adding water or concentrate remover to bring the remover bath concentration to an acceptable level.
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T.O. 33B-1-2 e. When the test has been completed, clean the refractometer cover plate and prism face with a soft lint-free cloth. 2.9.1 Hydrophilic Remover Hydrometer Test. A hydrometer may be used if recommended by the manufacturer of the hydrophilic remover. The hydrometer test involves the use of a hydrometer to determine the concentration of a solution by specific gravity. This method is very similar to the method used to check water-soluble and water-suspendable developers. When using the hydrometer, perform a water concentration test in accordance with the following procedure: a. Mix a reference sample of new hydrophilic remover as recommended by the manufacturer in a 500 ml graduated cylinder or similar container. b. Using the hydrometer, check the concentration of the reference sample by noting its specific gravity and recording this reading. c. Place the hydrometer in the working bath; read and record the test results. Compare the results of the reference standard and the in-use remover. The in-use remover is adjusted to achieve a concentration within 5-percent of the reference standard test results. 2.9.2 Hydrophilic Remover Quick Test for Penetrant Contamination. The quick test will determine if penetrant is present in the remover in large enough quantities to become a possible contaminant. Perform this test by passing a black light over the surface of the remover in the tank and visually examining it for signs of fluorescence. Penetrant is removed by skimming or absorbing the penetrant with a paper towel. 2.9.3 Hydrophilic Remover Performance Check. NOTE The immersion removal time cited in the following procedure is typical. Time will depend upon type of penetrant, type of remover, agitation, and remover concentration. The time SHALL be determined at each depot or field laboratory for each system involved. Trials SHALL be accomplished using fresh or uncontaminated remover. The objective is to use the minimum time necessary to produce a background-free surface on the immersion panel when the remover is uncontaminated. A performance check will verify the concentration or contamination of used immersion hydrophilic remover baths. Residual penetrant from parts disperse in the remover, can cause problems when performing a color comparison check and skew the refractive index when performing the refractometer test. Performance testing will usually indicate a problem with the remover bath (e.g., penetrant contamination, unacceptable concentration) well before a refractometer measurement will indicate a problem. The performance test involves processing the two annealed type 301 or 302 stainless steel panels with different removal contact times and comparing the results using the following procedure: a. Immerse the panels in the working penetrant bath and allow it to drain for 10- minutes at proximately a 60° (±15°) angle. b. Process the first panel through a 10-second pre-rinse, 10-second drain, 20-second immersion in remover, 5-second drain, and 10-second rinse. c. Process the second panel through the same cycle except double the immersion time to 40-seconds in the remover. Examine both panels under black light. When the remover is fresh and uncontaminated, neither panel should exhibit any background fluorescence. As the penetrant level in the remover starts to build up, the short immersion time panel will begin to show some residual fluorescence while the longer immersion panel remains free of background. As the amount of penetrant in the remover continues to increase, the level of fluorescence on the short immersion panel stabilizes and the longer immersion panel begins to show some residual background. When the remover reaches its penetrant tolerance limit, there will be negligible difference in fluorescence background on the two panels. The remover SHALL be changed at this point. d. Clean the panels by ultrasonically cleaning in acetone or other suitable solvent. Refer to (see paragraph 2.11) for more information on cleaning process control panels. 2.9.4 Hydrophilic Remover Background Fluorescence Check. If the performance check does not indicate remover degradation, using the same panels, determine if penetrant is causing the background fluorescence by proceeding as follows:
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T.O. 33B-1-2 a. Immerse the panels in the working penetrant bath and allow it to drain for 10- minutes at approximately a 60° (±15°) angle. b. Process the first panel using a 10-second pre-rinse, 10-second drain, 30-second immersion in the working bath remover, 5-second drain, and a 10-second rinse. c. Process the second panel using the same procedures above, except this time use the reference remover. d. Examine both panels under a black light. e. If background fluorescence is present on both panels, the working bath penetrant is contaminated and SHALL be replaced. If the panel processed with the reference remover is free of background fluorescence, and the other panel exhibits any background fluorescence, then the determination can be made that the working bath remover has reached its penetrant tolerance limit and SHALL be replaced. f. Ultrasonically clean the grit blasted panels using the cleaning process described in (see paragraph 2.11). 2.9.5 Hydrophilic Remover Spray Solution Test. Remover spray is normally used only once with the solution being disposed of after contact with the part. Contamination of the working solution is not a problem; however, the aspirator injection system requires frequent checks to ensure that the proper concentration is produced. Measure the concentration of remover in the spray whenever the aspirator or water pressure valve is adjusted and at the intervals prescribed in (see Table 1-1). A measurement is also taken whenever an unexplained change in background fluorescence occurs. Test hydrophilic spray remover as follows: a. Check the hydrophilic remover touch-up spray concentration by one of the methods explained in (see paragraph 2.9 and paragraph 2.9.1). b. The concentration of the spray remover is much lower than immersion baths, and the results of the check will reflect this change. Important items to remember are: (1) If the hydrophilic remover touch-up spray is not of the same batch as used to generate the original concentration versus refractive index graph, then a new graph needs to be plotted. (2) Make sure the temperature of the touch-up remover is within the parameters of the instrument/graph being used or compensated for. 2.9.5.1 The system concept for penetrant-material SHALL apply to the hydrophilic remover used in the touch-up step of the penetrant inspection. The material being used in the immersion remover tank and the touch-up spray SHALL be of the same manufacturer and qualified as a penetrant system listed in the qualified products list in accordance with QPL SAE AMS 2644. 2.10
WATER-SUSPENDED DEVELOPER CONCENTRATION TEST. NOTE Prior to obtaining the hydrometer reading, fill the working solution to the proper working level (as previously measured and marked), thoroughly agitate, and check the tank for caked particles on the bottom and in the corners. Allow newly prepared solutions to set for 4-hours after mixing then agitate prior to testing. This aging period allows the developer particles to become wetted or saturated.
The reading from the hydrometer is compared to an accurate graph/conversion chart obtained from the supplier of the specific developer. The process for performing a concentration test is as follows: a. Place the hydrometer directly in the tank, ensuring it floats free, not touching the tank sides. The specific gravity is read from the scale on the hydrometer. It may be more convenient to take a sample from the tank using a long, narrow glass container such as a graduated cylinder, which is deep enough to float the hydrometer. b. Compare the reading from the hydrometer to the graph of specific gravity and make adjustments to the developer concentration as required. The developer concentration shall be maintained within 5-percent of the required concentration.
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T.O. 33B-1-2 2.10.1 Water-Suspended (or Soluble) Developer Coating Uniformity Test. Water-suspended developers do not perform properly unless they wet the part surface and form a smooth, even coating once it dries. Lumpy or thick areas will hide small indications, while uncoated areas will not provide developer action. Poor wetting is usually due to the addition of too much water, which is used to replace water losses caused by drag-out or by developer wetting agents degrading over time. Contamination by oily materials may also destroy the wetting agents. Use clean cracked-chrome panels and perform the coating test as follows: a. Apply the working bath developer to one half of the panel and the reference standard developer to the other half of the panel. (cracked chrome panel) b. Inspect for signs of non-wetting, such as formation of beads and pulling away from edges or crack locations. c. The panel SHALL then be dried and examined for even and complete developer coverage. If the panel exhibits signs of poor wetting or coverage perform the developer concentration check. If concentration is low add developer and retest. If the concentration is adequate and wetting and coverage is poor the wetting agent has degraded or the developer is contaminated. Perform the developer penetrant contamination check or change the developer. 2.10.2 Water-Suspended (or Soluble) Developer Penetrant Contamination Test. Water-suspended developer may also become contaminated with penetrant. Check for fluorescent penetrant dye contamination by visual examination of the bath surface while passing a black light over it. Uncontaminated developer appears dull white while fluorescent dye contamination will show up as specks of yellow-green, floating on the top of the bath. Low-levels of contamination can be skimmed off of the developer liquid surface. Baths that exhibit significant amounts of surface penetrant that cannot be completely separated must be replaced. 2.10.3 Water-Soluble Developer Concentration Test. NOTE There are a wide variety of materials available to formulate water-soluble developers; therefore, the specific gravity hydrometer readings versus concentration will vary more than they will for the water-suspended developers. A specific gravity reading with a hydrometer is used to check the concentration of water-soluble developers. The supplier can provide an accurate conversion chart for its particular developer. The process for performing a concentration test is as follows: a. Place the hydrometer directly in the tank, ensuring it floats free, not touching the tank sides. The specific gravity is read from the scale on the hydrometer. It may be more convenient to take a sample from the tank using a long, narrow glass container such as a graduated cylinder, which is deep enough to float the hydrometer. b. Compare the reading from the hydrometer to the graph of specific gravity and make adjustments to the developer concentration as required. 2.10.4 Dry Developer Contamination Test. Dry developers are periodically checked for evidence of contamination by performing the following: a. Test for penetrant contamination by examining the developer under black light, while stirring or mixing the drypowder. b. Visually examine for moisture while stirring or mixing the dry-powder and checking for evidence of clumps. It may be possible to dry the powder if the water content is low by removing the lumps of developer and crushing it into loose flakes. If it is not possible to restore the original consistency, the developer SHALL be discarded. NOTE For dry developer that is recycled, ten or more fluorescent specks observed under black light in a 4-inch (10-cm) diameter circle when a sample is spread into a thin layer on a clean flat surface, is unsatisfactory. Penetrant contaminated dry developer SHALL be discarded.
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T.O. 33B-1-2 2.11
CLEANING PROCEDURE FOR PROCESS CONTROL TEST PANELS.
Process control panels (cracked-chrome panels, PSM panels, 301/302 stainless steel panels) SHALL be cleaned after use in accordance with the following steps: a. Clean the panels using soap and water and a soft natural bristle brush. Some handling or touching of the panel surfaces may be necessary, but SHALL be kept to a minimum to reduce fingerprint contamination. b. Ultrasonically clean the panels in isopropyl alcohol for 10-minutes. c. Ultrasonically clean the panels in acetone for a minimum of 10-minutes. Acetone may not be available in all laboratories; a 20-minute ultrasonic cleaning in isopropyl alcohol is acceptable substitute for the two 10-minute cleaning steps. d. Allow the panels to air dry. e. Examine the panels under black light for evidence of entrapped penetrant residues. If residues remain, repeat the cleaning process. 2.12
WATER PRESSURE AND TEMPERATURE CHECK.
Regular line pressure and water temperature is sufficient for penetrant inspections. Normal water line pressure is 10-40 psi and is checked prior to processing test parts or performing process control procedures. Normal line water temperature between 50 and 100°F (10 and 37.8°C) is adequate for penetrant procedures and is checked prior to processing test parts or performing process control tests. NOTE Black and white light process control requirements for Fluorescent Penetrant and Magnetic Particle are identical. Please refer to paragraph 3.2.6 for black and white light process control checks.
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T.O. 33B-1-2
CHAPTER 3 FLUORESCENT MAGNETIC PARTICLE INSPECTION SECTION I FLUORESCENT MAGNETIC PARTICLE INSPECTION GENERAL PROCEDURE 3.1
GENERAL MAGNETIC PARTICLE PROCEDURES.
Fluorescent magnetic particle inspection can produce excellent results when performed correctly. Strict control of process conditions is essential for successful inspections. Magnetic particle material SHALL meet the requirements of AMS 2641, 3045, or 3046, and successfully pass process control procedures prior to use. Black lights SHALL be capable of producing ultraviolet light intensity of at least 1000-micro-watts per square centimeter at a distance of 15-inches. Ambient light conditions SHALL be as low as possible when using black lights, not to exceed 2 foot-candles in an inspection booth. Test part surfaces SHALL be free of thick or uneven coatings and contaminants. Inspectors SHALL meet the training and certification requirements stated in paragraph 1.2 of T.O. 33B-1-1. Table 3-1.
Fluorescent Magnetic Particle Advantages and Limitations
Advantages ♦ Capable of complete coverage of simple shaped parts ♦ ♦ ♦ ♦ ♦
Detects very small surface and some subsurface discontinuities Effective on ferrous material
Inexpensive and requires less training than other methods Readily adaptable to large volume processing In some cases requires less surface preparation than Liquid Penetrant Inspections
Disadvantages/Limitations ♦ Complex shaped parts with varying material thickness require multiple shots and may produce indications at cross-sections, dissimilar metals, plating breaks, and overlaps ♦ Surface condition must be relatively smooth and free of thick or uneven coatings and contaminants ♦ Surface coating removal procedures affect process sensitivity (when possible SHOULD be limited to chemical removal processes) ♦ Cannot perform inspections on nonferrous material
3.1.1 Required Equipment and Materials. Material for Magnetic Particle Inspections must meet the requirements of AMS 2641, 3045, or 3046, as applicable. Only fluorescent oil-suspended material SHALL be used for inspections performed using the procedures in this Technical Order. Other materials such as powder or water-suspended vehicles both visible and fluorescent may be beneficial under unique circumstances and SHALL be approved for use on an individual application basis by the appropriate ALC NDI Manager. Stationary or portable equipment SHALL be listed in AS-455 or approved on an individual application basis by the appropriate ALC NDI Manager. 3.1.2 Preparation of Part. Proper part preparation is essential to a successful magnetic particle procedure. Most parts will require coating removal. Paint or chrome plating thicker than 0.003 inches SHALL be removed. Ferromagnetic coatings such as electroplated nickel greater than 0.001 inches SHALL be removed. All sealant SHALL be removed. If coatings are nonconductive, they SHALL be removed where electrical contact is made. A surface coating that is uneven, broken, or marred SHALL be removed. Generally, light even coatings of primer do not require removal. All dirt, oil, or grease SHALL be removed. Refer to the applicable -23 series Technical Order and the Structural Maintenance or Corrosion Control shop for coating removal procedures. 3.1.2.1 Parts SHOULD be disassembled as much as practical to allow access to all part surfaces and to prevent magnetic particle indications from forming at press or close fitted areas.
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T.O. 33B-1-2 a. Demagnetize the test part to ensure any residual magnetic field does not affect the inspection procedure. b. Perform a final wipe down of the part with a clean lint free cloth or paper towel dampened with an approved cleaner. 3.1.3 Selecting Type of Magnetizing Current. Selecting the type of current and method of application is critical to an effective procedure. Alternating current (AC) is very effective for detecting defects open to the surface like fatigue cracks. AC SHALL NOT be used when test parameters, crack orientation, and test specimen construction are not known. AC is best used with the wet continuous particle application method. Defects sought with AC must be open to the surface and most surface coating particularly plating must be removed. Direct current (DC) or more correctly, a rectified AC current (HWDC) is effective for locating both surface and subsurface defects and is used extensively on welds or when surface and/or subsurface defects are sought. HWDC is the preferred magnetizing current for residual inspections but is most effective with the wet continuous method of particle application. 3.1.4 Longitudinal Magnetization (Coil Shots). CAUTION Discontinuities can be difficult to detect when they propagate at angles less than 45° to the direction of magnetization. To ensure complete coverage of the test part each part SHALL be magnetized in at least two directions at right angles to each other. This may be accomplished with circular magnetization in two or more directions, or both circular and longitudinal magnetization, or longitudinal magnetization in two or more directions. Longitudinal magnetization utilizing a coil is frequently used in Air Force NDI laboratories on a variety of test parts. The magnetic field produced will enter and exit the test part perpendicular to the direction the electrical current is passed through the coil. This produces an ideal situation for locating transverse indications. (see Figure 3-1) More precisely, if a bolt were longitudinally magnetized in a coil the critical inspection areas would be under the head and between the threads as well as any transverse defect along the whole length of the bolt. On a tube-shaped part with a flanged end, the critical inspection area would be the radius at the base of the flange and transverse discontinuities along the length of the tube. Longitudinal magnetization SHOULD be performed after circular magnetization if a circular shot is required. Since the magnetic field enters and exits the test part it can be observed by field indicators and therefore any residual field can be removed during demagnetization.
Figure 3-1.
Longitudinal Magnetization in a Coil
3.1.4.1 Cross-Sectional Area. The relationship between the cross-sectional area of the part and the cross-sectional area of the coil will determine whether the part can be inspected within a coil by laying the part in the bottom, or by centering the
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T.O. 33B-1-2 part in the coil, and which formula will be used for estimating the amperage required. The cross-sectional area for the part and coil are determined as follows: A = πr2 Where: A = Cross-sectional Area π = 3.1416 r = radius (1/2 of the diameter) The diameter of the part is the largest distance between any two points on the outside circumference. Example: An 18-inch diameter coil is used to inspect a part having a 2-inch diameter Area of Coil (18” diameter) Area of Part (2” diameter) A = πr2 A = πr2 A = π(9)2 A = π(1)2 A = 254.46 sq. inches A = 3.14 sq. inches 3.1.4.1.1 When the cross-sectional area of the part is less than one-tenth of the cross-sectional area of the coil; the part is magnetized lying in the bottom of the coil. 3.1.4.1.2 When the cross-sectional area of the part is greater than one-tenth of the cross-sectional area of the coil; the part must be magnetized in the center of the coil. 3.1.4.1.3 The diameter of the largest part that can be magnetized lying in the bottom of a coil or placed next to the coil wall for some typical coil sizes is listed in (see Table 3-2). For any given coil diameter, parts with diameters larger than those listed SHALL be magnetized by some other method, such as centering them in the coil, using a cable wrap, or using a larger coil. Table 3-2.
Coil Size vs. Maximum Part Diameter for Bottom of Coil Shot
Coil Diameter (inches) 8 12 15 18 20 24
Maximum Part Diameter (inches) 2.5 3.8 4.7 5.7 6.3 7.6
3.1.4.2 Selecting the Correct Amperage for a Coil Shot. The useful magnetizing field produced from a coil extends approximately 6 to 9-inches to either side of the coil. For longer parts, one or more inspections are required along the length of the part, when repositioning longer parts in the coil allow a 3-inch overlap. The formulas are intended for parts with an L/D ratio (length divided by diameter) between 3 and 15. To inspect parts with an L/D ratio less than 3 consult the Weapons System ALC NDI Manager. For parts with an L/D ratio greater than 15, use 15 as the value for the ratio. 3.1.4.2.1 Formula for Part Lying in Bottom of Coil. The following formula is used when the cross-sectional area of the part is less than one-tenth the cross-sectional area of the coil(s) and is used whenever the part is lying in the bottom of the coil, or is placed next to the coil wall during magnetization. If the part has hollow portions, replace D with Deff (see paragraph 3.1.4.2.2). I = KD NL Where: I = Current through coil (amperes) K = 45,000 (a constant, ampere-turns)
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T.O. 33B-1-2 L = Length of the part (inches) D = Diameter of the part (inches) N = Number of turns in coil Example: Determine the current required to longitudinally magnetize a steel part, 10-inches long with a diameter of 2inches using a 12-inch diameter coil having 5 turns. To determine a cross-sectional area ratio between part and coil, refer to (see paragraph 3.1.4.1). Substituting the known values and doing the calculations gives: I = 45000 x 2 5 x 10 I = 1800 amperes
Table 3-3. Part length in Inches (L) 12 12 16 10 18 14
Typical Current for Five-Turn Coil with Part at the Bottom of Coil
Part Diameter in Inches (D) 3 2 2 1 1 1/2 1
L/D Ratio 4 6 8 10 12 14
Ampere-Turns Required 11,250 7,500 5,625 4,500 3,750 3.214
Amperes Required 2,250 1,500 1,125 900 750 643
3.1.4.2.2 Determining the Effective Diameter. For hollow and cylindrical test parts, the diameter of the test part is substituted with the calculated effective diameter. Calculate the effective diameter as follows:
Example: Determine the effective diameter of a tube-shaped part with an outside diameter equal to 5-inches and an inside diameter of 4.5-inches.
3.1.4.3 Formula for Part in Center of Coil. This formula is used when the cross-sectional area of the part is greater than one-tenth and less than one-half of the cross-sectional area of the coil(s). I = KR N(6(L/D) – 5) Where: I = Current through coil (amperes) K = 43,000 (a constant, ampere-turns) R = Radius of coil (inches) N = Number of turns in coil
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T.O. 33B-1-2 L = Length of part (inches) D = Diameter of the part (inches) The term 6(L/D)-5 is called the effective permeability. Example: Determine the current needed to longitudinally magnetize a 12-inch long part with a diameter of 4-inches and using a 5 turn, 12-inch diameter coil. To determine the cross-sectional area ratio between the part and the coil, refer to (See paragraph 3.1.4.1). If the part contains hollow portions, D should be replaced with Deff (See paragraph 3.1.4.2.2). Substituting known values gives: I = 43000 x 6 5(6(12/4) - 5) I = 3969 amperes 3.1.4.4 Procedure for Inspecting Test Parts in Coil. Ensure the process controls on equipment and material have been performed prior to inspection. Ensure part preparation is completed and is satisfactory for effective magnetic particle inspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-1-1 and AFOSH Standard 91-501 are required in this inspection procedure and SHALL be adhered too. a. Calculate the cross-sectional area of the test part and the coil. From the calculation, determine the position in which the test part will lay in the coil. (See paragraph 3.1.4.1) b. Calculate the required amperage. (See paragraph 3.1.4.2.1 or paragraph 3.1.4.3) c. Clear the magnetic particle unit bench of any obstructions or debris. d. Unlock and roll back the tailstock. Lock the tailstock down when it has cleared the area needed to perform the inspection. e. Unlock and position the coil so that the inspector has easy access to both sides of the coil and has room to position the test part as required. Lock down the coil. f. Set the unit for AC or DC (as required) operation in the coil configuration. Some units will have an Energize Master switch that needs to be pulled out to the ‘‘ON’’ position. g. Place test part in the coil as required. (see Figure 3-1) h. Set amperage at one-half of the calculated value for the test part. (1) Initiate 2 shots in quick succession. (2) Measure the field strength with a Hall-Effect probe gauss meter. Acceptable field strength is 30 to 60G for continuous particle applications and residual applications. (3) Increase amperage by 10% and repeat procedure until an acceptable gauss reading is obtained. (4) If a gauss meter is not available, use the same procedure with a QQI shim affixed to the test part in the area of interest (See paragraph 3.1.9). Use the wet continuous particle application method (spray or flow the suspension over the test part, and then divert the suspension simultaneously or slightly before energizing the magnetic circuit). Inspect the QQI shim under black light illumination. When a bright and defined build-up of magnetic particles is observed, sufficient magnetic field strength is present to perform the inspection. (see paragraph 3.2.1.1)
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T.O. 33B-1-2
NOTE When performing inspections on multiple like items it is not necessary to use the QQI shims or the gauss meter on each individual test part. Once acceptable amperage has been selected, inspect like items at the settings determined by the QQI test. i. Place the test part in the coil. (see Figure 3-1) (1) Perform a wet continuous particle application method (spray or flow the suspension over the test part then divert the suspension simultaneously or slightly before energizing the magnetic circuit). (2) Initiate 2 shots in quick succession. (3) Examine the test part under black light illumination. This technique is most sensitive to transverse flaws. j. Demagnetize the test part. (See paragraph 3.1.7.2) k. Post-clean the test part. (See paragraph 3.1.8) 3.1.5 Longitudinal Magnetism Induced by Portable Yokes. Portable yokes, also known by trade names such as ‘‘Parker Probes’’, provide a reliable induced magnetic field in test parts and are commonly used for inspection outside the shop environment. This equipment is easy to use and adequate when testing small castings or machine parts for surface cracks and weld inspection. They induce a strong magnetic field into that portion of a part that lies between the poles or legs of the yoke. The induced field flows from one leg of the yoke to the other regardless of the style or leg configuration. Since no current is flowing through the part being subjected to inspection, it is impossible to overheat or burn the part. NOTE Magnetize the test part in 2 or more directions or use a circular shot to ensure 100% inspection coverage. 3.1.5.1 Procedure for Inspecting Test Parts with Portable Yoke. Ensure the process controls on equipment and material have been performed prior to inspection. Ensure part preparation is completed and is satisfactory for effective magnetic particle inspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-11 and AFOSH Standard 91-501 are required in this inspection procedure and SHALL be adhered too. a. Place test part on a nonmagnetic surface. b. Set the portable yoke for AC or DC (as required) operation and turn the field intensity thumb dial to full power. c. Place the leg ends of the yoke on the part so that the intended inspection area lies between the leg poles. Energize the yoke for five (5) full seconds. d. Use a field indicator to check for a residual field. If a half scale deflection is obtained the test part can be effectively inspected with magnetic particle procedures. e. If the field indicator does not show the presence of a strong residual field place a QQI shim in the area of interest and perform a wet continuous particle application with the yoke energized at full power. (see paragraph 3.2.1.1) (1) Observe the QQI shim under black light illumination. If a bright well-defined indication appears, the test part can be inspected with the wet continuous method. (2) If an indication does not appear, some other NDI method will be more appropriate for the test part. NOTE When performing inspections on multiple like items it is not necessary to use the QQI shims or gauss meter on each individual test part. Once acceptable amperage has been selected, inspect like items at the settings determined by the QQI test. f. Place the leg ends of the yoke on the part so that the intended inspection area lies between the leg poles.
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T.O. 33B-1-2 g. Perform a wet continuous particle application with the yoke energized at full power. h. Inspect the area under black light illumination. Note any defects present. (1) Look for evidence of magnetic saturation. (2) If the test part displays signs of magnetic saturation, demagnetize the part, turn the field intensity thumb dial counter clockwise one-quarter turn and inspect again. i. Turn the portable yoke 90 degrees, place the leg ends on the part and perform the application and inspection procedure again. j. Repeat the procedure until 100% of the inspection area is completed. k. Demagnetize the test part as required. (See paragraph 3.1.7) l. Post-clean the test part. (See paragraph 3.1.8)
Figure 3-2.
Magnetic Field Produced by a Portable Yoke
3.1.6 Circular Magnetism Produced by Direct Contact. Circular magnetization is used for the detection of radial discontinuities around edges of holes or openings in parts. It is also used for the detection of longitudinal discontinuities, which lie in the same direction as the current flow. This technique produces circular magnetization by passing electric current through the part itself (see Figure 3-3). Direct contact is applied to parts by placing them directly between the headstock and tail stock. Lead faceplates and copper braid pads SHALL be used to prevent arcing, overheating, and splatter. Electrical contact SHALL be as good as practicable to minimize over heating or arcing. Excessive heating at the contact points may negatively affect the serviceability of the test part (e.g., burn the part; affect its temper, finish, etc.).
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T.O. 33B-1-2
Figure 3-3.
Circular Magnetic Field Produced by Direct Contact
3.1.6.1 Direct Contact Method Amperage Calculation. Amperage selection for the direct contact method is simple and straight forward, 300 to 800 amperes per inch of diameter. Generally, the lower (300 to 500 amperes) values produce adequate field strength for most applications. 3.1.6.1.1 Procedure for Direct Contact Circular Magnetization. Ensure the process controls on equipment and material have been performed prior to inspection. Ensure part preparation is completed and is satisfactory for effective magnetic particle inspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-1-1 and AFOSH Standard 91-501 are required for this inspection procedure and SHALL be adhered too. CAUTION Precautions SHALL be taken to ensure that the electric current is not flowing while contacts are being applied or removed and that excessive heating does not occur in the contact area. Prods are not authorized on aerospace components and portable clamps SHALL only be used on aerospace components with direction and approval of the appropriate ALC NDI Manager. a. Measure the diameter of the test part. Determine the amperage required to perform the inspection. Start with the lowest setting possible for a given test part. b. Clear the magnetic particle unit’s bench area of any obstruction or debris. c. Place a central bar conductor (CBC) between the headstock and tailstock. Lock down the tailstock. d. Pour or spray the bath vehicle where the bar and contact pads meet. (Completely saturating the area is not necessary.) e. Fully depress the foot switch to clamp the part firmly in place. f. Set unit for AC or DC (as required) operation in the contact mode. Some units will have an Energize Master switch that needs to be pulled out to the ‘‘ON’’ position. g. Set the amperage potentiometer to the approximate setting required for the test part. h. Initiate the contact shot. Note the amperage indicated on the ammeter. Adjust the potentiometer to achieve the required output. i. Initiate the contact shot again and verify the amperage indicated on the ammeter meets the setting requirements. j. Fully depress the foot switch to release the CBC, and then remove the CBC.
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T.O. 33B-1-2 k. Place the part to be inspected between stocks. Adjust the tailstocks to accommodate the test part. Lock down the tailstock. l. Pour or spray the bath vehicle where the part and contact pads meet. (Completely saturating the area is not necessary.) m. Fully depress the foot switch to clamp the part firmly in place. n. Check the equipment setting to ensure correct configuration. o. Place a QQI shim in the area of interest. (see paragraph 3.2.1.1) p. Perform the wet continuous method of particle application. Spray or flow the suspension over the test part then divert the suspension simultaneously or slightly before energizing the magnetic circuit. Initiate 2 shots in quick succession. q. Inspect the QQI shim under black light illumination. When a bright and defined build-up of magnetic particles is observed, sufficient magnetic field strength is present to perform the inspection. r. Increase the amperage until a good indication is formed on the QQI. NOTE When performing inspections on multiple like items it is not necessary to use the QQI shims or gauss meter on each individual test part. Once acceptable amperage has been selected, inspect like items at the settings determined by the QQI test. s. Perform the inspection with the equipment configuration and amperage derived from this procedure. t. Demagnetize the test part as required. (See paragraph 3.1.7) u. Post-clean the test part. (See paragraph 3.1.8) 3.1.6.2 Circular Magnetism Using a Central Bar Conductor (CBC). Circular magnetism induced with a CBC is an excellent procedure to inspect the inside diameter of ring-shaped or cylindrical test parts. The effective field strength decreases the further from the CBC it extends. If the outside surface of the test part must be inspected and the direct contact method cannot be used, a CBC shot with DC will provide the most effective inspection using stationary equipment. AC is the preferred current for inspecting the inside surface of ring-shaped or cylindrical test parts. Circular magnetism is sensitive to longitudinal cracks as shown in (see Figure 3-4 and Figure 3-5) and is effective for inspecting radial cracks emitted for holes or other openings in the test part.
Figure 3-4.
Circular Magnetism Using a CBC
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T.O. 33B-1-2
Figure 3-5.
Circular Magnetism Using a CBC on Ring-Shaped Parts
3.1.6.2.1 Central Bar Conductor Method Amperage Calculation. The rule of thumb for a CBC shot varies from 100 to 1000 amperes per inch of diameter. For the purpose of this inspection procedure, we will use the same value as the direct contact method, 300 to 800 amperes per inch of diameter. When the CBC is passed through a ring-shaped or cylindrical part and is placed against an inside wall of the part (offset central conductor), the diameter for amperage calculation is the sum of the diameter of the CBC plus twice the wall thickness. Example: Inspect a 6-inch tube with a one-inch CBC, the wall thickness is 0.25-inch. [1 + (0.25 + 0.25)] = 1 + 0.5 = 1.5-inches of diameter 3.1.6.2.2 Effective Region of Inspection. The effective region of inspection when using an offset central bar conductor is equal to 4 times the diameter of the bar conductor. Effectively, a 1-inch CBC will yield a 4-inch inspection area; 2-inches on either side of the center of the CBC. 3.1.6.2.3 Procedure for Circular Magnetization using a CBC. Ensure the process controls on equipment and material have been performed prior to inspection. Ensure part preparation is completed and is satisfactory for effective magnetic particle inspection. All relevant safety equipment and procedures directed by Chapter 3 Section VIII of T.O. 33B-1-1 and AFOSH Standard 91-501 are required for this inspection procedure and SHALL be adhered to. CAUTION Precautions SHALL be taken to ensure that the electric current is not flowing while contacts are being applied or removed and that excessive heating does not occur in the contact area. a. Calculate the diameter of the test part. Determine the amperage required to perform the inspection. Start with the lowest setting possible for a given test part. b. Clear the magnetic particle unit’s bench area of obstructions or other debris. c. Place a central bar conductor between the headstock and tailstock. Lock down the tailstock. d. Pour or spray the bath vehicle where the bar and contact pads meet. (Completely saturating the area is not necessary.) e. Fully depress the foot switch to clamp the CBC firmly in place. f. Set unit for AC or DC (as required) operation in the contact mode. Some units will have an Energize Master switch that needs to be pulled out to the ‘‘ON’’ position. g. Set the amperage potentiometer to the approximate setting required for the test part.
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T.O. 33B-1-2 h. Initiate the shot. Note the amperage indicated on the ammeter. Adjust the potentiometer to achieve the required output. i. Initiate the shot again and verify the amperage indicated on the ammeter meets the setting requirements. j. Fully depress the foot switch to release the CBC, and then remove the CBC. k. Place the CBC through the part to be inspected and insert the CBC into the stocks. Adjust the tailstocks to accommodate the test part and CBC. Lock down the tailstock. l. Pour or spray the bath vehicle where the CBC and contact pads meet. (Completely saturating the area is not necessary.) m. Fully depress the foot switch to clamp the CBC firmly in place. n. Check the equipment setting to ensure correct configuration. o. Place a QQI shim in the area of interest. (see paragraph 3.2.1.1) p. Perform the wet continuous method of particle application. Spray or flow the suspension over the test part then divert the suspension simultaneously or slightly before energizing the magnetic circuit. Initiate 2 shots in quick succession. q. Inspect the QQI shim under black light illumination. When a bright and defined build-up of magnetic particles is observed, sufficient magnetic field strength is present to perform the inspection. r. Increase the amperage until a good indication is formed on the QQI. NOTE When performing inspections on multiple like items it is not necessary to use the QQI shims or the gauss meter on each individual test part. Once acceptable amperage has been selected, inspect like items at the settings determined by the QQI test. s. Perform the inspection with the equipment configuration and amperage derived from this procedure. t. Demagnetize the test part as required. (See paragraph 3.1.7) u. Post-clean the test part. (See paragraph 3.1.8) 3.1.7 Demagnetizing Test Parts. Unless a specific instruction states demagnetization is not required, all aircraft test parts SHALL be demagnetized. All other test parts SHOULD be demagnetized each time the inspection procedure is performed. NOTE It is recommended that all parts circularly magnetized be magnetized longitudinally at the same or higher amperage prior to demagnetization. 3.1.7.1 Demagnetization on Stationary Equipment Using AC. a. Select AC, Coil, and Demag operation on the unit’s selector switches. b. Turn the current control clockwise to 3/4 of scale or 10% greater than the magnetizing current used on the test part. c. Initiate shot. During the AC Demag cycle the current is ramped down to zero in approximately 5 to 10 seconds. d. Using a field indicator measure the ends of the test part. Residual field SHALL be two (2) increments or less on field indicators or three (3) gauss or less using a hall-effect gauss meter. 3.1.7.2 Demagnetization on Stationary Equipment Using DC. a. Select DC, Coil, and Demag operation on the unit’s selector switches.
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T.O. 33B-1-2 b. Turn the current control clockwise to 3/4 of scale or 10% greater than the magnetizing current used on the test part. c. Initiate shot. Output current will pulse at reversing polarities and decay to zero during it’s approximately 25 to 30 second cycle. d. Using a field indicator measure the ends of the test part. Residual field SHALL be two (2) increments or less on field indicators or three (3) gauss or less using a hall-effect gauss meter. 3.1.7.3 Demagnetization Using Portable Yokes. Portable yokes present some unique problems, if the part comes in contact with both legs of the yoke in the same general configuration as the magnetizing shot, the part can be magnetized again. AC is recommended for most demagnetization operations because the nature of alternating currents’ reversing current flow will aid in the demagnetization of a test part. a. Open the legs of the yoke so the test part can pass through it. b. Hold the test part 1-foot from the yoke. c. Slowly pass the part through the yoke legs and 3 to 5 feet beyond while the yoke is energized. d. Turn the test part 90° and repeat the procedure. e. If the test part is too large to handle in this way, follow the same basic procedures moving and rotating the yoke instead of the test part. f. Using a field indicator, measure the ends of the test part. Residual field SHALL be two (2) increments or less on field indicators or three (3) gauss or less using a hall-effect gauss meter. 3.1.8 Post-Cleaning Test Parts After Magnetic Particle Inspection. After the demagnetization operation has been accomplished, dip the test part in clean vehicle that does not contain magnetic particles. Check the test part under black light illumination for fluorescence. Wipe down the test part with a clean cloth or paper towel dampened with an approved solvent. Dry with lowpressure shop air. After portable inspections, wipe the test part down with a clean dry cloth or paper towel. Perform a final wipe down with a clean cloth or paper towel dampened with an approved solvent. Check the test part under black light illumination for excessive fluorescence. 3.1.9 QQI Shims. The QQI is a small, thin, metal shim, made of low carbon steel that contains artificial defects for establishing or verifying MPI techniques. The artificial flaw is etched or machined on one side of the foil to various depths but usually 30% of the foil thickness. In use, the shims are firmly attached to the test part surface with the flawed side down against the test part in the area of interest. Tape is most commonly used and is placed on all four sides of the shim to prevent magnetic particle vehicle from seeping under the shim. The QQI SHOULD only be used with the wet continuous method of particle application.
Figure 3-6.
Quantitative Quality Indicators (QQI)
3.1.10 Magnetic Particle Inspection Interpretation. Magnetic Particle interpretation is done under black light in an inspection booth or darkened area. Portable inspections may require a locally manufactured or purchased tent-like apparatus made of dark cloth or canvas to reduce ambient light levels and enhance inspection sensitivity. Identify indications as linear or rounded and measure the largest dimension of the indication for comparison to acceptance criteria. A rounded indication has length that is less than 3 times its width. A linear indication has a length 3 or more times its width. Evaluate indications according to limits in technical data. If technical data is not specific or no technical data is available, consider all linear indications relevant and rounded indications 1/16th of an inch or larger relevant for both aircraft and nonaircraft test parts.
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T.O. 33B-1-2 3.1.10.1 Defects will generally be linear or aligned porosity type indications resulting from: • • • •
Fatigue cracks. Stress corrosion cracks. Intergranular corrosion. Weld defects.
3.1.10.2 Non-relevant indications will not be marked. Non-relevant indications are generally: • • • •
Scratches. Nicks. Tool marks. Machined marks.
3.1.10.3 Defects should be marked on the part surface with an approved marking pencil. Measure the defect and note identifying characteristics. Describe the defect in detail including its location and orientation. Then document inspection findings IAW Air Force Instructions and local directives. An example of a good defect description is as follows: ‘‘Magnetic particle inspection of welds on transfer case part number 128-6380. Crack noted and marked on the inlet to case weld. The indication is sharp, well defined, bright, and linear. The defect is 2.125 inches long and runs down the center of the weld crown.’’ NOTE Air Force NDI personnel SHALL NOT make serviceability determinations except as described in AFI 21-101 (field units only). The role of the NDI inspector is normally limited to providing a detailed description of the defect and its location. Disposition and repair responsibility for a flawed part or airframe lies with Structural Maintenance personnel or the owning workcenter and the appropriate engineering authority.
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T.O. 33B-1-2
SECTION II FLUORESCENT MAGNETIC PARTICLE PROCESS CONTROL PROCEDURES 3.2
SYSTEM EFFECTIVENESS CHECK (KETOS RING). NOTE The prior to use or daily requirement for black light UV intensity check and particle concentration/suspension settling tests SHALL be performed and within limits prior to performing the system effectiveness check.
The Ketos ring has been the standard tool used by the Air Force to evaluate system effectiveness for some years now. While it is a useful tool, it has definite limitations. To realize the greatest sensitivity to change in the bath material, baseline the KETOS ring and the magnetic particle unit by recording the actual readings at each checkpoint in the test when the bath is new. Compare subsequent test reading to the baseline to observe small changes immediately. Conduct the system effectiveness check as follows: a. Check for residual magnetism by applying the magnetic particle bath, then wait 60-seconds for any indications to form. If any indications are present on the outer edge, the ring SHALL be demagnetized and the check repeated until no indications are formed. b. Place a one-inch central bar conductor (CBC) between the stocks and initiate the air cylinder to clamp the CBC into place. Set unit for AC operation in the contact mode. Adjust the current control until 1000 amps is displayed on the readout. c. Remove the CBC from the stocks and slide the Ketos ring onto the bar. Clamp the CBC into the stocks. Perform the wet continuous method of particle application at 1000 amperes (see Table 3-4). Wait 60-seconds for any indications to form on the outer edge of the Ketos ring. An indication should form above the first hole (see Figure 3-7). d. Remove the CBC from the stocks and slide the Ketos ring off the bar. Place the CBC back into the stocks and initiate the air cylinder to clamp it down. e. Set the magnetic particle unit to DC operation in the contact mode. Adjust the current control until 1400 amperes is displayed on the readout. f. Remove the CBC from the stocks and slide the Ketos ring onto the bar. Clamp the CBC into the stocks. Perform the wet continuous method of particle application at 1400 amperes (see Table 3-4). Wait 60-seconds for any indications to form on the outer edge of the Ketos ring. An indication should form above the third hole (see Figure 3-7). g. Repeat step d, step e, and step f at 2500 and 3400 amperes, indications should appear above holes five and six (see Figure 3-5). Lack of indications at the proper holes may indicate a malfunctioning magnetic particle unit, a low particle concentration, or a Ketos ring not in the annealed condition. The cause of the malfunction SHALL be determined with additional process checks (e.g., amp indicator, concentration, etc,) and corrected prior to performing additional magnetic particle inspections with the deficient system. NOTE Ketos rings that are plated or corroded SHALL NOT be used. Corrosion and plating can cause false readings.
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Figure 3-7.
Table 3-4. Type of Suspension Non-fluorescent
Dry Powder
Fluorescent
Non-fluorescent Dry Powder Fluorescent
Ketos Ring
Ring Specimen Indications
D.C. Amperage 1400 2500 3400 1400 2500 3400 1400 2500 3400 A.C. Amperage 1000 1000 1000
Minimum No. of Holes Indicated 3 5 6 4 6 7 3 5 6 1 1 1
3.2.1 Quantitative Quality Indicators (QQI). Test specimen(s) used with QQIs offer a more versatile means of checking system performance than afforded by the Ketos ring. The specimens can be real parts or designed to be representative of the most challenging inspection to be currently performed. This combination is capable of providing an adequate check on any magnetic particle inspection system. Poor indications may require further process control evaluations to be performed (e.g., amp indicator check, concentration check, etc.). Even though QQIs respond to the applied, not residual field, demagnetization is necessary of the specimen(s) in order to remove the previously applied inspection media.
3-15
T.O. 33B-1-2 3.2.1.1 Using the QQI. CAUTION Exercise care when using QQIs on curved surfaces. Excessive bending will damage a QQI. Usually the thinner QQI will be used on curved surfaces; however they are fragile. The thicker QQI is less fragile, but can still be damaged by excessive bending. NOTE Use of a QQI will require a second magnetic particle inspection (without the QQI) if the QQI is placed in an area where a crack may be present. Thoroughly clean and dry the area where the QQI is placed. Use cleaning solvent, IAW MIL-C- 38736. Place the appropriate QQI in place with the slot side against the surface of the part and one axial groove parallel to the current direction. If the test part has a very specific area of interest, place the QQI in this area. If the test part is a 100% coverage inspection, place the QQI in the least favorable inspectable location on the test part for that particular shot. In general, the 30-percent deep slot is adequate for most defects. Critical inspections may require the 15- percent deep slot; and rough castings or weldments may require the 60-percent deep slot. Use transparent adhesive tape (e.g., Scotch brand 191, 471, or 600 series) to hold the QQI in place. Apply the tape to all four edges to ensure good contact (with no air gap) and to prevent particles from getting under the QQI. The tape SHALL NOT cover the area of the QQI where the indications will form. Super glue may be used to provide a fixed bond. Super glue can be removed by soaking in acetone. Conduct the inspection and observe the results under the appropriate lighting. 3.2.2 Cracked Parts. If available, the ultimate specimens for the performance tests are cracked parts. Poor indications may require further process control evaluations to be performed (e.g., amp indicator check, concentration check, etc.). These require careful handling to remain corrosion-free and retain their flaw size. 3.2.3 Amperage Indicator Check. Perform amperage indicator accuracy checks using a calibrated ammeter/shunt authorized in AS-455. Authorization for any other ammeter/shunt SHALL be approved by the AF NDI Office. Operate the ammeter/shunt in accordance with the commercial manufacturer’s operating instruction. DC amperage variations exceeding ±10% of read-out value or ±60 amperes, whichever is greater, requires trouble shooting and maintenance action. AC amperage variations exceeding ±10% requires trouble shooting and maintenance action. Perform the amperage indicator check on the range that is expected to be used. As a minimum, the amperage range used in the KETOS ring check SHALL be tested. 3.2.4 Quick Break Test. The quick break test is accomplished to ensure an accurate decay rate, which is sufficient for quick break magnetization. A quick break tester is authorized in AS-455. Operate the quick break tester in accordance with the commercial manufacturer’s operating instructions. Failure of the quick break test requires trouble shooting and maintenance action. The quick break test SHALL be performed at intervals stated in (see Table 1-1). 3.2.4.1 Generic Quick Break Test Instructions. In the absence of a commercial manufacturer’s instruction, the following procedure will be sufficient for the Magnaflux Quick Break Tester, Part Number 148335 or equivalent: a. Clear the horizontal wet bench unit of all ferrous parts, rags, or other obstructions. b. Retract the tailstock and lock it down so the operator has an unobstructed access to the coil. c. Move the coil 12 to 18 inches from the headstock and lock it down. d. Remove the copper bus bar and bracket from the quick break tester. Center the tester on the bottom surface of the inside diameter of the coil. The tester should be placed perpendicular to the coils with the studs facing up. If the studs are facing up and the indicating lamp is facing the tail stocks, the tester is in the correct position. e. Set magnetic particle unit for DC operations at 2000 amperes in the coil mode. f. Initiate the coil shot and observe the indicating lamp as the shot terminates. A flash of the lamp indicates a good ‘‘quick-break.’’ Sometimes a flash may occur at the beginning and end of the shot; this is acceptable. The absence of a flash indicates a malfunction in the circuitry of the magnetic particle unit.
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T.O. 33B-1-2 3.2.5 Dead Weight Check. The dead weight check is conducted on portable electromagnetic yokes (e.g., Parker Probes). Repair or replace equipment that fails the dead weight check. Perform the process control check as follows: 3.2.5.1 Locally manufacture test weights from SAE 4130 or 4340 steel. A 10-pound weight is required for AC operation, either a 30- or 50-pound weight is required for DC operation. (For more information on the manufacture of test weights, see T.O. 33B-1-1) a. Place the 10-pound weight on the floor. Set the portable magnetic particle unit to AC operation. Extend the legs straight out and space the legs from three to six inches. Place the leg ends on the test weight and energize the unit. Lift the test weight off the ground. A portable magnetic particle unit must be able to hold suspended the ten-pound test weight. b. Place the 30-pound weight on the floor. Set the portable magnetic particle unit to DC operation. Extend the legs straight out and space the legs from two to four inches. Place the leg ends on the test weight and energize the unit. Lift the test weight off the ground. A portable magnetic particle unit must be able to hold suspended the 30-pound test weight. A 50-pound test weight and a four to six inch leg spread may also be used.
Figure 3-8.
Black Light Intensity
3.2.6 UV-A Black Light Intensity and Ambient Light Requirements. CAUTION When performing portable fluorescent magnetic particle inspection, a dark colored canvas or photographers black cloth SHALL be used to darken the area during the examination. A portable fluorescent magnetic particle inspection SHALL NOT be performed in ambient conditions, lighting conditions above 20 foot-candles. Black lights SHALL be directed away from the eyes and gloves SHALL be worn to protect the skin from exposure to ultraviolet light. Any glove approved for use in magnetic particle or liquid penetrant inspections will provide adequate protection to the skin from ultraviolet light. Ultraviolet light filtering safety eyewear SHALL be used to prevent potential detrimental health effects. Black lights SHALL be tested with an approved and calibrated UV-A digital radiometer at intervals required in (Table 1-1). The intensity SHALL be at least 1000-micro-watts per square centimeter (µW/cm2) measured at a distance of 15 inches from the face of the black light filter lens. The UV-A digital radiometer is calibrated in accordance with T.O. 33K-1-100-CD-1. 3.2.6.1 Excessive Ambient White Light. There are two white light tests that must be performed to maintain a good inspection system, each individual black light is tested for white light output and a collective test is performed for inspection 3-17
T.O. 33B-1-2 booths. The inspection booth test measures ambient white light from all sources including white light emitted from black lights and reflected white light from areas adjacent to the inspection booth. The individual black light test measures white light emitted directly from the black light. The white light tests are performed with an approved and calibrated photometer at intervals directed in (see Table 1-1). The white light photometer is calibrated in accordance with TO 33K-1-100-CD-1. For stationary inspections (laboratory inspection booths), the ambient white light SHALL NOT exceed 2 foot-candles. The individual black light test is accomplished in a fully darkened booth with the tested black light on and all others off. The check is similar to the UV-A test with the sensor 15-inches from the black light filter lens. The collective test is performed in the inspection booth with all black lights normally used in the booth turned on. The photometer sensor is placed in the area where parts are normally inspected. The acceptance criteria for both tests are the same; no more than 2 foot-candles of white light is allowed. For portable inspections, where ambient light conditions cannot be controlled below 2 foot-candles, higher UV-A intensities at the inspection surfaces are required. The minimum UV-A intensity under varying ambient light levels (see Table 3-5). Values of 3,000 µW/cm2 can be achieved with acceptable black light sources by moving the source closer than 15-inches to the part, yet leaving sufficient space to observe the specific area of interest. Table 3-5.
Empirical Black Light Intensity Requirements at Various Ambient Light Levels for Portable Inspections
Ambient Light in Foot-Candles 0.01 to 2 2 to 10 10 to 20
Inspection Conditions Fully darkened inspection booth Dark-to-dim interiors such as warehouses or storage areas Dim interiors
Minimum UV-A Intensity at Inspection Surface µW/cm2 1000 3000 5000
3.2.7 Fluorescent Background Check for New Bulk Suspension. A fluorescent background check SHALL be accomplished on vehicle material used in the fluorescent magnetic particle inspection method if conformance to DOD-F87935 is in question. One procedure for checking the background is as follows: a. Obtain a clean glass tube of sufficient length to reach from the middle of the bulk vehicle container to at least 6inches above the container opening when it is in the vertical position. b. Insert the tube slowly into the bulk vehicle. c. Place thumb over protruding end of the glass tube and remove the tube from the container. d. Illuminate vehicle in the glass tube with a black light in a darkened area. e. If vehicle does not fluoresce, proceed with its use. If the vehicle fluoresces, determine the fluorescence in accordance with the appropriate section of DOD-F-87935. Dispose of vehicle not conforming to DOD-F-87935. 3.2.8 Particle Concentration Test. NOTE Prior to adding the magnetic particles to the vehicle, the particles SHALL be demagnetized to eliminate any clumping that may have developed during storage due to magnetization. The following procedure is used to determine the concentration of magnetic particles and to check for the accumulation of dirt or other contaminants in a suspension. The equipment required is a 100-cubic centimeters (cc) or 100-milliliters (ml) pear-shaped, graduated centrifuge tube and nonferrous stand (see Figure 3-9). The difference between milliliters (ml) and cubic centimeters (cc) in this case is negligible, and the two terms are used interchangeably for this paragraph.
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T.O. 33B-1-2
Figure 3-9.
Centrifuge Tube
a. Thoroughly agitate the suspension. b. Run suspension through the hose and nozzle for at least 1-minute. This is to ensure the suspension in the hose is fresh and agitated. c. Fill the 100 cc (100 ml) centrifuge tube with agitated suspension using the hose. d. Demagnetize the suspension in the tube to reduce clumping. e. Place the centrifuge tube in its non-ferromagnetic stand, and allow the suspension to set on a vibration free surface for: • •
1-hour for oil baths, OR 30-minutes for water baths.
f. Observe the total level (concentration) of settled particles at the end of the settling period. The level of contaminants is subtracted from the total concentration to obtain the current concentration of particles. NOTE Besides the magnetic particles, dirt in the bath will also settle out and usually show as a separate layer on top of the particles. The layer of dirt and lint is usually easily distinguishable, since it is of a different color and texture from the particles. Also easily distinguishable are iron peening shot and blasting grit; both will settle faster and lie beneath the magnetic particles. g. If the concentration of magnetic particles is above or below the range required, correct by adding vehicle or magnetic particle powder respectively. Visible magnetic particle bath concentrations SHALL be: 1.2 to 2.4 milliliters (ml) of particles per 100 ml of vehicle. The optimum range is 1.5 to 2.0 ml/100 ml. Fluorescent magnetic particle bath
3-19
T.O. 33B-1-2 concentrations SHALL be: 0.1 to 0.4 ml of particles per 100 ml of vehicle. The optimum range is 0.15 to 0.20 ml/100 ml. Repeat step a through step f of the settling test after making corrections. h. Return contents of centrifuge tube to the in-use bath, and clean the tube prior to next test. NOTE Part processing and/or process control inspections SHALL NOT be accomplished prior to the full 1-hour (or 30minute) time limit passing and the bath has been approved for daily use. The suspension concentration SHALL be within T.O. limits prior to use. 3.2.9 Vehicle Fluorescence Check. The settling test (see paragraph 3.2.8) for particle concentration can also be used to judge vehicle fluorescence and is readily performed at a stationary unit. It is not as accurate as the laboratory test but is reasonably quantitative and reproducible. It can be easily standardized with the material in use, and is quite satisfactory as a daily guide for the inspector. The following procedure is used to perform the vehicle fluorescence check after the steps in the settling test are completed. a. Illuminate the suspension in the centrifuge tube with black light in a darkened area. Only the particle layer will fluoresce. Dirt, lint, etc. will usually settle more slowly than the particles and may be seen as a non-fluorescent band or strip toward the top of the particle layer. For particle concentration (see paragraph 3.2.8) determination, this layer of dirt SHALL be carefully excluded from the total volume read. Dirt accumulation that exceeds 30-percent of the total volume of the particle requires replacement of the bath. b. Fluorescence in the liquid may indicate bath breakdown (fluorescent pigmentation being stripped from the magnetic particles or fine magnetic particles remaining suspended in the vehicle). If the vehicle fluoresces excessively, place the centrifuge tube in its stand with a horseshoe magnet in contact with the centrifuge tube and let sit on a vibration free surface for 1-hour for oil baths and 30-minutes for water baths. Illuminate the vehicle in the centrifuge tube with black light in a darkened area. If the vehicle’s fluorescence is reduced or eliminated, the cause of the fluorescence is fine magnetic particles remaining suspended. If the level of fluorescence remains at the same level, the fluorescent pigmentation has been stripped from the magnetic particles and the bath requires replacement. c. If it is determined the cause of the excessive suspension fluorescence is fine magnetic particles remaining in the vehicle, and they interfere with the results of the system effectiveness check (see paragraph 3.2); attempt to remove them from the holding tank’s magnetic particle bath. This can be done with magnets. Allow the magnetic particle bath in the holding tank to settle (not agitated) for 40-minutes. Place the magnets in the magnetic particle bath, taking care not to place them so deep they will attract the particles that have settled out of suspension. The length of time or number of times that the magnets will have to be cleaned of particles and submerged is dependent upon the seriousness of the problem. The bath SHALL be able to pass the system effectiveness check (see paragraph 3.2), after the removal of as many suspended particles as possible or be replaced. d. If a magnet was used to remove fine magnetic particles from suspension in the centrifuge tube, the suspension SHALL be demagnetized prior to being poured back into the magnetic particle machine. e. Clean the inside of the centrifuge tube to eliminate residual fluorescence remaining after each use. 3.2.10 Acidity Test. The acidity of a water bath SHALL be checked weekly (water baths only). The pH of the water bath SHALL be between 6 and 10. If the parts being inspected have a residual solvent film, more wetting agent is required so the parts’ surface will be completely wetted. Breaking of the bath into rivulets as it is applied over a part is an indication an additional wetting agent is required or the part requires further cleaning. 3.2.11 Water Break Test. Conduct a water break test daily (water baths only) using a clean specimen or part having the smoothest surface finish to be inspected. Flood the specimen with bath and examined once flooding has stopped. If a smooth continuous film of bath forms over the entire surface, sufficient wetting agent is present. Reference SHALL be made to the manufacturer’s recommendations for the correct quantity of wetting agent to be added. 3.2.12 Field Indicator Check. Performance requires a bar magnet or magnet with a north and south pole. Hold the in-use field indicator next to one end of the magnet; a full-scale deflection in one direction should be observed. Move the indicator away from the magnet and note the return to ‘‘0’’ or centerline. Hold the indicator next to the opposite end of the bar magnet, note a full-scale deflection in the opposite end of the scale. Move the indicator away from the magnet and note the return to zero. If proper deflections are observed, then field indicator is serviceable.
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T.O. 33B-1-2
CHAPTER 4 EDDY CURRENT INSPECTION SECTION I EDDY CURRENT INSPECTION GENERAL PROCEDURE 4.1
EDDY CURRENT GENERAL PROCEDURE.
The following eddy current general practice is to be used in conjunction with part specific eddy current procedures or when part specific eddy current procedures do not exist. Section 4.1 defines the approved equipment and standards. Section 4.2 provides guidance on scanning methods for general manual surface eddy current inspection including lift-off compensation when inspection components with nonconductive coatings applied. Section 4.3 provides detailed procedures for performing surface and bolt hole inspection of ferromagnetic, weakly ferromagnetic and non ferromagnetic materials. Part specific procedures SHALL take precedence over this general practice. For eddy current general theory refer to T.O. 33B-1-1. 4.1.1 Approved Equipment. 4.1.1.1 Eddy current instrument: Staveley Nortec 2000D, NSN 6635-01-455-9520 or equivalent. 4.1.1.2 Probe: Probe specifications SHALL be identified in the part specific procedure where a specific procedures exists. Probe substitutions will be necessary for conversion from legacy equipment (e.g., ED-520, HT-100) to the Nortec 2000D series. The following specifications are mandatory for all probe substitutions: • • • • • •
• •
Connectivity: Substitute probes shall connect directly to the Nortec 2000D without use of any adapter (e.g. P/N 9522106.02). The Nortec 2000D probe cable connector is a type, 16-pin Lemo. Frequency: Substitute probes shall operate within the frequency range specified in the existing procedure or generic frequency Table 4-3 when specific procedures are inadequate or do not exist. Coil Shielding: Manual surface probes and automated bolt hole probes shall be shielded unless otherwise specified. Coil/Probe Size: Substitute probe coil/probe diameter shall be equal to the diameter specified in the existing procedure or 1/8th-inch for general surface inspection where specific procedures are inadequate or do not exist. Configuration (length, drop, etc.): As directed by existing procedure or engineering directive. If no guidance is available it is the Inspectors’ choice but must be sufficient to effectively complete the required inspection. Coil Types for Surface Inspection: Unless otherwise specified by the existing procedure, an absolute/bridge or absolute/reflection coil type arrangement is recommended. It is preferred that the reference coil be contained within the probe housing. However, a 16- pin lemo cable that contains the reference coil will allow for use of absolute legacy type probes and is authorized if all other procedural requirements are met. Use of a cable manufactured by the probe manufacturer is preferred in order to achieve optimum coil impedance matching. Automated Fastener Hole Inspection: The probes shall be shielded, differential/reflection. Approved Scanners: Nortec Spitfire, Minimite, and RA/19 NOTE Each probe manufacturer may have their own definitions of probe coil arrangements. Inpectors unsure of the coil/probe required in this procedure, consult with the manufacturer and/or ALC-NDI Engineering.
4.1.1.3 Standard: Unless otherwise identified in the part specific procedure, the Aluminum Air Force General Purpose Eddy Current Standard, NSN 6635-01-092-5129 SHALL be used when inspecting aluminum parts. The Navy General Purpose Eddy Current Standard meets all requirements and is acceptable for use when ever the Air Force Standard is called out. New orders against NSN 6635-01-092-5129 will be filled with the Navy Standard. For inspection of other materials, use the Air Force or Navy General Purpose Eddy Current Standard configuration made of the same part material or use the alloys defined in Table 4-1. For surface eddy current inspection, an acceptable alternate reference standard configuration is shown in (see Figure 4-2).
4-1
T.O. 33B-1-2
Table 4-1. Part Material All Magnetic Steel Alloys Aluminum Inconel Alloys Stainless Steel Titanium
Reference Standard Materials Standard 4340 Steel 7075-T6 Inconel 718 PH13-8MO Ti-6AL-4V
4.1.1.4 Teflon tape: It is required that teflon tape be applied to the contact surface of the probes to protect the probe tip from excessive wear and damage and to reduce probe noise. P/N 3M 5480 or equivalent, maximum thickness 0.005”.
4-2
T.O. 33B-1-2
Figure 4-1.
Eddy Current Reference Standard (Sheet 1 of 2)
4-3
T.O. 33B-1-2
Figure 4-1.
4-4
Eddy Current Reference Standard (Sheet 2)
T.O. 33B-1-2
Figure 4-2.
Alternate Surface Eddy Current Reference Standard
4.1.2 Eddy Current Scanning Techniques. Eddy current inspection procedures throughout this manual contain instructions that are specifically defined in the following paragraphs. 4.1.2.1 Manual Surface Inspection. 4.1.2.1.1 Coating Lift-off Compensation. For inspections performed over painted surfaces, liftoff caused by the paint thickness affects sensitivity and requires compensation during instrument standardization. To compensate for the increased lift-off the appropriate thickness of nonconductive material (plastic shims, paper, etc.) SHALL be placed between the probe and standard during the standardization process unless otherwise specified by the part specific procedure. Determine the appropriate thickness of non-conductive shim by either using a dedicated non-conductive coating thickness gauge or using the procedure as follows: WARNING Coating thickness on the inspection surface greater than 0.010 inch (10 mils) thick will significantly reduce inspection sensitivity and can result in failure to detect cracks. a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows: (1) Select the SETUP MENU. (2) Select DEFAULT and press ENTER. (3) Select LD DEFLT and press ENTER. (4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER. b. Adjust the instrument settings to those defined in (Table 4-2). c. Place the probe onto the surface to be inspected and NULL the instrument. Hold probe still until nulling is complete. The flying-dot should be located at 50% vertical and 50% horizontal screen position when nulling is complete. d. Repeatedly place the probe on and off the inspection surface to generate a lift-off response. Adjust the phase ANGLE until a substantially horizontal, right-to-left lift-off signal is achieved.
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T.O. 33B-1-2
NOTE The lift-off response should move off the left side of the display when the probe is lifted off the part. If it does not, check the inspection frequency, and if required, increase the GAIN until the lift-off signal moves off the screen. e. NULL the probe on the inspection surface. Hold the probe still until nulling is complete. The flying-dot should be located at 50% Full Screen Height (FSH) and 50% Full Screen Width (FSW) when nulling is complete. f. Without re-nulling, place the probe on the reference standard. Compare the horizontal position of the dot when the probe is placed on the reference standard to the horizontal position of the dot when the probe is place on the surface to be inspected. If the flying dot horizontal positions are within three major horizontal divisions, 30% Full Screen Width (FSW), then lift-off compensation is not required. If the flying dot is greater than three major horizontal divisions from the null point then proceed to the step g. NOTE The vertical position of the flying dot is not of concern as the reference standard and part under test may have different conductivity values. g. Insert nonconductive shims between the probe and reference standard until the flying-dot is between 50% and 70% FSW. h. If the total shim thickness exceeds 0.010 inch (10 mils) then the coating SHALL be removed before the inspection is performed. i. If the total shim thickness is 0.010 inch (10 mils) or less then place shims, of the thickness established in step g, on the reference standard for all phases of inspection standardization. Table 4-2. Soft Key FREQ FREQ H-GAIN V-GAIN ANGLE LPF HPF CONT SWEEP V-POS H-POS PERSIST DISP ERS SWPERS DOT/BOX GRATICLE
4-6
Nortec 2000D Initial Settings for Determining Lift-off Compensation Description/Setting MAIN MENU FREQUENCY 1/See Table 4-3 FREQUENCY 2/OFF HORIZ. GAIN/60.0 dB VERT. GAIN/60.0 dB ANGLE/70° FILTER MENU LP FILTER/100 HP FILTER/OFF CONT NULL/OFF DISPLAY MENU SWEEP/OFF V-POS/50% H-POS/50% SCREEN MENU PERSIST/OFF DISP ERASE/OFF OFF DOT ON
Soft Key 1 4 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
Description/Setting SETUP MENU FREQ/SINGLE PRB DR/MID N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
T.O. 33B-1-2
Table 4-3.
Nortec 2000D Inspection Frequencies by Material
Material Alloy 300 and 400 Series Stainless Magnetic Steels Aluminum Inconel Alloys Nickel Alloys Titanium
Frequency 500 kHz - 1 MHz 200 - 500 KHz 200 - 500 kHz 1 - 2 MHz 1 - 2 MHz 2 MHz
4.1.2.1.2 Manual Surface Eddy Current Inspection Scanning Techniques. 4.1.2.1.2.1 General Surface Inspection. Scan the surface to be inspected. Where the direction of cracking is known, scan perpendicular to the direction of cracking. Where the direction of cracking is not known, recommend scanning in the 0, 45 and 90 degree directions. (see Figure 4-3) A scanning index shall be selected to ensure 100% coverage of the inspection area. An acceptable method for ensuring inspection coverage is to coat the inspection with nonaqueous developer and using the trail of probe to indicate coverage. Non-metallic, straight edge, templates, or edge guides should be used to guide the test probe along edges to stabilize the edge effect on the probe.
Figure 4-3.
Required Scanning Directions
4.1.2.1.2.2 Surface Inspection Around Flush Fasteners. Scan around the entire circumference of the fastener. Position the probe’s coil immediately outside the edge of the fastener head. Maintaining a constant yet minimal distance is required to
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T.O. 33B-1-2 maintain sensitivity to cracks propagating from the fastener hole. A circle template made of non-conductive material should be used if part geometry allows. (see Figure 4-4) NOTE Special care must be taken by the inspector to ensure that the probe position is perpendicular to the inspection surface and the template is centered to avoid lift-off and edge effects during scanning. The ability to hold the probe steady and perpendicular during scanning depends on attentiveness, competence, and experience of the inspector.
Figure 4-4.
4-8
Scanning Around Fastener with Flush Heads
T.O. 33B-1-2 4.1.2.1.2.3 Surface Inspection Around Protruding Fastener Heads. Scan around the entire circumference of the fastener, positioning the probe’s coil adjacent yet in contact with the side of the fastener. Using the fastener as a guide, maintain a positive pressure against the fastener head for detection of cracks protruding from under the fastener head. (see Figure 4-5) Re-nulling may be required on the component being inspected due to minor conductivity variations between the part and standard.
Figure 4-5.
Scanning Around Fastener with Protruding Heads
4.1.2.1.2.4 Surface Inspection of Radii. When the direction of cracking is known, scan perpendicular to the direction of cracking. If the cracking direction is not known, scan the radius in both the longitudinal and transverse direction while maintaining the coil perpendicular to the inspection surface. (see Figure 4-6) A scanning index in both the longitudinal and transverse directions shall be selected to ensure complete coverage of the area to be inspected, index spacing shall be selected to ensure 100% coverage of the inspection area. Index spacing at a maximum 1/2 probe diameter is recommended.
Figure 4-6.
Scanning Radii
4.1.2.1.2.5 Scanning Between Fasteners. Scanning between fasteners is identical to scanning around fasteners, however, if the fasteners are too close to allow effective signal interpretation, scan around the perimeter of the fasteners. 4-9
T.O. 33B-1-2 4.1.2.1.2.6 Scanning Edges. Scan part or panel edges using shielded surface probes to reduce edge effect. Nonconductive straight edge or edge guides should be used when part geometry allows. Null with the probe on the edge to minimize edge effect. 4.1.3 General Eddy Current Inspection Procedures. 4.1.3.1 General Information. These procedures prescribe general set-up, calibration and inspection requirements for eddy current instrument standardization and inspection. These instructions are to be used in conjunction with the part specific procedures when they exist. The part specific procedures take priority. If the part specific procedure does not provide guidance or does not exist, this procedure can be used as a stand-alone procedure by an experienced task certified technician for general surface scan requirements. If conditions exist that are not adequately covered contact the appropriate ALC NDI Manager for specific guidance. 4.1.3.2 Part Preparation. 4.1.3.2.1 When conducting eddy current inspections near fuel tank areas, the aircraft must be defueled and purged. Follow the aircraft specific tech data for defuel and purge instructions. CAUTION Surfaces shall be clear of any residue which might interfere with inspection or damage inspection equipment. 4.1.3.2.2 Nonconductive coatings (i.e., paint) in excess of 0.010 inch thick or having wide variation in thickness shall be removed from the inspection area prior to inspection. All sealant SHALL be removed. WARNING Solvents are hazardous material. Handle in compliance with applicable Material Safety Data Sheet (MSDS) and locally approved instructions. Check the weapon specific tech data for approved solvents. 4.1.3.2.3 Remove soils, dirt, grease and other debris which might interfere with inspection or damage inspection equipment. If necessary, clean area with approved solvent. 4.1.3.3 Equipment Preparation. a. Connect eddy current unit to power source if necessary. b. Where possible, all probe coils should be protected by a layer of tape (Teflon or equivalent) with a maximum thickness of 5 mils (0.005 inch). c. The part to be inspected, calibration standard, inspection unit and probe must be at ambient temperature to assure that valid test data is obtained. d. Periodically during the inspection and following the completion of all inspections, rescan the calibration standard to ensure the instrument remains within calibration limits. The time between standardizations SHALL NOT exceed 10minutes. If the original sensitivity requirements are not met following any reference standard rescan, all inspections accomplished since the last successful scan SHALL be reaccomplished. 4.1.3.4 General Procedure for Manual Surface Eddy Current Inspection of Aluminum, Nonferromagnetic Parts, and Weakly Ferromagnetic Parts Using the Staveley Nortec 2000D. 4.1.3.4.1 Equipment Setup. 4.1.3.4.1.1 Establishing Lift-Off Compensation a. Attach the probe and cable to the instrument as required. Apply Teflon tape to the probe as required. b. If the part to be inspected is painted, determine the required lift-off compensation to use during standardization by following the procedure in paragraph 4.1.2.1.1. If the part is not painted proceed to paragraph 4.1.3.4.1.2. 4-10
T.O. 33B-1-2 4.1.3.4.1.2 Stored Setups a. Recall the program and verify the set-up parameters match those listed in Table 4-4. b. Proceed to paragraph 4.1.3.4.2. 4.1.3.4.1.3 If the setup has not been stored in instrument memory, proceed as follows: a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows: (1) Select the SETUP MENU. (2) Select DEFAULT and press ENTER. (3) Select LD DEFLT and press ENTER. (4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER. b. Adjust equipment settings per Table 4-4. Minor adjustments to these settings are allowable as necessary to achieve optimum signal characteristics. c. Set FREQUENCY per specific procedure requirements. If no frequency is specified, use the appropriate frequency as defined in Table 4-5. NOTE Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to the reference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and used in all steps of this procedure especially when inspecting the part and the instrument is displaying corner noise that can be confused with crack-like indications. Table 4-4. Soft Key FREQ FREQ H-GAIN V-GAIN ANGLE LPF HPF CONT SWEEP V-POS H-POS
Nortec 2000D Settings for Surface Scan of Aluminum
Description/Setting MAIN MENU FREQUENCY 1/See Table 4-5 FREQUENCY 2/OFF HORIZ. GAIN/60.0 dB VERT. GAIN/75.0 dB ANGLE/70° FILTER MENU LP FILTER/100 HP FILTER/OFF CONT NULL/OFF DISPLAY MENU SWEEP/OFF V-POS/10% H-POS/80%
Soft Key 1
Description/Setting SETUP MENU FREQ/SINGLE
4 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
PRB DR/MID N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
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T.O. 33B-1-2 Table 4-4. Soft Key PERSIST DISP ERS GRATICLE DOT/BOX
Nortec 2000D Settings for Surface Scan of Aluminum - Continued Description/Setting SCREEN MENU PERSIST/OFF DISP ERASE/OFF ON DOT
Table 4-5.
Soft Key N/A N/A N/A N/A N/A
Description/Setting N/A N/A N/A N/A N/A
Nortec 2000D Inspection Frequencies
Material Alloy Aluminum Titanium Inconel Alloys Nickel Alloys 300 and 400 Series Stainless Magnetic Steels
Frequency 200 kHz 2 MHz 1 - 2 MHz 1 - 2 MHz 500 kHz - 1 MHz 200 - 500 kHZ
4.1.3.4.2 Standardization for Surface Inspection. NOTE If nonconductive shims are required for lift-off compensation then the shims shall be placed on the reference standard during phase adjustment, nulling and establishing sensitivity. a. Allow the part, reference standard, probe and eddy-current instrument to reach ambient temperature to ensure valid, repeatable inspection results. b. Place probe on the calibration standard surface so the coil is a minimum of twice the probe diameter from all notches and edges. Press the NULL key. Hold the probe still until ‘‘Nulling’’ is complete. c. Repeatedly place the probe on and off the reference standard, at least two probe diameters away from all notches and edges, to generate a lift-off response. Adjust the phase ANGLE until a substantially horizontal, right-to-left, lift-off signal is achieved. d. With the appropriate thickness of nonconductive shims placed on the reference standard (if required), place probe on the standard surface so the coil is a minimum of twice the probe diameter from all notches and edges. e. Press the NULL key. Hold the probe still until nulling is complete. f. While repeatedly scanning across the 0.020 inch deep notch adjust the GAIN until a signal trace of 80% Full Screen Height (FSH) deflection is obtained from the notch (see Figure 4-7). Decrease the H-GAIN if the notch signal goes off the left side of the display.
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T.O. 33B-1-2
Figure 4-7.
Signal Response from 0.020 inch Deep Notch in Aluminum
4.1.3.4.3 Sensitivity Check. NOTE If the GAIN maximum limit is reached without achieving the specified deflection, check the lift-off phase angle to ensure it is horizontal. Adjust ANGLE if necessary and reaccomplish standardization. If the required deflection still cannot be achieved change the Probe Drive (PRB DR) to HIGH and repeat standardization. If the required deflection still cannot be achieved or the noise is excessive change probe or cable as required. The step is required when using the Air Force General Purpose Reference Standard. With the appropriate thickness of nonconductive shim in place, scan over the 0.005 inch deep, 0.010 inch deep and 0.020 inch deep reference notches. The three responses should appear similar to (see Figure 4-8). The response from the 0.005 inch deep notch should produce a minimum 5% FSH vertical response and should be clearly discernible from the baseline noise. If these responses are not achieved, check the instrument set-up and repeat the standardization procedure. If after restandardization this sensitivity still cannot be achieved, select a different probe and repeat the standardization.
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T.O. 33B-1-2
Figure 4-8.
Responses from 0.005, 0.010, and 0.020 inch Deep Notches (Aluminum) with Acceptable Signal-to-Noise
4.1.3.4.4 Inspection. a. Place the probe on the part to be inspected. The probe coil should be at least two probe diameters away from the nearest edge. Ensure good contact between the coil and part. b. Press the NULL key and hold the probe still until nulling is complete. Periodic nulling may be necessary during inspection to maintain the baseline at 10% FSH and 80% FSW. NOTE The screen trace or ‘‘flying dot’’ can drift up to 2 major divisions in 15 minutes or less when the Nortec 2000D is initially powered up. Recommend a warm-up period of at least 10 minutes prior to inspection. c. Scan the inspection area. Use the same scan speed as used during calibration. If numerous scan lines are required, index 1/2 the probe diameter between scan lines to ensure full coverage, unless otherwise specified. Watch for indications on the display similar to those obtained during calibration. If specific scan instructions are not provided use the appropriate scan technique defined in (see paragraph 4.1.2.1.2). 4.1.3.4.5 Evaluation, Marking, and Reporting. 4.1.3.4.5.1 Any vertical signal trace that is distinguishable (separated) from the background noise and not caused by lift-off or part geometry shall warrant further examination and rescanning of the area of interest. a. Mark all repeatable crack-like indications equal to or greater than 10% vertical deflection (see Figure 4-8) above the baseline/null point. These areas require evaluation with the part specific back-up procedure. If the part specific procedure does not specify a backup procedure (see paragraph 4.1.3.4.7). b. Any repeatable crack-like indication equal to or greater than 10% FSH above the lift-off baseline that has been verified by the appropriate backup method shall be marked and documented IAW the appropriate AF Instruction and local directives. Enter the percent vertical screen deflection and identify the defect location in the inspection record. 4.1.3.4.6 Post-Inspection Standardization. Place the probe on the standard. Ensure firm contact is maintained between the coil, shim (if used), tape (if used), and standard. a. Ensure the coil is a minimum of two probe diameters from the notch and the nearest edge.
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T.O. 33B-1-2 b. Press the NULL key. Hold the probe on the standard until nulling is complete. c. With the appropriate thickness of shims in place, repeatedly scan across the 0.020 inch deep reference notch. The deflection above the baseline must be between 70% and 90% FSH. If the deflection is below 70% FSH then all inspections performed since the last standardization must be repeated. If the deflection is above 90% then all suspect indications identified since the last standardization must be reevaluated.
Figure 4-9.
Indication Exceeding 10% Vertical Deflection
4.1.3.4.7 Backup Procedure. If the part specific procedure does not specify a backup procedure it is recommended that the indication be verified by a second inspector. Repeat standardization and have a second inspector verify the indication. If available, separate equipment and probes should also be used for each independent inspection. If the defect indication is not confirmed, proceed to system securing. 4.1.3.5 General Procedure for Manual Surface Eddy Current Inspection of Steel Parts Using the Staveley Nortec 2000D. 4.1.3.5.1 Equipment Preparation. 4.1.3.5.1.1 Establishing Lift-off Compensation. a. Attach the probe and cable as required. (See paragraph 4.1 for probe requirements). Apply Teflon tape to the probe as required. b. If the part to be inspected is painted, determine the required lift-off compensation to use during standardization by following the procedure in (see paragraph 4.1.2.1.1). If the part is not painted proceed to (see paragraph 4.1.3.5.1.2). 4.1.3.5.1.2 Stored Setups. a. Recall the program and verify the set-up parameters match those listed in (see Table 4-6). b. Proceed to paragraph 4.1.3.5.2. 4.1.3.5.1.3 If the setup has not been stored in instrument memory, proceed as follows: a. Set the instrument to ‘‘DEFAULT’’ settings. (Refer to the equipment operator’s manual for specific instructions on establishing default settings).
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T.O. 33B-1-2 b. Adjust equipment settings per (see Table 4-6). Minor adjustments to these settings are allowable as necessary to achieve optimum signal characteristics. c. Set FREQUENCY per specific procedure requirements. If no frequency is specified, use the appropriate frequency as defined in (see Table 4-6). NOTE Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to the reference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and used in all steps of this procedure especially when inspecting the part and the instrument is displaying corner noise that can be confused with crack-like indications. Table 4-6. Soft Key FREQ FREQ H-GAIN V-GAIN ANGLE LPF HPF CONT SWEEP V-POS H-POS PERSIST DISP ERS GRATICULE DOT/BOX
Settings Prior to Calibration for Surface Scanning of Steel Parts Description/Setting MAIN MENU FREQUENCY 1/200Khz to 500Khz FREQUENCY 2/OFF HORIZ. GAIN/50.0 dB VERT. GAIN/70.00 dB ANGLE/0° FILTER MENU LP FILTER/30 HP FILTER/0 CONT NULL/OFF DISPLAY MENU SWEEP/OFF V-POS/10% H-POS/50% SCREEN MENU PERSIST/OFF DISP ERASE/5.0 s ON DOT
Soft Key 1
Description/Setting SETUP MENU FREQ/SINGLE
4 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
PRB DRV / MID N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
4.1.3.5.2 Standardization for Surface Inspection of Magnetic Steel. NOTE If a nonconductive shims are required for lift-off compensation then the shims shall be placed on the reference standard during phase adjustment, nulling and establishing sensitivity. If it is difficult at this point to obtain a stable liftoff signal, frequent nulling is required. The lift-off signal will not be completely stable. a. Allow the part, reference standard, probe and eddy current instrument to reach ambient temperature to ensure valid, repeatable inspection results. b. Place probe on the calibration standard surface so the coil is a minimum of twice the probe diameter from all notches and edges. Press the NULL key. Hold the probe still until ‘‘Nulling’’ is complete.
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T.O. 33B-1-2 c. Repeatedly place the probe on and off the reference standard, at least two probe diameters away from all EDM notches and edges, to generate a lift-off response. Adjust the phase ANGLE until a substantially horizontal, right-toleft, lift-off signal is achieved. NOTE • Variations in magnetic permeability may result in excessive noise during standardization. If this is encountered demagnetization of the part may aid in reducing signal noise. Refer to Chapter 3, paragraph 3.1.7.3 Demagnetization Using Portable Yokes for guidance. • If excessive noise is encountered and demagnetization has not reduced the noise to an acceptable level or demagnetization is not possible, it is permissible to utilize High Pass filtering to stabilize the signal. A maximum High Pass filter set at 2 is permitted. d. With the appropriate thickness of nonconductive shims placed on the reference standard (if required), place probe on the standard surface so the coil is a minimum of twice the probe diameter from all notches and edges. (1) Press the NULL key. Hold the probe still until nulling is complete. (2) While repeatedly scanning across the 0.020” deep notch adjust the GAIN until an 80% vertical response is obtained from the notch. The horizontal null position is located at 50% to ensure notch response remains on screen. (see Figure 4-10).
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T.O. 33B-1-2
Figure 4-10.
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80% FSH Signal from a 0.020 Inch Deep Notch
T.O. 33B-1-2
CAUTION The HP filter SHALL NOT exceed 2 Hz and the LP filter shall not be less than 30 Hz or unacceptable signal suppression may result. e. If High Pass filtering is required to stabilize the signal, set the HP FILTER to ‘‘2’’ then perform the following steps: NOTE The use of HP filtration will result in a positive and negative (figure eight) signal presentation on the instrument screen. (1) From the DISPLAY MENU, set the V-POS (vertical position) to 50%. (2) With the appropriate thickness of nonconductive shims placed on the reference standard (if required), place probe on the standard surface so the coil is a minimum of twice the probe diameter from all notches and edges. (3) Press the NULL key. Hold the probe still until nulling is complete. (4) While repeatedly scanning across the 0.020” deep notch at a rate of 0.5-1.0 inches per second, adjust the GAIN until an 80% vertical Peak-to-Peak (PTP) response is obtained from the notch. (see Figure 4-11).
Figure 4-11.
Impedance Plane Display of 80% Ptp Signal from the 0.020 Inch Deep Notch
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T.O. 33B-1-2 4.1.3.5.3 Sensitivity Check. CAUTION Scanning speed is critical when using HPF. HPF is necessary to stabilize the signal on magnetic materials. However, HPF is very sensitive to inadequate scanning speed, which can suppress crack signals. Ensure a 0.5-1.0 inch per second scanning speed is maintained during calibration and inspection to prevent suppressing notch and crack signals. It is helpful to practice the scanning speed during calibration. With the appropriate thickness of nonconductive shim in place, scan over the 0.005 inch deep reference notch. The response from the notch should be clearly distinguishable from the baseline noise and produce a minimum 20% FSH response (20% PTP with High Pass filtering). (See Figure 4-12 and Figure 4-13) If this response is not achieved, check the instrument set-up and repeat the standardization procedure. If after restandardization this sensitivity still cannot be achieved, select a different probe and repeat the standardization.
Figure 4-12.
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Impedance Plane Response (without High Pass Filter) from the 0.005 Inch Notch (4340 Steel) with Acceptable Signal-To-Noise
T.O. 33B-1-2
Figure 4-13.
Impedance Plane Response (with High Pass Filter) from the 0.005 Inch Notch (4340 Steel) with Acceptable Signal-To-Noise
4.1.3.5.4 Inspection. a. Place the probe on the part to be inspected. The probe coil should be at least two probe diameters away from the nearest edge. Ensure good contact between the coil and part. b. Scan the inspection area. Use a similar scan speed as used during calibration. If numerous scan lines are required, index 1/2 the probe coil diameter between scan lines to ensure full coverage. Watch for indications on the display similar to those obtained during calibration. Ensure a scanning speed of 0.5-1.0 per second is maintained. If specific scan instructions are not provided use the appropriate scan technique defined in (see paragraph 4.1.2.1.2). c. During the inspection (10-minute intervals) and following the completion of all inspections, rescan the calibration standard to ensure the instrument remains within calibration limits. With the appropriate thickness of shims in place, repeatedly scan across the 0.020 inch deep reference notch. The deflection above the baseline must be between 70% and 90% FSH (70% and 90% PTP with HP filter). If the deflection is below 70% FSH then all inspections performed since the last standardization must be repeated. If the deflection is above 90% then all suspect indications identified since the last standardization must be reevaluated. 4.1.3.5.5 Evaluation, Marking, and Reporting. a. With an approved marking pencil, mark all repeatable crack-like indications distinguishable (separated) from background noise. (see Figure 4-12 or Figure 4-13) b. Evaluate all marked indications with the part specific back-up procedure. If the part specific procedure does not specify a back-up procedure (see paragraph 4.1.3.5.7). c. Report any repeatable crack-like indication obtained during the back-up procedure inspection that exceed two times the background noise level amplitude or 20% deflection if the noise is near zero. Enter the percent screen deflection and defect location in the inspection record. 4.1.3.5.6 Post-Inspection Standardization. a. Place the probe on the standard. Ensure firm contact is maintained between the coil, shim (if used), tape (if used), and standard.
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T.O. 33B-1-2 b. Ensure the coil is a minimum of two probe diameters from the notch and the nearest edge. c. Press the NULL key. Hold the probe on the standard until nulling is complete. d. With the appropriate thickness of shims in place, repeatedly scan across the 0.020 inch deep reference notch. The deflection above the baseline must be between 70% and 90% FSH. If the deflection is below 70% FSH then all inspections performed since the last standardization must be repeated. If the deflection is above 90% then all suspect indications identified since the last standardization must be reevaluated. 4.1.3.5.7 Backup Procedure. If the part specific procedure does not specify a backup procedure, evaluate all marked indications as follows: Recalibrate per (see paragraph 4.1.3.5.2) and perform a redundant inspection of all areas exhibiting suspect indications. A redundant inspection is defined as an inspection performed by a second individual. Each independent inspection shall include a separate setup and calibration of the equipment. If available, separate equipment and probes should also be used for each independent inspection. If no defect is suspected or confirmed, proceed to system securing. 4.1.3.6 General Procedure for Rotary Fastener Hole Eddy Current Inspection of Aluminum, Non-ferrous and Weakly Ferromagnetic Parts Using the Staveley Nortec 2000D/2000D+ with a MiniMite, Spitfire and RA/19 Scanners. NOTE This procedure does not apply to titanium alloys. Refer to Section 4.1.8 for specific procedures to be used for rotary fastener hole inspection of titanium alloys. 4.1.3.6.1 Equipment Preparation. a. Ensure part, reference standard and probe are at ambient temperature to ensure valid, repeatable inspection results. b. Select the probe for best fit in the hole to be inspected. When inserted into the hole, the probe should be in intimate contact with the inner diameter but still rotate easily. c. Application of Teflon tape (5 mils maximum thickness) to the probe is required to reduce probe wear and signal noise caused by scanning rough surfaces and hole edges. Wrap the tape over the coil and through the probe split. Do not wrap the tape completely around the probe split. NOTE The Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to the reference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and used in all steps of this procedure. d. Connect the probe to the scanner and connect the scanner cable to the scanner and eddycurrent unit. 4.1.3.6.1.1 Stored Setups. a. Recall the program. Verify the settings match those listed in Table 4-7. b. Proceed to paragraph 4.1.3.6.2. 4.1.3.6.1.2 If the setup has not been stored in instrument memory, proceed as follows: a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows: (1) Select the SETUP MENU. (2) Select DEFAULT and press ENTER. (3) Select LD DEFLT and press ENTER. (4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER.
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T.O. 33B-1-2 b. Adjust equipment settings per Table 4-7. Minor adjustment to these settings are allowed as necessary to achieve optimum signal characteristics. c. Set the FREQUENCY in accordance with the part specific procedure. If no frequency is specified, use the probe frequency as specified in Table 4-8 for the specific material to be inspected. For all other materials contact the Air Logistics Center NDI Manager. d. Note the hole diameter to be inspected and adjust the Low Pass Filter (LP FILTER) and High Pass Filter (HP FILTER) to the values shown in Table 4-9. Table 4-7. Soft Key FREQ FREQ H-GAIN V-GAIN ANGLE CONT SWEEP V-POS H-POS PERSIST DISP ERS GRATICULE DOT/BOX
Nortec 2000D Calibration Settings Scanning of Aluminum Fastener Holes Description/Setting MAIN MENU FREQUENCY 1/(See Table 4-8) FREQUENCY 2/OFF HORIZ. GAIN/65.0 dB VERT. GAIN/65.00 dB ANGLE/0° FILTER MENU CONT NULL/OFF DISPLAY MENU SWEEP/OFF V-POS/50% H-POS/50% SCREEN MENU PERSIST/OFF DISP ERASE/0.2 s ON DOT
Soft Key 1
Description/Setting SETUP MENU FREQ/SINGLE
4
PRB DRV/MID
RPM SYNC ANG
SPECIAL MENU SCAN RPM/1500 0
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T.O. 33B-1-2
Table 4-8.
Frequency Settings Fastener Hole Scanning of Aluminum, Non-Ferrous Alloys, and Weakly Ferromagnetic Alloys
Material Alloy Aluminum 300 and 400 Series Stainless Magnetic Steel Nickel Alloys Magnesium Inconel Alloys
Frequency 200 KHz - 500 KHz 500 KHz - 1 MHz 200 - 500 KHz 1 - 2 MHz 500 KHz 1 MHz - 2 MHz
NOTE In cases where a frequency range is provided, high frequencies will provide more sensitivity to cracks, while low frequencies will produce lower noise levels during inspection.
Table 4-9.
Filter
LPF HPF NOTE: Filters
Filter Settings vs. Hole Diameter
Probe Diameter 5/32″-7/32″/0.156>7/32″-5/16″/0.219>5/16″0.219″ 0.312″ 7/16″/0.3120.437″ 500 500 700 150 200 300 may be adjusted +/-50Hz to improve symmetry of notch response.
>7/16″-3/4″/0.4370.750″ 1500 5005
4.1.3.6.2 Standardization for Rotary Fastener Hole Inspection of Aluminum, Selected Nonferromagnetic and Weakly Ferromagnetic Parts. NOTE This procedure was developed using a differential/reflection, fastener hole probe, 100KHz- 2MHz. The differential/reflection coil design will portray a negative and positive (figure eight) signal response on the impedance plane display of the instrument. a. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probe should fit snug in the hole without binding. Verify the coil is 90° away from the corner notch and away from hole edges and press NULL. Hold the probe still until nulling is complete. b. Remove the probe from the hole. c. With the SWEEP turned OFF, hold the scanner so that the probe is parallel to the reference standard. Place the coil in contact with a flat area of the reference standard at least 1/4 inch away from any edge or notch. Turn the scanner on while the coil makes contact with the reference standard to generate a liftoff signal. d. Adjust the phase rotation by pressing the ANGLE key and rotating the Smartknob to achieve a substantially horizontal liftoff signal. See Figure 4-14.
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T.O. 33B-1-2
Figure 4-14.
Typical Lift-off Response with Phase Adjusted Correctly
e. Turn the scanner on and insert the rotating probe into the appropriate hole size in the reference standard and locate the 0.030 inch corner notch located at the interface of the first and second layers. Maximize the reference notch signal. f. Adjust the Vertical GAIN (V-GAIN) and Horizontal GAIN (H-GAIN) independently to place the entire notch response on the screen at a 45 degree angle (1:1 slope), spanning 80% FSH and 80% FSW. (See Figure 4-15). Notch peak-to-peak response at 80% FSH and 80% FSW (45 degrees). The lift-off may not be visible. g. Return to the DISPLAY menu. Press the SWEEP key twice to enter the ‘‘SWEEP EXTRN’’ mode. The instrument is now in sweep mode. h. If the sweep signal is centered at 50% FSH, proceed to step k. i. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probe should fit snug in the hole without binding. Verify the coil is 90° away from the corner notch and away from hole edges and press NULL. Hold the probe still until nulling is complete. j. Remove the probe from the hole.
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T.O. 33B-1-2
Figure 4-15.
Figure 4-16.
4-26
Impedance Plane Display
Properly Calibrated Sweep Display
T.O. 33B-1-2
Figure 4-17.
Figure 4-18.
Acceptable Noise Level from Clean Hole
30% PTP Signal Requires Evaluation
k. Turn the scanner on and reinsert into the reference standard hole. Maximize the signal from the 0.030 inch interface notch. Push the GAIN button and adjust the GAIN (both horizontal and vertical gains will be adjusted simultaneously) as necessary to obtain an 80% Peak-to-Peak (PTP) signal from the notch. The notch signal should appear narrow and nearly symmetric above and below the baseline as shown in Figure 4-16.
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T.O. 33B-1-2 l. Ensure the signal response from good areas of the hole is relatively smooth across the sweep display. Noise level in good areas shall be no more than 10% negative or positive from the baseline. See Figure 4-17. m. If the noise level is less than 10% from the baseline or less, proceed to paragraph 4.1.3.6.3 n. If noise signals greater than 10% from the baseline appear, repeat standardization procedure. If the noise level remains excessive after repeated standardization, perform the following steps: (1) Recheck probe fit. (2) Remove probe from scanner and check for inherent scanner and cable noise. (3) Replace the probe, cable or scanner that is causing the noise and repeat standardization per section 4.1.3.6.2. 4.1.3.6.3 Determining Maximum Index Speed. a. Insert the probe into the appropriate hole in the reference standard and locate the 0.030 inch interface notch at the interface of the first and second layers. b. Monitor the display while moving the probe in and out over the interface notch. NOTE The maximum speed that the probe can be moved through the hole is the rate of probe travel that always identifies the notch and does not cause a reduction of the peak in signal height from 80% FSH PTP. c. Gradually increase the probe travel speed until the peak height of the notch response begins to decrease below 80% FSH PTP. This is the maximum probe travel speed. 4.1.3.6.4 Identifying the Scanner Zero or Scan Origin. Establish the scanner zero or scan origin by using one of the following methods: 4.1.3.6.4.1 Method A: Setting the Scanner Sync Zero Position. a. Visually locate the notch on the top surface of the reference standard. b. Insert the probe into the appropriate hole in the reference standard and rotate the scanner housing until the red LED alarm indicator on the side of the scanner housing is pointed at the physical position of the notch on the standard as shown in Figure 4-19 and Figure 4-20. c. Turn on the scanner and adjust the SYNC ANGLE in the SPECIAL menu screen until the trailing edge of the notch indication is displayed on the left side of the screen with the leading edge of the indication positioned on the right side of the screen (split-signal) as shown in Figure 4-19. NOTE An acceptable alternate approach is to place the notch signal in the center of the screen and use this position as the scanner zero. 4.1.3.6.4.2 Method B: Locating Sweep Crossing for Scanner/Notch Alignment. a. Visually locate the notch on the top surface of the reference standard. b. Insert the rotating probe into the appropriate hole in the reference standard until the maximum signal is obtained from the notch. c. Rotate the scanner until the top, center of the scanner is in line with the notch. d. Note the point at the center of the notch signal crosses the sweep baseline. This is scanner zero as shown in Figure 4-21.
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T.O. 33B-1-2 e. Locate crack position by rotating the scanner until crack signal appears at the scanner zero location. Crack will be in line with the top, center of the scanner.
Figure 4-19.
Establishing Sync Zero Position of the Nortec Spitfire Scanner
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T.O. 33B-1-2
Figure 4-20.
Figure 4-21.
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Establishing Sync Zero Position of the Nortec Minimite Scanner
Establishing Top, Center Scanner Zero Position (Method B)
T.O. 33B-1-2 4.1.3.6.5 Alarm Setting 4.1.3.6.5.1 Nortec 2000D. a. With the display in the sweep mode (SWEEP/EXTRN), press DISP/ALARM to set the sweep display ALARM to the settings in Table 4-10. See Figure 4-22. Table 4-10. TYPE +/-/OFF TOP BOTTOM
Sweep Display Alarm Gate Settings SWEEP NEGATIVE 65.0% 35.0%
Figure 4-22.
Sweep Display with Alarm Gates
b. Return to the DISPLAY menu. Press the SWEEP key to turn the display to SWEEP/OFF. The display should now be in the impedance plane mode. Set the impedance plane display ALARM to settings in Table 4-11. See Figure 4-23. Table 4-11. TYPE +/-/OFF TOP BOTTOM RIGHT LEFT
Impedance Plane Display Alarm Gate Settings BOX NEGATIVE 65.0% 35.0% 65.0% 35.0%
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T.O. 33B-1-2
Figure 4-23.
Impedance Plane Display with Alarm Gates
4.1.3.6.5.2 Nortec 2000D+. a. Return to the DISPLAY menu. Press the SWEEP key to turn the display mode to EXT SPLT mode. The display should now be in the split screen mode (sweep display on the left and impedance plane display on the right. Set ALARM to settings in Table 4-10 (left side of screen). See Figure 4-24, left side. NOTE The Nortec 2000D+ will only allow alarm settings on the sweep half of the display in the split screen mode. b. With a grease pencil, mark two vertical lines on the impedance plane half of the display (right side), one at 35% FSW and the second at 65% FSW. The lines must pass through the 50% FSH baseline. See Figure 4-24, right side. This defines the limits for lift-off induced noise.
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T.O. 33B-1-2
Figure 4-24.
Split Screen Display with Sweep Display Alarm Gates and Impedance Plane Display Lift-off Limits
4.1.3.6.6 Inspection. NOTE • Standardization should be verified at least once every 10 minutes or every 30 holes, whichever comes first. If the notch signal does not provide 70-90% vertical PTP deflection repeat the standardization IAW paragraph 4.1.3.6.2 and repeat the inspection. • All holes SHOULD be cleaned with a tool such as a flex hone prior to inspection. a. Visually verify the hole surface condition will not damage the probe during inspection and is void of any foreign material (e.g. grease, sealant, metal shavings). b. Enter data available to this point on an inspection record, if required. Enter additional data in record as it is obtained. c. With the scanner off, check probe fit in the holes to be inspected. The fit should approximate the fit in the reference standard. Remove the probe from the hole. 4.1.3.6.6.1 Inspection with the Nortec 2000D. a. With the SWEEP mode OFF (impedance plane display), turn on the scanner and reinsert the probe in the hole. Inspect by slowly pushing the probe through the entire hole then pulling the probe slowly back through the hole. The probe must be kept perpendicular to the part surface during scanning. Repeat a minimum of twice for each hole to be inspected. b. The hole is considered uninspectable if the general surface condition causes noise signals greater than 10% above or below the baseline on the sweep display. (See Figure 4-26). Additional hole preparation and cleaning may be required prior to reinspection. c. Indications on the impedance plane appearing near the same phase angle as the calibration notch (upper left or lower right quadrant of display) and exceed 30% FSH from the baseline (see Figure 4-25) proceed to paragraph 4.1.3.6.7. For all other indications exceeding the inspection gates, proceed to paragraph 4.1.3.6.10 for disposition.
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T.O. 33B-1-2
Figure 4-25.
Figure 4-26.
Example of Crack Indication in Hole with Noise Level Greater than 30%Fsw
Example of Excessive Noise in the Sweep Mode (Left) and in the Impedance Plane Mode (Right)
4.1.3.6.6.2 Inspection with the Nortec 2000D+. a. Return to the DISPLAY menu. Press the SWEEP key to turn the display to EXT SPLT mode. The display should now be in the split screen mode (sweep display on the left and impedance plane display on the right. b. Turn on the scanner and reinsert the probe in the hole. Inspect by slowly pushing the probe through the entire hole then pulling the probe slowly back through the hole. The probe must be kept perpendicular to the part surface during scanning. c. The hole is considered uninspectable if the general surface condition causes noise signals greater than 10% above or below the baseline on the sweep display (see Figure 4-27). Hole preparation and cleaning may be required prior to reinspection. d. Indications on the impedance plane appearing near the same phase angle as the calibration notch and exceed 30% FSH from the baseline (see Figure 4-24) proceed to paragraph 4.1.3.6.7. For all other indications which exceed the inspection gates, proceed to 4.1.3.6.10 for disposition. 4.1.3.6.7 Indication Evaluation, Marking, and Recording. a. Any repeatable indication above the background noise, exhibits a vertical response greater than 30% vertical PTP in the sweep display (Figure 4-25) and exhibits a phase response similar to the reference notch when viewed in the 4-34
T.O. 33B-1-2 impedance plane display (Figure 4-25), shall be considered a possible crack. This SHALL be considered a crack even with lift-off noise greater than 30% FSW. b. Mark all repeatable crack indications with an approved marker per paragraph 4.1.3.6.8 and paragraph 4.1.3.6.9. c. Verify the instrument standardization after the detection of a crack indication by performing a sensitivity check of the unit as follows: (1) Insert the probe into the appropriate reference standard hole and maximize the signal response received from the reference notch. (2) The notch signal should exhibit a vertical signal within 70% - 90% PTP. If it does then the defect indication SHALL be considered valid and recorded. (3) If the notch signal does not provide the required 70% - 90% vertical PTP deflection then repeat the standardization in accordance with paragraph 4.1.3.6.2 and repeat the inspection. 4.1.3.6.8 Identifying the Circumferential Location of an Indication. a. Observe the indication in the sweep mode. Maximize the indication response. b. Identify the radial location by rotating the scanner to bring the displayed indication to the sweep line zero position that was identified in paragraph 4.1.3.6.4. c. Using an approved marker, place a mark on the part surface in line with the scanner zero point. 4.1.3.6.9 Identifying the Length of a Crack-Like Indication Down the Bore of a Hole (If Required). a. Without covering the face of the probe, wrap the probe shaft with a piece of masking tape. b. Hold an approved fine-tipped marker parallel to the part surface with the marking point pointing toward the probe shaft. c. Observe the indication in the sweep mode. d. Insert the probe into the hole containing the crack-like indication. e. As the probe is scanned through the hole use the marker to make a mark on the masking tape when the crack indication first reaches 30% FSH PTP. f. Continue to scan in the hole. Use the marker to make a second mark on the masking tape when the indication height drops back to 30% FSH PTP. g. Determine the indication length by measuring the distance between the marks on the masking tape. Use a ruler with the appropriate scale. 4.1.3.6.10 Backup Procedures and Disposition of Non-Crack Indications. Indications with a phase response different from the reference notch exhibiting greater than 30% vertical PTP response indicate hole contamination or damage. Additional hole preparation, reaming and/or cleaning may be required prior to reinspection. a. If horizontal lift-off is greater than 30% FSW on the impedance display check for out-of-round condition or interface noise (see Figure 4-26). If allowed, have the hole reamed and then reinspect. Multi-layer structures may create irrelevant noise. b. If no specific back-up procedure is available, verify crack indication using a another inspector and set-up. If possible, use different equipment and probes. 4.1.3.7 General Procedure for Rotary Fastener Hole Eddy Current Inspection of Magnetic Steel Parts Using the Staveley NORTEC-2000D/2000D+ With a MiniMite, Spitfire or RA/19 Scanners. 4.1.3.7.1 Equipment Preparation. a. Ensure part, reference standard and probe are at ambient temperature to ensure valid, repeatable inspection results.
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T.O. 33B-1-2 b. Select the probe for best fit in the hole to be inspected. When inserted into the hole the probe should be in intimate contact with the inner diameter but still rotate easily. c. Application of Teflon tape to the probe is required (5 mils maximum thickness) to reduce probe wear and signal noise caused by scanning rough surfaces. Wrap the tape over the coil and through the probe split. Do not wrap the tape completely around the probe split. NOTE • Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to the reference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and used in all steps of this procedure especially when inspecting the part and the instrument is displaying corner noise that can be confused with crack-like indications. • Some ferromagnetic materials may exhibit excessive noise due to variations in magnetic permeability. If this is encountered, demagnetization of the part, before inspection, may help reduce the noise to acceptable levels. d. Connect the probe to the scanner and connect the scanner cable to the scanner and eddycurrent unit. 4.1.3.7.1.1 Stored Setups. a. Recall the program. Verify the settings match those listed in Table 4-12. b. Perform standardization per paragraph 4.1.3.7.2. 4.1.3.7.1.2 If the setup has not been stored in instrument memory, proceed as follows: a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows: (1) Select the SETUP MENU. (2) Select DEFAULT and press ENTER. (3) Select LD DEFLT and press ENTER. (4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER. b. Adjust equipment settings (see Table 4-12). Minor adjustments to these settings are allowable as necessary to achieve optimum signal characteristics. c. Set FREQUENCY per specific procedure requirements. If no frequency is specified, use 500 KHz for 4000 series steels. For all other types of steel contact the Air Logisitics Center NDI Manager. Minor adjustments from this guideline are allowable as necessary to achieve optimum signal characteristics. d. Note the hole diameter to be inspected and adjust the Low Pass Filter and High Pass Filter to the values shown in Table 4-13. Table 4-12.
Settings Prior to Calibration of Nortec 2000D/2000D+ Fastener Hole Scanning of Magnetic Steel Parts
Soft Key FREQ FREQ H-GAIN V-GAIN
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Description/Setting MAIN MENU FREQUENCY 1/500KHz FREQUENCY 2/OFF HORIZ. GAIN/65.0 dB VERT. GAIN/65.0 dB
Soft Key 1 4
RPM
Description/Setting SETUP MENU FREQ/SINGLE PRB DRV/MID SPECIAL MENU MiniMite and Spitfire SCAN RPM/1500
T.O. 33B-1-2 Table 4-12.
Settings Prior to Calibration of Nortec 2000D/2000D+ Fastener Hole Scanning of Magnetic Steel Parts - Continued
Soft Key
Description/Setting
Soft Key
ANGLE
ANGLE/0° FILTER MENU CONT NULL/OFF DISPLAY MENU SWEEP/OFF V-POS/50% H-POS/50% SCREEN MENU PERSIST/OFF DISP ERASE/0.2 s ON DOT
SYNC ANG
CONT SWEEP V-POS H-POS PERSIST DISP ERS GRATICULE DOT/BOX
Table 4-13.
Filter
LPF HPF NOTE: Filters
Description/Setting R/A 19 Scanner SCAN RPM/1200 0
Filter Settings vs. Hole Diameter
Probe Diameter 5/32″-7/32″/0.156>7/32″-5/16″0.219>5/16″0.219″ 0.312″ 7/16″/0.3120.437″ 500 500 700 150 200 300 may be adjusted +or-50Hz to improve symmetry of notch response.
>7/16″-3/4″/0.4370.750″ 1500 500
4.1.3.7.2 Standardization for Rotary Fastener Hole Inspection of Magnetic Steel Parts. NOTE This procedure was developed using a differential/reflection, fastener hole probe, 100KHz-1MHz. The differential/reflection coil design will portray a negative and positive (figure eight) signal response on the impedance plane display of the instrument. a. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probe should fit snug in the hole while rotating freely without binding. Verify the coil is 90º away from the notches and away from hole edges and press NULL. Hold the probe still until nulling is complete. b. Remove the probe from the hole. c. With the SWEEP turned OFF, hold the scanner so that the probe is parallel to the reference standard. Place the coil in contact with a flat area of the reference standard at least 1/4 inch away from any edge or notch. Turn the scanner on while the coil makes contact with the reference standard to generate a liftoff signal.
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T.O. 33B-1-2
Figure 4-27.
Lift-off Response with Phase Adjusted Correctly
d. Adjust the phase rotation by pressing the ANGLE key and rotating the Smartknob to achieve a substantially horizontal lift-off signal. (See Figure 4-27). The lift signal may appear slightly different from that in the figure, but should be horizontal. e. Turn the scanner on and insert the probe into the appropriate size hole in the reference standard and locate the 0.030inch corner notch located at the interface of the first and second layers. f. Adjust the GAIN to place the entire notch response on the screen. Ensure the signal from the notch is separated from the lift-off signal by a minimum slope of 1:2 (Y:X) (30 degrees). (See Figure 4-28). g. If the notch response does not provide at least a 1:2 separation from the lift-off, check to be sure the lift-off response is horizontal. If the lift-off response is horizontal yet the notch response does not provide at least a 1:2 (Y:X) slope, select a different probe and repeat the standardization.
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T.O. 33B-1-2
Figure 4-28.
Idealized Response Illustrating Minimum Separation Between Lift-off and EDM Notch Response
h. Return to the DISPLAY menu. Press the SWEEP key twice to enter the ‘‘SWEEP EXTRN’’ mode. i. If the sweep signal is centered at 50% FSH, proceed to step a. j. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probe should fit snug in the hole while rotating freely without binding. Verify the coil is 90º away from the notches and away from hole edges and press NULL. Hold the probe still until nulling is complete. k. Remove the probe from the hole. l. Turn the scanner on and reinsert into the reference standard hole. Maximize the signal from the 0.030 inch interface notch. Push the GAIN button and adjust the GAIN (both horizontal and vertical gains will be adjusted simultaneously) as necessary to obtain an 80% Peak-to-Peak (PTP) signal from the notch. The notch signal should appear narrow and nearly symmetric above and below the baseline as shown in (Figure 4-29).
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T.O. 33B-1-2
Figure 4-29.
Figure 4-30.
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Properly Calibrated Sweep Display (Steel)
Acceptable Noise Level from Clean Hole (Steel)
T.O. 33B-1-2
Figure 4-31.
Signal from Hole Subject to Evaluation (Steel)
m. Ensure the signal from good areas of the notched hole, are relatively smooth across the sweep display. Noise level in good areas shall be no more than 10% negative or positive from the baseline. (See Figure 4-30) n. If the noise level is less than 10% from the baseline, proceed to paragraph 4.1.3.7.3. o. If the noise level is greater than 10% from the baseline, repeat standardization procedure. If the noise level remains above 10% from the baseline after repeated standardization, perform the following steps: (1) Recheck probe fit. (2) Remove probe from scanner and check for inherent scanner and cable noise. (3) Replace the probe, cable or scanner that is causing the noise and repeat standardization procedure. 4.1.3.7.3 Determining Maximum Index Speed. a. Insert the probe into the appropriate hole in the reference standard and locate the notch at the interface of the first and second layers. b. Monitor the display while moving the probe in and out over the interface notch. NOTE The maximum speed that the probe can be moved through the hole is the rate of probe travel that always identifies the notch and does not cause a reduction the peak in signal height from 80% vertical PTP. c. Gradually increase the probe travel speed until the peak height of the notch response begins to decrease below 80% vertical PTP. This is the maximum probe travel speed. 4.1.3.7.4 Identifying the Scanner Zero or Scan Sweep Origin. Establish the scanner zero or scan origin by using one of the following methods:
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T.O. 33B-1-2 4.1.3.7.4.1 Method A: Setting the Sync Zero Position. a. Visually locate the notch on the top surface of the reference standard. b. Insert the probe into the appropriate hole in the reference standard and rotate the scanner housing until the red LED alarm indicator on the side of the scanner housing is pointed at the physical position of the notch on the standard as shown in (Figure 4-32 and Figure 4-33). c. Turn on the scanner and adjust the SYNC ANGLE in the SPECIAL menu screen until the trailing edge of the notch indication is displayed on the left side of the screen with the leading edge of the indication positioned on the right side of the screen (split-signal) as shown in (Figure 4-32). NOTE An acceptable alternate approach is to place the notch signal in the center of the screen and use this position as the scanner zero. 4.1.3.7.4.2 Method B: Locating Sweep Crossing for Scanner/Notch Alignment. a. Visually locate the notch on the top surface of the reference standard. b. Insert the rotating probe into the appropriate hole in the reference standard until the maximum signal is obtained from the notch. c. Rotate the scanner until the top, center of the scanner is in line with the notch. d. Note the point at the center of the notch signal crosses the sweep baseline. This is scanner zero as shown in (Figure 4-34). e. Locate crack position by rotating the scanner until crack signal appears at the scanner zero location. Crack will be in line with the top, center of the scanner.
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T.O. 33B-1-2
Figure 4-32.
SYNC Zero Position of the Nortec Spitfire Scanner (Steel)
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T.O. 33B-1-2
Figure 4-33.
SYNC Zero Position of the Nortec MiniMite Scanner (Steel)
Figure 4-34.
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SYNC Zero Position (Method B) (Steel)
T.O. 33B-1-2 4.1.3.7.5 Alarm Settings. Alarm use is optional unless otherwise specified in the procedure. See the operator’s manual for alarm setting instructions. 4.1.3.7.6 Inspection. NOTE • Standardization of the unit should be verified at least every 10 minutes or after inspection of 30 holes whichever is sooner. If standardization check sensitivity is not at least 70% of PTP all inspections accomplished since the last successful calibration check must be repeated. • Some ferromagnetic materials may exhibit excessive noise due to variations in magnetic permeability. Demagnetizing the part before inspection may help reduce the noise to acceptable levels. a. Visually verify the hole surface condition will not damage the probe during inspection and is void of any foreign material (e.g. grease, sealant, metal shavings). All holes SHOULD be cleaned with a tool such as a flex hone prior to inspection. b. Enter data available to this point on an inspection record, if required. Enter additional data in record as it is obtained. c. Press SWEEP so SWEEP EXTRN appears in the display. This indicates the inspection is being performed in the sweep mode. d. With scanner off, check probe fit in the holes to be inspected. The fit should approximate the fit in the calibration standard. e. Turn on the scanner and reinsert the probe in the hole. Inspect the hole by slowly pushing the probe through the entire hole and then pulling the probe slowly back through the hole. The probe must be kept perpendicular to the part surface during scanning. Repeat a minimum of twice for each hole to be inspected. f. The hole is considered uninspectable if the general surface condition causes noise signals greater than 10% above or below the baseline on the sweep display. (See Figure 4-30) Additional hole preparation and cleaning may be required prior to reinspection. 4.1.3.7.7 Indication Evaluation, Marking, and Recording. a. Any repeatable indication above the background noise that exhibits a vertical response equal to or greater than 30% vertical PTP (See Figure 4-31) and appears similar the signal obtained from the reference standard shall be considered a possible crack. b. Using an approved marker, mark all repeatable crack-like indications. (see paragraph 4.1.3.7.8 and paragraph 4.1.3.7.9) c. Verify the instrument standardization after the detection of a crack indication by performing a sensitivity check of the unit as follows: (1) Insert the probe into the appropriate reference standard hole and maximize the signal response received from the notch. (2) The maximized notch signal should exhibit a vertical signal 70% - 90% PTP. If it does, then the defect indication SHALL be considered valid and recorded. (3) If notch signal does not provide the required 70% - 90% vertical PTP deflection then repeat the standardization in accordance with paragraph 4.1.3.7.2 and repeat the inspection. 4.1.3.7.8 Identifying the Circumferential Location of an Indication. a. Maximize the indication response. b. Identify the radial location by rotating the scanner to bring the displayed indication to the sweep line zero position (left side of screen).
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T.O. 33B-1-2 c. Using an approved marker, place a mark on the part surface in line with the scanner zero point that was identified in (see paragraph 4.1.3.6.4). 4.1.3.7.9 Identifying the Length of a Crack-Like Indication Down the Bore of a Hole (If Required). a. Without covering the face of the probe, wrap the probe shaft with a piece of masking tape. b. Hold an approved fine-tipped marker parallel to the part surface with the marking point pointing toward the probe shaft. c. Insert the probe into the hole containing the crack-like indication. d. As the probe is scanned through the hole, use the marker to make a mark on the masking tape when the crack indication first reaches 30% FSH PTP. e. Continue to scan in the hole. Use the marker to make a second mark on the masking tape when the indication height drops back to 30% FSH PTP. f. Determine the indication length by measuring the distance between the marks on the masking tape. Use a ruler with the appropriate scale. 4.1.3.7.10 Backup Procedure. If the part specific procedure does not specify a backup procedure it is recommended that the indication be verified by a second inspector. Repeat standardization per (paragraph 4.1.3.7.2) and have a second inspector verify the indication. If available, separate equipment and probes should also be used for each independent inspection. If the defect indication is not confirmed, proceed to system securing. 4.1.3.8 General Procedure for Rotary Fastener Hole Eddy Current Inspection of Titanium Parts Using the Staveley Nortec 2000D with a Minimite, Spitfire, and RA/19 Scanners. 4.1.3.8.1 Equipment Preparation. a. Ensure part, reference standard and probes are at ambient temperature to ensure valid, repeatable inspection results. b. Select the probe for best fit in the hole to be inspected. When inserted into the hole, the probe should be in intimate contact with the inner diameter but still rotate easily. c. Application of Teflon tape (5 mils maximum thickness) to the probe is required to reduce probe wear and signal noise caused by scanning rough surfaces and hole edges. Wrap the tape over the coil and through the probe split. Do not wrap the tape completely around the probe split. NOTE The Teflon tape may need to be replaced periodically. Always confirm unit standardization responses to the reference standard notches after the tape is replaced. It is critical to ensure that tape is applied correctly and used in all steps of this procedure. d. Connect the probe to the scanner and connect the scanner cable to the scanner and eddycurrent unit. 4.1.3.8.1.1 Stored Setups. a. Recall the program. Verify the settings match those listed in Table 4-14. b. Proceed to paragraph 4.1.3.8.2 4.1.3.8.1.2 If the setup has not been stored in instrument memory, proceed as follows: a. Set the instrument to ‘‘DEFAULT’’ settings by performing the steps as follows: (1) Select the SETUP MENU. (2) Select DEFAULT and press ENTER. (3) Select LD DEFLT and press ENTER. 4-46
T.O. 33B-1-2 (4) Rotate the Smartknob until ‘‘CONFIRM’’ appears on the lower left side of the display and press ENTER. b. Adjust equipment settings per Table 4-14. Minor adjustment to these settings are allowed as necessary to achieve optimum signal characteristics. c. Set the FREQUENCY in accordance with the part specific procedure. If no frequency is specified, use 2 MHz. d. Note the hole diameter to be inspected and adjust the Low Pass Filter (LP FILTER) and High Pass Filter (HP FILTER) to the values shown in Table 4-15. Table 4-14.
Nortec 2000D Initial Calibration Settings for Rotary Scanning of Fastener Holes in Titanium Parts
Soft Key FREQ FREQ H-GAIN V-GAIN ANGLE
CONT
SWEEP V-POS H-POS PERSIST DISP ERS GRATICULE DOT/BOX
Description/Setting MAIN MENU FREQUENCY 1/2MHz FREQUENCY 2/OFF HORIZ. GAIN/65.0 dB VERT. GAIN/65.0 dB 0° FILTER MENU (See Table 4-14 for filter settings) CONT NULL/OFF
Soft Key
DISPLAY MENU SWEEP/OFF 50% 50% SCREEN MENU PERSIST/OFF DISP ERASE/0.2 s ON DOT
SYNC ANG
Table 4-15.
1 4
RPM
SPECIAL MENU MiniMite and Spitfire Scanners SCAN RPM/1500 R/A 19 Scanner SCAN RPM/1200 0
(Titanium) Filter Settings vs. Hole Diameter
Probe Diameter 5/32″-7/32″ /0.156>7/32″-5/16″ >5/16″-7/16″ 0.219″ /0.219-0.312″ /0.312-0.437″ LPF 500 500 700 HPF 150 200 300 NOTE: Filters may be adjusted +/-50Hz to improve symmetry of notch response. Filter
Description/Setting SETUP MENU FREQ/SINGLE PRB DRV/MID
>7/16″-3/4″ /0.437-0.750″ 1500 500
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T.O. 33B-1-2 4.1.3.8.2 Standardization for Rotary Fastener Hole Inspection of Titanium Parts. NOTE This procedure was developed using a differential/reflection, fastener hole probe, 500KHz-2MHz. The differential/reflection coil design will portray a negative and positive (figure eight) signal response on the impedance plane display. a. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probe should fit snug in the hole without binding. Verify the coil is 90° away from the corner notch and away from hole edges and press NULL. Hold the probe still until nulling is complete. b. Remove the probe from the hole. With the SWEEP turned OFF, hold the scanner so that the probe is parallel to the surface of the reference standard. Place the coil in contact with a flat area of the reference standard at least 1/4 inch away from any edge or notch. Turn the scanner on while the coil makes contact with the reference standard to generate a liftoff signal. c. Adjust the phase rotation by pressing the ANGLE key and rotating the Smartknob to achieve a substantially horizontal liftoff signal. NOTE Titanium will exhibit very little phase separation between the lift-off and defect responses. d. Turn the scanner on and insert the rotating probe into the appropriate hole size in the reference standard and locate the 0.030 inch corner notch located at the interface of the first and second layers. e. Adjust the GAIN to place the entire notch response on the screen. f. Adjust the PHASE until the notch response is at a 45 degree angle from the top left corner of the display down to the bottom right corner of the display. (See Figure 4-35) g. Return to the DISPLAY menu. Press the SWEEP key twice to enter the ‘‘SWEEP EXTRN’’ mode. The instrument is now in sweep mode. h. If the sweep signal is centered at 50% FSH, proceed to step k.
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T.O. 33B-1-2
Figure 4-35.
Response from 0.030 Inch Interface Notch with Phase at a 45 Degree Angle
Figure 4-36.
Example of Properly Calibrated Sweep Display (Titanium)
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T.O. 33B-1-2
Figure 4-37.
Example of Acceptable Noise Level from Clean Hole. Noise Level Shall Not Exceed 10% FSH from Baseline
Figure 4-38.
Display of Signal from Hole That is Subject to Evaluation (Titanium)
i. With the scanner turned off, insert the probe into the appropriate size hole in the reference standard. The probe should fit snug in the hole while rotating freely without binding. Verify the coil is 90º away from the notches and away from hole edges and press NULL. Hold the probe still until nulling is complete.
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T.O. 33B-1-2 j. Remove the probe from the hole. k. Turn the scanner on and reinsert into the reference standard hole. Maximize the signal from the 0.030 inch interface notch. Push the GAIN button and adjust the GAIN (both horizontal and vertical gains will be adjusted simultaneously) as necessary to obtain an 80% Peak-to-Peak (PTP) signal from the notch. The notch signal should appear narrow and nearly symmetric above and below the baseline as shown in Figure 4-36. l. Ensure the signal response from good areas of the hole is relatively smooth across the sweep display. Noise level in good areas shall be no more than 10% negative or positive from the baseline. See Figure 4-37. m. If the noise level is 10% or less from the baseline, proceed to paragraph 4.1.3.8.3. n. If noise signals greater than 10% from the baseline appear, repeat standardization per paragraph 4.1.3.8.2. If the noise level remains excessive after repeated standardization, perform the following steps: (1) Recheck probe fit. (2) Remove probe from scanner and check for inherent scanner and cable noise. (3) Replace the probe, cable or scanner that is causing the noise and repeat standardization per paragraph 4.1.3.8.2. 4.1.3.8.3 Determining Maximum Index Speed. a. Insert the probe into the appropriate hole in the reference standard and locate the 0.030 inch notch at the interface of the first and second layers. b. Monitor the display while moving the probe in and out over the interface notch. NOTE The maximum speed that the probe can be moved through the hole is the rate of probe travel that always identifies the notch and does not cause a reduction the peak in signal height from 80% FSH PTP. c. Gradually increase the probe travel speed until the peak height of the notch response begins to decrease below 80% FSH PTP. This is the maximum probe travel speed. 4.1.3.8.4 Identifying the Scanner Zero or Scan Origin. Establish the scanner zero or scan origin by using one of the following methods: 4.1.3.8.4.1 Method A: Setting the scanner Sync Zero position. a. Visually locate the notch on the top surface of the reference standard. b. Insert the probe into the appropriate hole in the reference standard and rotate the scanner housing until the red LED alarm indicator on the side of the scanner housing is pointed at the physical position of the notch on the standard as shown in (See Figure 4-39 and Figure 4-40). c. Turn on the scanner and adjust the SYNC ANGLE in the SPECIAL menu screen until the trailing edge of the notch indication is displayed on the left side of the screen with the leading edge of the indication positioned on the right side of the screen (split-signal) as shown in (see Figure 4-39). NOTE An acceptable alternate approach is to place the notch signal in the center of the screen and use this position as the scanner zero. 4.1.3.8.4.2 Method B: Locating Sweep Crossing for Scanner/Notch Alignment. a. Visually locate the notch on the top surface of the reference standard. b. Insert the rotating probe into the appropriate hole in the reference standard until the maximum signal is obtained from the notch.
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T.O. 33B-1-2 c. Rotate the scanner until the top, center of the scanner is in line with the notch. d. Note the point at the center of the notch signal crosses the sweep baseline. This is scanner zero as shown in Figure 4-41. e. Locate crack position by rotating the scanner until crack signal appears at the scanner zero location. Crack will be in line with the top, center of the scanner.
Figure 4-39.
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Establishing SYNC Zero Position of the Nortec Spitfire Scanner (Titanium)
T.O. 33B-1-2
Figure 4-40.
Establishing SYNC Zero Position of the Nortec MiniMite Scanner (Titanium)
Figure 4-41.
Establishing SYNC Zero Position of the Nortec Spitfire Scanner (Method C)
4.1.3.8.5 Alarm Setting. Alarm use is optional. Refer to the operator manual or part specific procedures for alarm setting instructions.
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T.O. 33B-1-2 4.1.3.8.6 Inspection. NOTE • Standardization of the unit should be verified at least once every 10 minutes or every 30 holes, whichever comes first. If the interface notch signal does not provide the required 70-90% vertical PTP deflection then repeat standardization and inspection of all holes done since the last good calibration check. • The surface condition of the hole can affect the inspection result. This procedure assumes that the bore is essentially round and smooth. The hole is considered uninspectable if the general surface condition causes noise signals greater than 10% from the baseline during scanning. Application of Teflon tape over the probe coils may help reduce excessive noise. a. Visually verify the hole surface condition will not damage the probe during inspection and is void of any foreign material (e.g. grease, sealant, metal shavings). b. Enter data available to this point on an inspection record, if required. Enter additional data in record as it is obtained. c. With the scanner off, check probe fit in the holes to be inspected. The fit should approximate the fit in the reference standard. Remove the probe from the hole. d. Turn on the scanner and reinsert the probe in the hole. Inspect by slowly pushing the probe through the entire hole then pulling the probe slowly back through the hole. The probe must be kept perpendicular to the part surface during scanning. The hole is considered uninspectable if the general surface condition causes noise signals than 10% above or below the baseline on the sweep display (see Figure 4-37) Additional hole preparation and cleaning may be required prior to reinspection. Repeat a minimum of twice for each hole to be inspected. 4.1.3.8.7 Indication Evaluation, Marking, and Recording. 4.1.3.8.7.1 Any repeatable indication above the background noise, exhibits a vertical response greater than 30% vertical PTP (See Figure 4-38) and appears similar to that obtained from the reference standard shall be considered a possible crack. a. Using an approved marker, mark all repeatable crack-like indications. b. Verify the instrument standardization after the detection of a crack indication by performing a sensitivity check of the unit as follows: (1) Insert the probe into the appropriate reference standard hole and maximize the signal response received from the reference notch. (2) The notch signal should exhibit a vertical signal within 70% - 90% PTP. If it does then the defect indication SHALL be considered valid and recorded. (3) If the notch signal does not provide the required 70% - 90% vertical PTP deflection then repeat the standardization in accordance with paragraph 4.1.3.8.2 and repeat the inspection. 4.1.3.8.8 Identifying the Circumferential Location of an Indication. a. Maximize the indication response. b. Identify the radial location by rotating the scanner to bring the displayed indication to the sweep line zero position (left side of screen). c. Using an approved marker, place a mark on the part surface in line with the scanner zero point that was identified in paragraph 4.1.3.5.4. 4.1.3.8.9 Identifying the Length of a Crack-Like Indication Down the Bore of a Hole (If Required). a. Without covering the face of the probe, wrap the probe shaft with a piece of masking tape. b. Hold an approved fine-tipped marker parallel to the part surface with the marking point pointing toward the probe shaft.
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T.O. 33B-1-2 c. Insert the probe into the hole containing the crack-like indication. d. As the probe is scanned through the hole use the marker to make a mark on the masking tape when the crack indication first reaches 30% FSH PTP. e. Continue to scan in the hole. Use the marker to make a second mark on the masking tape when the indication height drops back to 30% FSH PTP. f. Determine the indication length by measuring the distance between the marks on the masking tape. Use a ruler with the appropriate scale. 4.1.3.8.10 Backup Procedure. If the part specific procedure does not specify a backup procedure it is recommended that the indication be verified by a second inspector. Repeat standardization per paragraph 4.1.3.8.2 and have a second inspector verify the indication. If available, separate equipment and probes should also be used for each independent inspection. If the defect indication is not confirmed, proceed to system securing.
4-55
T.O. 33B-1-2
SECTION II EDDY CURRENT PROCESS CONTROL PROCEDURES 4.2
EDDY CURRENT PROCESS CONTROL PROCEDURES.
4.2.1 General Process Control for Eddy Current Inspection Probes and Standards. For maximum reliability in ET, a high signal-to-noise ratio is desired. No specific signal-to-noise ratio is mandatory, but a minimum of 3-to-1 is desirable for flaw detection. 4.2.2 Probe Test. The following steps are designed for testing in-use surface eddy current probes 1/8-inch or smaller: a. Attach probe and cable to the proper connector. b. Place Teflon tape across the four surface slots on the Air Force general purpose eddy current standard. c. Turn on the unit by pressing the green circular button. When the unit is first turned on it will display the ‘‘DIAGNOSTICS’’ self-test and the last setup program that was used. NOTE Step d - step j loads the ‘‘DEFAULT’’ program. d. Press the [SETUP/SPECIAL] button until the ‘‘set up’’ menu appears. The ‘‘setup’’ menu displays REPORT CLOCK DEFAULT in the top row. e. Press the 3rd soft key [
] until DEFAULT is highlighted.
f. Press the [ENTER] button. g. Press the 4th soft key [ ] to select LD DEFLT. There should be 3 highlighted areas: LD DEFLT lower right side above the 4th soft key [ ], LD DEFLT 4th row in right column, and DEFAULT above 5th soft key [ ]. h. Press the [ENTER] button. NOTE A 4th highlighted LD DEFLT will be displayed above the function row. To the right of the highlighted LD DEFLT there will be either CANCEL or CONFIRM. i. Rotate the SMARTKNOB until it reads CONFIRM. j. Press the [ENTER] button. NOTE The ‘‘DEFAULT’’ program is now loaded. The MAIN menu display should be in ‘‘flying dot’’ mode. The following values should be displayed. FREQUENCY 100 kHz ANGLE 0° H-GAIN 40.0 dB V-GAIN 40.0 dB PROBE DRIVE MID k. FREQUENCY should be highlighted; if not, press 1st soft key [
].
l. Rotate SMARTKNOB to set the minimum frequency identified on the probe. m. Press the 3rd soft key [
4-56
].
T.O. 33B-1-2
NOTE GAIN should be highlighted above the soft key and both the H-GAIN and V-GAIN should be highlighted on the right side. n. Rotate the SMARTKNOB to set the gain at 50 dB horizontal and 50 dB vertical. o. Place the probe on the Teflon tape away from slot and ‘‘null’’ the instrument by pressing the [NULL] button. p. Press the [ERASE] button. NOTE After ‘‘nulling’’ the instrument it is always a good practice to press the [ERASE] button after pressing the [NULL]button. This clears the display and places the ‘‘flying dot’’ at the center position. q. Press the 2nd soft key [
]. ANGLE should be highlighted in two places.
r. Scan over the 0.050 inch slot while rotating the SMARTKNOB to adjust phase angle. The ‘‘flying dot’’ should be rotated to a vertical position. s. Press the 3rd soft key [
]. (See step m note)
t. While scanning the 0.050 inch slot, rotate the SMARTKNOB until the response from the crack moves the dot exactly three square divisions. To improve gain control use the [ERASE] button occasionally to clear the display. u. Record the gain setting for that frequency. v. Repeat the step k through step u to achieve a low, medium (pick a number that is between the low and high), and high frequency reading for each probe. {e.g., 60.3 at 50 kHz for a low frequency. 53.2 at 200 kHz and 59.6 at 500 kHz} NOTE Some probes have their frequency range (low to high frequencies) identified on the probe handle. Others may not. If the probe frequency range is not identified, use 200 kHz, 500 kHz, or 1 MHz. The “flying dot” will not behave properly when the probe’s frequency range is exceeded (either low or high). The dot should be relatively stable after “nulling” the instrument. There should be a definite response displayed when the 0.050 inch slot is scanned. If not, try another frequency. The optimum frequency for the probe is the frequency with the lowest gain setting and highest signal response. Probes shall be tested after receiving them and periodically thereafter. If the gain settings are off by 20 percent or more the next time you test the probe, it should be replaced. 4.2.3 Slot Test. Attach probe and cable to the proper connector. a. Place Teflon tape across the four surface slots on the Air Force general purpose eddy current standard. b. Turn on the unit by pressing the green circular button. When the unit is first turned on it will display the ‘‘DIAGNOSTICS’’ self test and the last setup program that was used. NOTE Step c - i loads the ‘‘DEFAULT’’ program. c. Press the [SETUP/SPECIAL] button until the ‘‘set-up’’ menu appears. The ‘‘setup’’ menu displays REPORT CLOCK DEFAULT in the top row. d. Press the 3rd soft key [
] until DEFAULT is highlighted.
4-57
T.O. 33B-1-2 e. Press the [ENTER] button. f. Press the 4th soft key [ ] to select LD DEFLT. There should be 3 highlighted areas: LD DEFLT lower right side above the 4th soft key [ ], LD DEFLT 4th row in right column, and DEFAULT above 5th soft key [ ]. g. Press the [ENTER] button. NOTE A 4th highlighted LD DEFLT will be displayed above the function row. To the right of the highlighted LD DEFLT there will be either CANCEL or CONFIRM. h. Rotate the SMARTKNOB till it reads CONFIRM. i. Press the [ENTER] button. NOTE The ‘‘DEFAULT’’ program is now loaded. The MAIN menu display should be in ‘‘flying dot’’ mode. The following values should be displayed. FREQUENCY 100 kHz ANGLE 0° H-GAIN 40.0 dB V-GAIN 40.0 dB PROBE DRIVE MID j. FREQUENCY should be highlighted; if not, press 1st soft key [
].
k. Rotate SMARTKNOB to set the frequency at 500 kHz. l. Press the 3rd soft key [
]. NOTE
GAIN should be highlighted above the soft key and both the H-GAIN and V-GAIN should be highlighted on the right side. m. Rotate the SMARTKNOB to set the gain at 50 dB horizontal and 50 dB vertical. n. Place the probe on the Teflon tape away from slot and ‘‘null’’ the instrument by pressing the [NULL] button. o. Press the [ERASE] button. NOTE After ‘‘nulling’’ the instrument it is always a good practice to press the [ERASE] button after pressing the [NULL]button. This clears the display and places the flying dot at the center position. p. Press the 2nd soft key [
]. ANGLE should be highlighted in two places.
q. Scan over the 0.050 inch slot while rotating the SMARTKNOB to adjust phase angle. The ‘‘flying dot’’ should be rotated to a vertical position. r. Press the 3rd soft key [
]. (See paragraph 4.2.3, step n note)
s. While scanning the 0.050 inch slot, rotate the SMARTKNOB until the response from the crack moves the dot exactly three square divisions. To improve gain control, use the [ERASE] button occasionally to clear the display.
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T.O. 33B-1-2 t. Place a straight edge (ruler, triangle edge, etc) adjacent to and inline with the notch so that the probe’s center is on the center of the notch. u. Press the [ERASE] button so that the dot is showing at three divisions. v. Move the probe down the slot lengthwise using the straight edge as a guide. w. The dot should not move more than 1/10th of a division until it comes to the edge of the standard or the edge of the slot (Edge Effect). x. Repeat the step m through step u (see paragraph 4.2.3) for the 0.020, 0.010, and 0.005 slots. Remember the gain will have to be increased to align the dot at three divisions. NOTE For the 0.005″slot, use one division instead of three divisions. The aluminium general purpose eddy current standard SHALL be tested whenever the slots appear to be worn.
4-59/(4-60 blank)
T.O. 33B-1-2
CHAPTER 5 ULTRASONIC INSPECTION SECTION I ULTRASONIC INSPECTION GENERAL PROCEDURE
(NOT APPLICABLE)
5-1
T.O. 33B-1-2
SECTION II ULTRASONIC INSPECTION PROCESS CONTROL 5.1
ULTRASONIC INSPECTION PROCESS CONTROL. NOTE Ultrasonic process control checks are intended for general purpose transducers and centrally procured ultrasonic instruments. Manufactures’ recommended process control checks SHOULD be used for special purpose transducers and ultrasonic instruments. For guidance contact the appropriate ALC NDI Manager. Table 5-1.
Basic Gain: 40 dB starting point Range: 10.00 MTL Vel: Refer to Auto-Cal Delay: 0.00 Gate A-THRSH: 10% A-Start: 2.500 A-Width: 0.750
Vertical Linearity
ASTM Block Vertical Linearity Receiver Gain: 40 dB starting point Frequency: Select Best Damping: 50 Rectif: Full
Pulser Gain: 40 dB starting point Pulser: Single Reject: 0 Rep-Rate: High
Leave remaining function keys set as they are Calibration Procedures paragraph 5.1.1 1) 2) 3) 4)
Utilize three blocks with 3/64, 5/64, and 8/64 FBH with 3″ metal travel distance Place the transducer on the 5/64 FBH block and set to 35% amplitude Go to the 3/64 FBH and the amplitude should be 10-16% Then go to the 8/64 FBH and the amplitude should be 85-95%
5.1.1 Procedure for Determining Vertical Linearity Limits (ASTM Blocks). a. (Table 5-1) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Use three ASTM blocks with 3-inch metal travel distances, one each with a 3/64, 5/64, and 8/64-inch diameter flatbottom hole (FBH). c. Move the search unit over the surface of the 5/64-inch FBH block until a maximum response is obtained from the FBH. Make sure that the reject control and filters are in the ‘‘off’’ or minimum positions. Adjust the instrument gain control until the FBH signal is 35-percent of vertical screen height on the CRT. d. Leave the gain fixed, maximize the FBH signal on the 3/64 and 8/64 FBH blocks. Record the FBH signal amplitudes. e. If the instrument is linear, the signals from the 3/64 and 8/64 FBH’s will be 13% ±3% and 90% ±5% of saturation respectively. Thus, a 3/64 FBH signal between 10% and 16% of saturation is considered linear; an 8/64 FBH signal between 85% and 95% of saturation is considered linear. f. Instruments not linear (within the above limits) SHALL be repaired or replaced.
5-2
T.O. 33B-1-2 5.1.2 Procedure for Determining Horizontal Linearity Limits (Type 2 IIW Block). In lieu of any specific linearity requirement, the horizontal linearity MAY be checked as follows: a. Table (5-2) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Use the IIW block and a straight beam transducer (see Figure 5-1).
Figure 5-1.
Use the Type 2 IIW Block to Check Horizontal Linearity
c. Place the transducer on the IIW block and adjust the gain so that the first back reflection achieves 95% full screen height and the range to obtain six back reflections on the display screen. The first back reflection SHOULD be located at the left side of the base line (the initial pulse SHOULD be off the screen), and the 6th back reflection SHOULD be located at the right side of the base line. d. Measure the distance between the leading edge of adjacent back reflections. Ideal horizontal linearity will be indicated by an equal distance between the leading edges of subsequent back reflections. If all the values are equal within 3.0% of the full scale width, the instrument is considered linear in the horizontal direction. e. Instruments not linear within the above limits SHALL be repaired or replaced. Table 5-2.
Horizontal Linearity
Horizontal Linearity (IIW) Basic Gain: 30 dB Range: 10.00 MTL Vel: Refer to AutoCal Delay: 0.000 Gate Gain: 30 dB
Receiver Gain: 30 dB Frequency: 2-8 Damping: 50
Pulser Gain: 30 dB Pulser: Single Reject: 0
Rectif: Full
Rep-Rate: High
5-3
T.O. 33B-1-2 Table 5-2.
Horizontal Linearity - Continued
Horizontal Linearity (IIW) A-THRSH: 20% A-Start: Move as needed A-Width: 1.000 Leave remaining function keys set as they are
Calibration Procedures paragraph 5.1.2 1) Lay IIW block flat 2) Place the transducer on standard; the indication should go thru gate 3) Use the delay function to move IP off screen and the first back reflection to the IP position (zero on the horizontal zero/trace line) 4) Adjust the gain to get 6 indications 5) Use the ‘‘A-START’’ key to read the distance for each indication. They should be 1″ apart. Note: The ‘‘B’’ gate may be used for measurement between multiples
5.1.3 Procedure for Determining Inspection System Sensitivity (ASTM Blocks). NOTE • The 1 MHz and 15 MHz requirements are applicable only when these frequencies are to be used; they are not specific requirements for all instruments. • Unless otherwise specified in a detailed procedure, use the ASTM reference blocks with flatbottom holes (FBH). The FBH, which SHOULD be detectable with the respective frequencies, are shown in (see Table 5-3). a. (Table 5-1) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Select the ASTM block with the appropriate FBH at a depth of 3-inches. (Table 5-3) shows compensation values. When the 3/64 FBH and the 5/64 FBH are used in place of the 2/64 and 4/64 respectively. For example: When using the 3/64 FBH instead of the 2/64, the equipment gain must be increased 7dB to obtain the same inspection sensitivity. The increase in gain will cause the signal height to exceed 60-percent screen height. c. Obtain a peak signal from the appropriate FBH. Table 5-3. Frequency (MHz) FBH Size (inch/64) dB Compensation
Minimum Sensitivity Requirements 1 8 N/A
2.25 5 +4
2.25 4 N/A
5 3 +7
5 2 N/A
d. Adjust the Gain control of the instrument until the discontinuity indication is 60-percent of full screen height. 5-4
T.O. 33B-1-2 e. Notice the baseline noise in the test region (adjacent to the FBH indication). The noise SHOULD be no higher than 20-percent of full screen height. The noise threshold does not change when using ASTM blocks requiring additional gain. f. When a reference standard, specified by a detailed inspection procedure, is used the minimum signal-to-noise ratio is also 3 to 1. g. If the inspection system does not meet these sensitivity requirements, the transducer and/or cable SHALL be replaced and the sensitivity checked again. If the inspection system still does not meet the above requirements, the instrument SHALL be repaired or replaced. 5.1.4 Checking Resolution (Type 2 IIW Block). When no resolution is specified, the following procedures is used to check resolution: 5.1.4.1 Back Surface Resolution (Figure 5-2)(2.25 MHz only). a. (See Table 5-4) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Position the transducer on a Type 2 IIW block, and peak the signal from reflector A. c. Maximize the separation of the signals from the reflectors A, B, and C. d. Evaluate the resolution by matching the signal patterns. Good resolution is indicated by the respective signals returning to the baseline. e. If a test system with a 2.25 MHz search unit does not meet these resolution requirements, the transducer and/or cable SHALL be replaced and the resolution checked again. If the inspection system still does not meet the above requirements, the instrument SHALL be repaired or replaced.
Figure 5-2.
Use Type 2 IIW Block to Check Back Surface Resolution
Table 5-4.
Basic Gain: 30 dB starting point Range: 5.00 MTL Vel: Refer to Auto-Cal
Resolution Set-up
Resolution (Back Surface) IIW Receiver Gain: 30 dB starting point Frequency: 2-8 Damping: 50
Pulser Gain: 30 dB starting point Pulser: Single Reject: 0 5-5
T.O. 33B-1-2 Table 5-4.
Delay: 0.000
Resolution Set-up - Continued
Resolution (Back Surface) IIW Rectif: Full
Rep-Rate: High
Gate Gain: 30 dB starting point A-THRSH: 20% A-Start: Move as needed A-Width: 1.000 Leave remaining function keys set as they are Calibration Procedures paragraph 5.1.4 1) Refer to Figure 5-2 5.1.4.2 Entry Surface Resolution (Dead Zone) (Type 2 IIW Block). a. (See Table 5-4) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Position the transducer on an IIW block at P-1 or P-2 as shown in (see Figure 5-3). P-1 gives 0.2-inch metal travel distance to the edge of the large hole. P-2 gives 0.4-inch metal travel distance. c. Maximize the separation between the initial pulse and the hole signal. Evaluate the signal pattern according to the criteria given in (see Figure 5-3). d. Check that the signal of the hole is actually the indication of the first echo from the hole by noting the position of the hole signal on the calibrated distance scale of the waveform display. The distance SHOULD be the actual depth of the hole. e. The first echo from the edge of the hole SHALL be completely separate from the initial pulse. The initial pulse SHALL return to the baseline, as shown in the ‘‘good’’ example of (see Figure 5-3), for the following conditions: • • •
10 MHz: Good at P-1 and P-2. 5 MHz: Good at P-2. 2.25 MHz: Good at P-2.
f. If the first echo from the edge of the hole is not completely separate from the initial pulse as required above, the transducer and/or cable SHALL be replaced and the dead zone checked again. If the inspection system still does not meet the above requirements, the instrument SHALL be repaired or replaced.
5-6
T.O. 33B-1-2
Figure 5-3.
Use a Type 2 IIW Block to Check Entry Surface Resolution
Table 5-5.
Basic Gain: 30 dB starting point Range: 2.500 MTL Vel: Refer to Auto-Cal Delay: 0.00 Gate Gain: 30 dB starting point A-THRSH: 20% A-Start: 0.200 A-Width: 0.200
Dead Zone Set-up
ASTM Block Dead Zone (Entry Surface Resolution) Receiver Pulser Gain: 30 dB starting point Gain: 30 dB starting point Frequency: 2-8 Pulser: Single Damping: 50 Reject: 0 Rectif: Full Rep-Rate: High
Leave remaining function keys set as they are Calibration Procedures paragraph 5.1.4.3 1) Pick the block that matches the frequency of transducer you are using (see Table 5-6) 2) Place transducer on the block over the flat bottom hole (FBH) 3) Look for the FBH signal between the initial pulse (IP) and back reflection (BR). The FBH should be complete and separate indication. (See Figure 5-3) 4) Adjust the gain to get 6 indications 5) Use the ‘‘A-START’’ key to read the distance for each indication. They should be 1″ apart. Note: The ‘‘B’’ gate may be used for measurement between multiples
5-7
T.O. 33B-1-2
Table 5-6.
Limits of Boundary Surface Resolution
Frequency (MHz) Entry Surface Resolution in Aluminum (inch) Back Surface Resolution in Aluminum (inch)
1 0.5 0.5
2.25 0.375 0.3
5 0.25 0.2
10 0.125 0.1
15 0.125 0.1
5.1.4.3 Entry Surface Resolution (ASTM Blocks). a. (See Table 5-5) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Use an ASTM block with a #5 FBH or other size if specified. Choose a block with a metal travel distance according to the frequency being used (see Table 5-6). c. Maximize the separation between the initial pulse and the signal from the hole. d. Check that the signal from the hole is actually the indication of the first echo from the hole by noting the position of the signal from the hole on the calibrated distance scale of the waveform display. The distance SHOULD be the actual depth of the hole. e. Evaluate the waveform patterns. 5.1.5 A-Scan Straight Beam Distance Calibration.
Table 5-7.
1) 2) 3) 4)
5-8
Auto Calibration Procedures
AUTO CAL PROCEDURES:ASTM BLOCKS COLD BOOT UNIT SELECT LOWER LEVEL MENU WITH WHITE UP/DOWN ARROW TOGGLE THRU LOWER LEVEL MENU UNTIL YOU SEE THE AUTO CAL COLUMN SELECT: A. Auto-Cal: On B. Gate Logic: Positive C. Measure: 0-1st D. TOF: Flank INSTRUMENT SETTINGS BASIC RECEIVER PULSER Gain: 30 dB Gain: 30 dB Gain: 30 dB Range: 5.000 Frequency: 2-8 MHz Pulser: Single Mtl-Vel: (self-adjust) Damping: 50 Reject: 0 Delay: 0.000 Rectif: Full Rep-Rate: High GATE S-CAL MEM Gain: 30 dB Gain: 30 dB Gain: 30 dB A-Thrsh: 20% Cal: Recall: Off A-Start: 0.700 A-Start: 0.700 Set:#1 A-Width: 4.500 S-Ref: 1.000 Store: Off TCG Gain: 30 dB DAC/TCG: Off
T.O. 33B-1-2 Table 5-7.
Auto Calibration Procedures - Continued
AUTO CAL PROCEDURES:ASTM BLOCKS A-Start: 0.700 DAC Echo: 0 6) 7) 8) 9) 10) 11) 12) 13)
Select S-Cal menu Press Cal left/right key simultaneously, ″REC 0″ will appear Confirm S-Ref thickness is one inches (1.0″) and select your 0025 ASTM Block Place transducer on standard, ensure that the back reflection goes thru gate by adjusting gain and move probe as needed to maximize signal. Press the right arrow key next to cal, ″REC 0″ will change to ″REC 1″ and S-Ref will change to 4.000 inches Adjust S-Ref thickness to 3.75″ and select 0300 ASTM block Place transducer on standard again, ensuring that back reflection passes thru gate, adjust gain as needed. Press the right key next to Cal twice, and the unit will calculate the material velocity, and zero, probe delay (record settings for future use)
5.1.5.1 Straight Beam Distance Calibration (Type 2 IIW Block). a. (See Table 5-7) contains the set-up for the USN-52 ultrasonic unit using the ASTM blocks. Adjust the range to accommodate the IIW block; the instrument may need to be adjusted to obtain the required screen presentation. b. Position the search unit on an IIW block at P-1, P-2 or P-3 as shown in (see Figure 5-4). The distance between multiple back reflections is as follows: • • •
1.00 inch at P-1. 4.00 inch at P-2. 8.00 inch at P-3.
c. Set the time base for the applicable distance calibration. Example: see display screens for various distance calibrations are shown in (see Figure 5-4).
5-9
T.O. 33B-1-2
Figure 5-4.
Straight Beam Distance Calibration with IIW Block
Table 5-8.
Basic Gain: 30 dB starting point Range: 5.00 MTL Vel: Refer to Auto-Cal Delay: 0.00 Gate Gain: 30 dB starting point A-THRSH: 20% A-Start: Move as needed A-Width: 1.000
Straight Beam Distance
ASTM Block Straight Beam Distance Calibration Receiver Pulser Gain: 30 dB starting point Gain: 30 dB starting point Frequency: 2-8 Pulser: Single Damping: 50 Reject: 0 Rectif: Full Rep-Rate: High
Leave remaining function keys set as they are Calibration Procedures paragraph 5.1.5.3
5-10
T.O. 33B-1-2 Table 5-8.
1) 2) 3) 4)
Straight Beam Distance - Continued
ASTM Block Straight Beam Distance Calibration Select the 7075-05-0025 block IP=0 BR=1.0 Look at multiples and count. You should have a multiple every 1.0″ Adjust the gain until you have four indications from back wall. Move A-START to read each distance
5.1.5.2 Straight Beam Distance Calibration (Miniature Angle Beam Block). a. (See Table 5-7 or Table 5-8) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Position the transducer on the miniature block at P-1 or P-2 as shown in (see Figure 5-5). The distance between multiple back reflections is as follows: c. Set the time base for the applicable distance calibration. • •
0.250 inch at P-1. 1.000 inch at P-2.
Figure 5-5.
Straight Beam Distance with Miniature Angle Beam Block
5.1.5.3 Straight Beam Distance Calibration (ASTM Blocks). (See Table 5-7) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. 5.1.5.3.1 Distance calibration MAY be performed using multiple reflections from the FBH or the back surfaces of ASTM blocks. The procedures are identical to the procedures outlined above using the Type 2 IIW block and the miniature angle beam block. 5.1.6 Angle Beam Distance Calibration (Type 2 IIW Block). NOTE This procedure works with all commonly used angles. a. (See Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Position the transducer at P-1 (see Figure 5-6) and adjust the location of the transducer to be directed at radius R-2. Peak the signal from radius R-2 by sliding the transducer toward and away from R-2 until the signal reaches maximum amplitude. Use DELAY control to position the peaked signal to the appropriate location on the horizontal baseline. Using the RANGE control, repeat these steps until the peaked signals from R-2 and R-4 are located at the required positions on the baseline. Repeat these steps until the peaked signals from R-2 and R-4 are located at the required positions on the baseline.
5-11
T.O. 33B-1-2 c. This method works for 45 degree transducers only: position the transducer along scale ‘‘C’’ and obtain a peak signal from the hole as shown in (see Figure 5-6). Distance is read directly off the scale. P-2 shows 2.5-inches; P-3 shows 5-inches. Table 5-9.
Auto Calibration Procedures
AUTO CAL PROCEDURES:ANGLE BEAM TESTING I/W 1) 2) 3) 4)
5)
COLD BOOT UNIT SELECT LOWER LEVEL MENU WITH WHITE UP/DOWN ARROW TOGGLE THRU LOWER LEVEL MENU UNTIL YOU SEE THE AUTO CAL COLUMN SELECT: A. Auto-Cal: On B. Gate Logic: Positive C. Measure: 0-1st D. TOF: Flank THEN TOGGLE TO ANGLE COLUMN: A. Angle: 45.0 B. Thickness: 4.000 in. C. X-Value: 0.563 D. O-Diam: Infinity
BASIC Gain: 40 dB Range: 5.000 Mtl-Vel: 0.1320 Delay: 0.000 GATE Gain: 40 dB A-Thrsh: 20% A-Start: 1.000 A-Width: 3.750
6) 7) 8) 9) 10) 11) 12) 13)
5-12
INSTRUMENT SETTINGS RECEIVER Gain: 40 dB Frequency: 2-8 MHz Damping: 50 Rectif: Full S-CAL Gain: 40 dB Cal: A-Start: 1.000 S-Ref: 2.000 TCG Gain: 40 dB DAC/TCG: Off A-Start: 1.000 DAC Echo: 0
PULSER Gain: 40 dB Pulser: Single Reject: 0 Rep-Rate: High MEM Gain: 40 dB Recall: Off Set:#1 Store: Off
Select S-Cal menu Press Cal left/right key simultaneously, ″REC 0″ will appear. Confirm S-Ref thickness is two inches (2.0″) and select IIW standard. Place transducer on standard as shown in (Figure 5-6) to pick up 2-inch reflector. Ensure the back reflection goes thru the gate by adjusting the gain. Press the right arrow key next to cal, ″REC 0″ will change to ″REC 1″ and S-Ref will change to 4.000 inches Confirm S-Ref thickness is 4-inches (4.0″). Place transducer on standard again, ensuring that back reflection passes thru gate, adjust gain as needed. Press the right key next to Cal twice, and the unit will calculate the material velocity, and zero, probe delay (record settings for future use).
T.O. 33B-1-2
Figure 5-6.
Angle Beam Distance Calibration with IIW Block
Table 5-10.
Angle Beam Distance Calibration
Angle Beam Distance Calibration IIW Calibration Procedures paragraph 5.1.6 1) Leave function keys set as they are from auto calibration procedures, confirm distance calibration. 2) NOTE: Use position P-1 to show amplitude signals from R-2, and R-4 only. Always expect a high P-Delay due to lucite wedge. Angle Beam Point of Incidence IIW Calibration Procedures paragraph 5.1.7 1) Leave function keys set as they are from auto calibration procedures, and follow procedures to mark point of incidence. Angle Beam Angle Determination IIW Calibration Procedures paragraph 5.1.8
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T.O. 33B-1-2 Table 5-10.
Angle Beam Distance Calibration - Continued
1) Leave function keys set as they are from auto calibration procedures, and confirm angle beam angle determination. 5.1.6.1 Angle Beam Distance Calibration (Miniature Angle Beam Block). This procedure works with angles over 45 degrees. a. (See Table 5-9 and Table 5-10) contains the set-up for the USN-52 ultrasonic unit; the instrument may need to be adjusted to obtain the required screen presentation. b. Position the transducer at P-1 and then P-2 as shown in (see Figure 5-7). Obtain peak signals from R-1 and then from R-2. CAUTION Ensure you are using the proper transducer and standard matched for the material you wish to inspect. c. The angle beam metal travel at P-1 is 1-inch; at P-2, it is 2-inches.
Figure 5-7.
Angle Beam Distance Calibration with Miniature Angle Beam Block
5.1.7 Angle Beam Point-of-Incidence (Type 2 IIW Block). The point-of-incidence is defined as the center point of the sound beam exiting the transducer wedge. It is usually indicated by a mark on the side of the wedge at the point where an imaginary line through the exit point of the beam intersects the side of the wedge. a. (See Table 5-9 and Table 5-10) contains the set-up for the USN-52 ultrasonic unit; the instrument may need to be adjusted to obtain the required screen presentation.
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T.O. 33B-1-2 b. Move the transducer back and forth from the curved surface at R-4 (see Figure 5-8) until the peak signal from R-4 is obtained. c. The transducer point-of-incidence now coincides with the line marked ‘‘0’’ on the block. Mark the point-ofincidence on the side of the search unit. NOTE Marking (etching) by mechanical means MAY damage the sensitive transducer.
Figure 5-8.
Point of Incidence Determination with IIW Block
5.1.7.1 Angle Beam Point of Incidence (Miniature Angle Beam Block). NOTE The point-of-incidence as determined in accordance with these procedures MAY NOT correspond with the pointof-incidence placed on the transducer by the transducer manufacturer. Once the point-of-incidence is located and marked on the transducer, distance determinations shall be done using reference blocks made of the same material as that to be inspected, or a material of approximately the same shear wave velocity if the same material is not available. For example, if inspecting titanium, an aluminum block may be used if a titanium reference block is not available. a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Move the transducer back and forth from the curved surface at R-2 (see Figure 5-9) until the peak signal from R-2 is obtained. Once the point-of-incidence is located and marked on the transducer, distance determinations shall be done using reference blocks made of the same material as that to be inspected, or a material of approximately the same shear wave velocity, if the same material is not available. For example, if inspecting titanium, an aluminum block may be used if a titanium reference block is not available. c. The transducer point-of-incidence now coincides with the line marked ‘‘0’’ on the block. Mark the point-ofincidence on the side of the transducer.
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T.O. 33B-1-2
Figure 5-9.
Point of Incidence Determination with Miniature Angle Beam Block
5.1.8 Determining Angle Beam Misalignment (Skew Angle). Skew angle is a measure of the misalignment angle between the ultrasonic beam and the search units’ axis of symmetry (see Figure 5-10). a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit; the instrument may need to be adjusted to obtain the required screen presentation. b. Place the Type 2 IIW block flat on the side and adjust the search unit to maximize the echo from the other corner of the block (see Figure 5-11). The corner of the block where there are no scale engravings SHALL be used. c. Place a protractor on the block, as shown in (see Figure 5-11) and measure the skew angle. The skew angle of new and used ultrasonic transducers SHALL be maintained within 2-degrees of the probe symmetry axis.
Figure 5-10.
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Beam Misalignment (Skew Angle)
T.O. 33B-1-2
Figure 5-11.
Skew Angle Measurement
5.1.9 Angle Beam Angle Determination (Type 2 IIW Block). a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Position the transducer on scale ‘‘A’’ or ‘‘B’’ as shown in (see Figure 5-12). Move the transducer back and forth until the peak signal from the hole is obtained. c. Read the refracted angle from the position on scale ‘‘A’’ or ‘‘B’’ coinciding with the point-of-incidence. In (see Figure 5-12), P-1 shows 60°; and P-2 shows 45°. The refracted angle SHALL be + or - 2-degrees of the original design.
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T.O. 33B-1-2
Figure 5-12.
Angle Determination with Type 2 IIW Block
5.1.9.1 Angle Beam Angle Determination (Miniature Angle Beam Block). a. (Table 5-9) contains the set-up for the USN-52 ultrasonic unit, the instrument may need to be adjusted to obtain the required screen presentation. b. Position the transducer on scale ‘‘A’’ or ‘‘B’’ as shown in (see Figure 5-12). Move the transducer back and forth until the peak signal from the hole is obtained. c. Read the refracted angle from the position on scale ‘‘A’’ or ‘‘B’’ coinciding with the point-of-incidence. (see Figure 5-13) (and P-2 shows 700) d. Angle beam determination can also be done with the miniature angle beam block (see Figure 5-13).
Figure 5-13.
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Angle Determination with Miniature Angle Beam Block
T.O. 33B-1-2
CHAPTER 6 RADIOGRAPHIC INSPECTION SECTION I RADIOGRAPHIC INSPECTION GENERAL PROCEDURE
(NOT APPLICABLE)
6-1
T.O. 33B-1-2
SECTION II RADIOGRAPHIC INSPECTION GENERAL PROCEDURE 6.1
RADIOGRAPHIC INSPECTION PROCESS CONTROL.
6.1.1 Individual Safelight Evaluation Check. a. X-ray a piece of 14x17 Class 4 X-ray film until a 1.5 density is achieved. Note the distance, time, kVp, and mA used. Expose another piece of the same type of film for use in the safelight test and leave unopened until ready to perform the test. (Class 4 = Kodak AA, Fuji IX100, or Agfa D7) b. Turn off, disconnect, or remove all safe lights from the dark room except the one to be tested. c. Turn off remaining safelight and open the exposed 14x17-inch sheet of class 4 film in complete darkness. d. Cover the entire sheet of film with cardboard or other like type of material; place it in the working area at least four feet under the safelight. e. Uncover 2.5-inch section of film, turn on the safelight and expose it to the safelight for 6-minutes. After 6-minutes, uncover another 2.5-inch and expose for 3- minutes. Repeat the procedure for 1-minute, 30 seconds, and 15 seconds. Be sure to leave the last section covered and completely unexposed. f. Turn off safelight and develop the film in complete darkness. g. Take density reading for all the sections on the X-ray film and compare to the last, unexposed section. The section with the least amount of measurable density change is the maximum allowable time undeveloped film may be exposed to this safelight. If that time is less than 4-minutes and 45-seconds, the safelight does not meet minimum requirements. 6.1.2 Collective Safelight Check. a. Follow the above procedures with the following exceptions: turn on all the safelights in the exposure room when performing step e and expose the film to safelight at the location where film is normally opened. b. If the test results do not meet minimum criteria, follow the guidance below. (1) Replace safelight filters that are faded, cracked, scratched, not designated for industrial radiographic film, or do not fit properly. (2) Replace safelight bulbs exceeding the wattage recommended by the manufacturer. (3) Replace unserviceable safelights, such as those emitting ambient light. (4) Eliminate or reconfigure uncontrollable ambient light sources such as doorways, ventilating and heating ducts/vents, faulty film pass through box, building structural cracks, and holes around pipes and electrical wiring. (5) In the event the individual safelight tests are all within acceptable tolerance, but the collective safelight test is unacceptable, investigate the validity of the individual safelight tests. If the results of these tests are correct, reduce the number of safelights in the darkroom. 6.1.3 Developer Testing. a. Expose a piece of class 4 film and a step wedge to X-rays. (Class 4 film = Kodak AA, FUJI IX100, AFGA D7) Five sheets of X-ray film may be exposed at the same time when using a steel wedge and three sheets when an aluminum wedge is used. Expose the film sufficiently to present the whole range of densities from the step wedge. b. Cut the film into thin strips and seal securely to prevent exposure to light. c. Process the first strip with fresh developer. Save the strip to use as a reference. d. Once a week during the life of the developer, process another strip and compare the resulting density reading with the reference strip.
6-2
T.O. 33B-1-2 e. If a variation in excess of 0.3 density units occurs, the developer will need to be changed. f. Repeat the process each time the developer is changed. 6.1.4 Fixer Control. Fixer control is a measurement of the replenishment rate of an automatic processor. Follow the instructions in the owner’s manual for making this measurement. Generally, a graduated cylinder is used to capture the fixer being pumped into the tank while processing one piece of 14x17 film. The amount should measure between 170 and 190 ml. 6.1.5 Safelight Filter Check. Check safelight filters for fading, cracks, crazed, improper fit, scratched, or filters not designated for industrial radiographic film. Replace filters as required. 6.1.6 Interlock Operational Check. An inspection of the x-ray interlock system is required daily if the X-ray facility is used every day. For facilities not used every day a prior to use inspection is required. The interlock operational check SHALL be performed at least every six-months for seldom-used facilities. AFTO form 135 may be used to document the interlock operational check. The operational check will include as a minimum the following checklist items: • • • • • • • • •
Do all interlock door switches stop X-ray production if the door is opened? Are all rotating beacons operational? Does the audible alarm sound for 20 seconds prior to X-ray emission? Are all emergency stop buttons unobstructed and operational? Is the shielded radiation utilization log current? Does it include a facility survey, local operating procedures, emergency procedures, and ORMs within arms reach of the console? Does all personnel involved with X-ray operations have a TLD and a PAD, DAD, or equivalent approved direct reading dosimeter affixed to the trunk of the body and outside of their clothing? Does the shielded facility have legible and unobstructed warning signs inside and outside? Is at least one calibrated and operable survey meter ready for X-ray operations? Has the AFTO form 140 been documented for the battery and operational check?
6.1.7 Survey Meter Operational Check. The survey meter SHALL be checked by the user with a radiation check source prior to the first monitoring operation of the day, and at two-week intervals for instruments not in daily use.
6-3/(6-4 blank)
