Eddy Current (RFT) Procedure

Copy No.: 4.0

Technical Procedure Non Destructive Testing & Inspection Laboratory - Motabaqah Remote Field Eddy Current Testing

NDT.TP.701.ET.03.Ry

RFT Eddy Current Testing Procedure NDT.TP.701.ET.03.Ry

Effective Date eviewed By Prepared By R eviewed Title

ASNT Level III

Technical Manager

Name

Muhammad Kashif

Amir Sajjad

A pproved By Lab Manager/ Quality Manager

Sign

Issue No. 1.0

Issue Date November.2015

Revision No. A.00

17.November.2015 Copy No. Distribution Deputy of GMO 1 Lab Manager 2 3 4

Quality Manager Technical Manager

5

SAC

Issue By Quality Manager

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NDT.TP.701.ET.03.Ry

Table of Contents No.

Item

Page

1.

Table of Contents

2

2.

Amendment Page

3

3.

Purpose

4

4.

Scope

4

5.

Responsibilities

4

6.

References

4

7.

Pre-Requisites

5

8.

Definitions/Abbreviations

5

9.

Limitations

6

10.

Equipment & Accessories

7

11.

System Calibration

9

12.

Examination & Recording

10

13.

Acceptance Criteria

11

14.

Report & Record

11

15.

Recording Criteria

11

16.

Analysis Criteria

11

16.

Revision Page

12

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Amendment Page 1

2

3

4

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6

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9

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1.


NDT.TP.701.ET.03.Ry

Purpose: The purpose of this procedure is provide guidelines to NDT personnel of Motabaqah to carrying out Remote Field Testing (RFT) for the detection and locate of tube wall thinning and localized wall loss in the straight ferromagnetic tubes.

2.

Scope: This Procedure is applicable for RFT to detect tube wall thinning and localized wall loss ferromagnetic tubes of diameter ranging from 12.70 – 50.80 mm and thickness in 0.71 to 3.40 mm. This procedure is specifically applicable to RFT examination using an internal coil assembly for straight tubes excluding U-bend. This practice does not establish tube acceptance criteria, the tube acceptance criteria must be specified by the using parties/plant/client.

3.

4.

5.

Responsibilities: 3.1

ASNT NDT Level III Electromagnetic Testing is responsible to prepare the procedure and Technical Manager or his designee is responsible for review, explanation and modification of this procedure

3.2

Quality Manager NDT and Deputy General Manager Operation are responsible to review & approve the procedure. Quality Manager NDT will also help/assist for its effective implementation.

3.3

ET level – 1 qualified person shall perform inspection according to approved procedure except analysis of results under supervision of ET Level II or III

3.4

ET level – II or higher qualified person can perform inspection including interpretation, analysis and evaluation of the results.

References: 4.1.

SNT-TC-1A

Recommended practice for Personnel qualification & certification in Non Destructive Testing

4.2.

ASME Section V, Article 17

Electromagnetic Testing , Remote Field Testing of ferromagnetic tubes

4.3.

ASTM E-2096

Standard Practice for In Situ Examination of Ferromagnetic Heat Exchangers Tubes using Remote Field Testing.

4.4.

ASTM E 543

Practice for Agencies Performing Nondestructive Testing

4.5.

ASTM E1316

Terminology for Nondestructive Examinations

Pre – Requisites: 5.1 Prior to remote field testing a reference standard shall be manufactured for the specific test of the same nominal size and material (chemical composition & product form) as that to be examined. The intent of this reference standard is to establish and verify system response. Reference standard for tubes in remote field testing shall be manufactured as per ASTM E 2096. Issue No. 1.0


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5.2


NDT.TP.701.ET.03.Ry

The tubes should be cleaned and dried by client before the start of inspection. The tubes should be free from water, scale and mud.

6.

5.3.

The inspection should be carried out after proper cleaning

5.4

Scaffolding and other arrangement needed to gain access to the required points of inspection will be arranged by client.

5.5

Power supply, air supply, lighting arrangement 24V and electrical earthing /ground should be provided by the client.

5.6

Client should brief the inspector involved in the implementation of this procedure regarding the operation/accident history which later on will enable analyst for accessing the tube damage/condition.

Definitions / Abbreviations : 6.1. QC: Quality Control 6.2.

ET:

Electromagnetic Testing

6.3.

RFT:

Remote Field Testing, a nondestructive test method that measures changes in the remote field to detect and characterize discontinuities.

6.4.

NDTIL:

Non-Destructive Testing & Inspection Lab

6.5.

ASTM:

American Society for Testing and Material

6.6.

NDT:

Non-Destructive Testing

6.7.

ASME:

American Society of Mechanical Engineers

6.8.

Frequency:

The number of cycles per second of alternating electric current induced in the tubular product

6.9.

Nominal Point:

A point on the phase-amplitude diagram representing data from nominal tube.

6.10

Phase-Amplitude: A two-dimensional representation of detector output voltage, with angle representing phase with respect to a reference signal, and radius representing amplitude. 6.11. Indications: Eddy current signals caused by any change in the uniformity of a tube. These changes in uniformity affect the electric characteristic of the tube 6.12. Sensitivity Control: The control in the instrument which adjusts the amplifier gain and is one of the factors that determines the capacity to detect discontinuities 6.13. Reference A piece of same material, dimensions and heat treatment condition Standard: with artificial discontinuities used for establishing the test sensitivity setting, periodically checking and adjusting sensitivity setting as required. Issue No. 1.0


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6.14. Non-Quantifiable Indication: 6.15. End Effect:

NDT.TP.701.ET.03.Ry

A non-quantifiable indication is a reportable indication that cannot be characterized. The indication shall be considered a flaw until resolved future inspections or otherwise The losses in sensitivity to discontinuities located near the extreme ends of the tube as test coil enter or leave the ends of the tube.

7. Limitations: 7.1.

Applicable to ferromagnetic tubes only.

7.2.

Sensitive to surface variations therefore, requires smooth & clean surface

7.3.

Indication near tube sheet or edge may not be classified due to end effect.

7.4

Combination of defects on circumference has to be approximated due to net change in magnetic field of the test circuit

7.5

Any indication which remains unresolved shall be reported as non-quantifiable indication until resolved in future inspections or otherwise.

7.6

A reference standard is required for system calibration else the examination cannot be performed.

8. Equipments & Accessories : 8.1.

Instrumentation: 8.1.1 The electronic instrumentation shall be capable of creating exciter signals of one or more frequencies appropriate to the tube material 8.1.2 The apparatus shall be capable of phase and amplitude analysis of detector outputs at each frequency, independent of other frequencies in use simultaneously. 8.1.3 The instrument shall display data in real time and recording data and system settings in a manner that allows archiving and later recall of all data and system settings for each tube 8.1.4 The data acquisition and analysis will be carried out by the following equipment: Apollo Multi-Channel / Multi-Frequency RFT System

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Probe Inputs

:8

Channels

: 8 simultaneously

Number of frequencies

:4

Gain Range

: 0 to 40GB

Frequency Range

: 1 Hz to 10MHz

Probe Balancing

: Electronic probe balancing (hardware null)

Manufacturer

: GE Measurement & Control, USA


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8.2.


NDT.TP.701.ET.03.Ry

RFT Probe: The probes should be of an appropriate configuration and size for the tube being examined and compatible with the testing equipment.

8.3

RFT Tube Reference Standard: 8.3.1

RFT tube standards should be of the same nominal dimensions, material type and grade as the tubes to be examined.

8.3.2

Typical artificial flaws and flaw characterization standards are as under :

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8.3.3

NDT.TP.701.ET.03.Ry

The RFT system reference standard has specific artificial flaws. It is used to set up and standardize a remote field system and to indicate flaw detection sensitivity. The artificial flaws for the RFT system reference standard are as follows:

Through-Hole: A through-hole (Fig. 1, Flaw A) whose diameter is e qual to the tube wall thickness multiplied by a specified factor. For tubes of outside diameter less than 1.000 in. (25.40 mm), the factor is 1. For tubes of outside diameter greater than or equal to 1.000 in., the factor is 1.5. Flat-Milled Flaw: A flat-milled flaw (Fig. 1, Flaw B) of a depth of 50% and axial length one half of the tube nominal outside diameter. The flat should be side milled using a milling tool of a diameter of 0.250 in. (6.35 mm) to create rounded corners. Short Circumferential Groove: A short circumferential groove (Fig. 1, Flaw C) of a depth of 20% and axial length of 0.625 in. (15.88 mm). Edges shall be angled at 105 degree. Wear Scar: A simulated wear scar from a tube support plate (Fig. 1, Flaw D) consisting of a circumferentially tapered groove, 40% deep, extending over 180 deg of the tube circumference. Axial length measured at the bottom surface of the flaw shall be 0.625 in. (1 5.88 mm). Edges shall be angled at 105 degree . Tapered Flaw: tapered flaw simulating near-tube-support erosion (Fig. 1, Flaw E) consisting of a groove 60% deep tapered circumferentially and in both directions axially, the steep side of the flaw shall be angled at 65 deg to the tube axis. The shallow side of the flaw shall be axially tapered so that it extends an axial distance of four tube diameters from the deepest point. The circumferential extent at the maximum point shall be 90 deg. Long Circumferential Groove: A long circumferential groove (Fig. 1, Flaw F) of a depth of 20% and recommended axial length of two tube diameters, Length is optional according to application, Edges shall be angled at 105 degree Note: See figure 1, on next page

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FIGURE-1: M anufacturing Refer enc e fo r R F T S y s t e m R e f e r e n c e Standard

9.

System Calibration : System calibration shall be performed as below and according Figure-2, given on Ne xt page 9.1.

Differential Channels: The phase rotation of the base frequency (F1) shall be adjusted so that the signal from the through-wall hole (TH) appears approximately along the Y (vertical) axis and that the signal from the tube support plate (TSP) lies in the upper left-hand and lowe r right-hand quadrants. When properly adjusted, the differential signals should be displayed on a voltage plane display

9.2.

Absolute Channels: The absolute channels should be calibrated by setting up the tube support/baffle plate signal at zero degrees (horizontal at X-axis), While keeping the grove vertical upwards.

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Figure-2: The following settings are required for differential and absolute channels calibration

10. Examination and Recording: 10.1. Scanning Direction: Data shall be recorded as the probe traverses the tube. The data may be gathered in a “Timed” mode. 10.2. Scanning Speed: The probe speed shall be dependent on the base frequency and sample rate and shall be no faster than the speed required obtaining a clear signal from the reference tube standard. 10.3. Tube Sheet Marking: The tube number shall be marked on the tube sheet as Rows and Columns or if available additional info of zones and flow passes. Issue No. 1.0


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10.4.


NDT.TP.701.ET.03.Ry

Pull/Push Method: Manual push/pull by hands shall be utilized for inspection.

10.5. Recording of Signals: The recording of remote field signals shall be done while pulling the probe through the tube. The tube number will be noted. The signals on storage device (hard disk) should be saved. 11.

Acceptance Criteria: This procedure does not establish tube acceptance criteria; the tube acceptance criteria must be specified by the using parties/manufacturer/plant/client.

12.

Report and Record: At the end of the inspection and data analysis a report will be filled by inspectors and analyst on the specific duly signed by Technical Manager. Report shall be kept as record in file.

13.

Recording Criteria: Location of indication will be reported along the length of the tube with respect to support plates and depth range of the indications through the tube wall and wall thinning should be reported.

14.

Analysis Criteria: The maximum evaluation depth of flaws and tube wall thinning shall be analyzed in terms of percentage. When the loss of tube wall is less than 20% the exact percentage of tube wall loss need not to be recorded and reported

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Eddy Current (RFT) Procedure

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