PETRONAS TECHNICAL STANDARDS MAINTENANCE MANAGEMENT
PROCEDURAL SPECIFICATION
RADIOGRAPHIC INSPECTION
PTS 50.014 MAY 1991
PREFACE
PETRONAS Technical Standards (PTS) publications reflect the views, at the time of publication, of PETRONAS OPUs/Divisions. They are based on the experience acquired during the involvement with the design, construction, operation and maintenance of processing units and facilities. Where appropriate they are based on, or reference is made to, national and international standards and codes of practice. The objective is to set the recommended standard for good technical practice to be applied by PETRONAS' OPUs in oil and gas production facilities, refineries, gas processing plants, chemical plants, marketing facilities or any other such facility, and thereby to achieve maximum technical and economic benefit from standardisation. The information set forth in these publications is provided to users for their consideration and decision to implement. This is of particular importance where PTS may not cover every requirement or diversity of condition at each locality. The system of PTS is expected to be sufficiently flexible to allow individual operating units to adapt the information set forth in PTS to their own environment and requirements. When Contractors or Manufacturers/Suppliers use PTS they shall be solely responsible for the quality of work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, the Principal will expect them to follow those design and engineering practices which will achieve the same level of integrity as reflected in the PTS. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the Principal or its technical advisor. The right to use PTS rests with three categories of users : 1) 2) 3)
PETRONAS and its affiliates. Other parties who are authorised to use PTS subject to appropriate contractual arrangements. Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) and 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards.
Subject to any particular terms and conditions as may be set forth in specific agreements with users, PETRONAS disclaims any liability of whatsoever nature for any damage (including injury or death) suffered by any company or person whomsoever as a result of or in connection with the use, application or implementation of any PTS, combination of PTS or any part thereof. The benefit of this disclaimer shall inure in all respects to PETRONAS and/or any company affiliated to PETRONAS that may issue PTS or require the use of PTS. Without prejudice to any specific terms in respect of confidentiality under relevant contractual arrangements, PTS shall not, without the prior written consent of PETRONAS, be disclosed by users to any company or person whomsoever and the PTS shall be used exclusively for the purpose they have been provided to the user. They shall be returned after use, including any copies which shall only be made by users with the express prior written consent of PETRONAS. The copyright of PTS vests in PETRONAS. Users shall arrange for PTS to be held in safe custody and PETRONAS may at any time require information satisfactory to PETRONAS in order to ascertain how users implement this requirement.
CONTENTS 1. SCOPE 2. DEFINITIONS 3. ABBREVIATIONS 4. REFERENCES 5. SPECIFICATION REQUIREMENTS 5.1 Personnel Qualification 5.2 Radiation Safety 5.3 Procedure 5.4 Equipment 5.5 Radiographic Films 5.6 Location Markers 5.7 System of Identification 5.8 Image Quality Indicator (IQI) 5.9 Diagnostic Film Length (DFL) 5.10 Radiographic Techniques 5.11 Quality of Radiographs 5.12 Geometric Unsharpness 5.13 Back Scatter Radiation Check 5.14 Density 5.15 Sensitivity 5.16 Film Processing 5.17 Viewing Facilities 5.18 Acceptance Criteria 5.19 Records and Reports 5.20 Packing of Film 6. APPENDICES APPENDIX 1. APPENDIX 2. APPENDIX 3. APPENDIX 4.
REVISION REGISTER Revision No.
Date
Details of Revision
1
9/83
First Issue
2
1/84
Entirely NA
3
5/91
Revised Entirely
1. SCOPE This Standard Engineering Specification describes the requirements for radiographic inspection of materials and fusion welds in all equipment including the following •
pressure vessel
•
process piping
•
on and offshore pipelines
•
tanks
•
offshore structures
1.2 The acceptance/rejection criteria of radiographic inspection of each equipment shall be as stated in the applicable contract document.
2. DEFINITIONS Certification -
written testimony of qualification
Company -
shall mean PETRONAS and its Group of Companies and Subsidiaries/Associated companies.
Contractor -
the party which enters into a contract with the Company for the execution of work as detailed in a written agreement.
Employer -
corporate, private or public entity which employs personnel for wages, salary, fees or other considerations.
Qualification -
demonstrated skill, training knowledge and experience required for personnel to properly perform the duties of a specific job.
Shall and Should - the word 'shall' is to be understood as mandatory and the word 'should' as strongly recommended to comply with the requirements of this Specification. Training -
the programme developed to impart knowledge and skills necessary for qualification.
Written Practice
- the specific requirements which define the employer's procedure for the qualification and certification of non-destructive testing personnel.
3. ABBREVIATIONS AELB -
Atomic Energy Licensing Board, Malaysia.
ASTM -
American Society for Testing and Materials.
IQI -
Image Quality Indicator.
NDT -
Non-destructive Testing
PCN -
Personnel certification in non-destructive testing, the British National Scheme for personnel certification in NDT.
SES -
Standard Engineering Specification.
TLD -
Thermoluminescent dosimeter.
4. REFERENCES ANSI/ASME V -
Non-destructive examination.
BS2600 -
Radiographic Examination of Fusion Welded Butt Joints in Steel.
BS2910 -
Methods for Radiographic Examination of Fusion Welded Circumferential Butt Joints in Steel Pipes.
DIN 54109 Part 1 -
Non-destructive testing; image quality of radiographs; concepts, image quality indicators, determination of image quality value.
5. SPECIFICATION REQUIREMENTS 5.1 Personnel Qualification •
all Radiographers and Assistant Radiographers shall be licensed by the Atomic Energy Licensing Board, Malaysia. (For work within Malaysia only).
5.1.1 Radiographer •
shall possess a valid NDT Level II certification in industrial radiography in accordance with the Employer's Written Practice or other recognised independent qualifications as determined by the Company.
•
shall have at least 2 years experience in industrial radiography of tubular structures, pipelines and piping systems. This experience shall be shown by documented evidence.
5.1.2 Assistant Radiographer •
shall possess a valid NDT Level I certification in radiography.
•
shall have at least 1 year of relevant experience as an assistant radiographer which is shown by documented evidence.
5.1.3 Radiographic Interpreters The Contractor shall proved" trained, experienced and qualified radiographic interpreter certified by the employer to NDT Level II or to PCN Level II or equivalent. The radiographer may also be the radiographic interpreter if he holds this qualification. 5.1.4 Employer Based Certification The employer of the radiographers shall submit his Written Practice to the Company for review, approval and audit. At the Company's sole discretion, mock-up tests shall be carried out to prove the competency of the proposed radiographers and interpreters. 5.2 Radiation Safety For radiation safety, the following shall be adhered to:•
Atomic Energy Licensing Act 1984 and its subsequent regulations. (For work in Malaysia only. For work outside Malaysia, the respective country's statutory requirements shall apply).
The Contractor shall submit his radiation safety and emergency to the Company for approval prior to the commencement of work.
The Contractor shall hold valid licences from the Atomic Energy Licensing Board for the activities involving radioactive sources and irradiating equipment. (For work in Malaysia only. For work outside Malaysia, the respective country's statutory requirement shall apply). The Contractor shall provide each radiographer with a film badge or TLD and a pocket dosimeter and each team, comprising of a radiographer and an assistant radiographer, a survey meter and a radiation alarm warning device. The survey meter and pocket dosimeter shall be calibrated annually or earlier by a laboratory recognised by AELB.
5.3 Procedure 5.3.1
The Contractor shall submit to the Company a written procedure specific to the job for prior approval, after which the radiographic techniques (contained in the procedure) for the various thickness and diameter ranges shall be qualified by producing satisfactory standard test radiographs.
5.3.2
The procedure shall include, as a minimum, the relevant elements contained in this Standards Engineering Specification, relevant to the job.
5.4 Equipment 5.4.1
The Contractor shall provide the radiographs with all the necessary equipment, tools and consumable to perform the radiographic inspection such as:-
Approved remote wind-out gamma radiography systems. Collimators and lead sheets Emergency handling tools e.g. lead shot bags, tongs, lead pot and assorted tools. Isotope transport container X-ray machines X-ray crawlers Cassettes complete with lead screens or fluorometallic intensifying screen Sets of lead numbers and letters Radiation warning signs, rope barriers, buntings, flashing warning lights, hand crank claxon, etc. Films (ASTM film type 1 and 2) Darkroom complete with accessories and processing facilities. DIN 54109 or equivalent wire penetrameters. The Company reserves the right to inspect these items of equipment for their suitability for their intended purpose and to ensure their safe working condition.
5.4.2 Gamma Radiography System and Radiation Energy 5.4.2.1 Gamma Radiography System The gamma radiography system shall be approved by AELB. (For work in Malaysia only). The system shall be of the remote wind-out type e.g. Tech-Ops. The radioisotope shall be as small as obtainable. The source activity for Iridium 192 shall be between 12 and 25 curies, For other sources, the activity shall be agreed upon between the Company and the Contractor. 5.4.2.2 Gamma Radiation The recommended minimum thickness for which radioactive isotopes shall be used is as follows:Minimum Thickness (in.) Material
Iridium 192
Cobalt 60
Steel
0.375
1.50
Copper/High Nickel
0.65
1.30
Aluminium
2.50
-
The minimum recommended thickness may be reduced when the radiographic techniques demonstrate that the required radiographic sensitivity has been obtained. 5.4.3 X-ray Machine, Crawler And Radiation Energy 5.4.3.1 X-ray Machine The X-ray machine shall be of a make approved by AELB, (for work in Malaysia only) having a maximum voltage of about 400 KV. The focal spot of this machine shall be determined by the pin hole method. There shall be a spare set of equipment at an inspection location to provide continuity of radiographic inspection in the event that one set malfunctions. 5.4.3.2 X-ray Crawler X-ray crawler shall be used in conjunction with an automatic film processor for weld inspection of submarine pipelines on a laybarge. The crawler shall be of a make approved by AELB (for work in Malaysia only) and suitable for the diameter of the pipe being laid. A back-up set shall be available on board for continuity of work in the event that one set malfunctions. 5.4.3.3 Radiation Energy The maximum voltage used in radiographic inspection shall not exceed the values shown in Appendix 1 for the respective materials.
5.5 Radiographic Films 5.5.1 Type Unless otherwise agreed by the Company, only double coated industrial films having low-speed, very fine grain, very high contrast (ASTM film type 1) or medium speed, fine grain, high contrast (ASTM film type 2) suitable for use with lead screens or fluorometallic intensifying screens shall be used.
5.5.2 Storage All unexposed films shall be stored in a clean dry store where they will not be subjected to: •
Chemical vapours, fumes
•
Radiation and light
•
Excessive heat and humidity
•
Undue pressure
5.5.3 Fog Density Every box or roll of film shall be checked for fog density. If it is greater than 0.30 H & D, as measured with a densitometer calibrated against a National Bureau of Standards, the whole box or roll shall be rejected. 5.5.4 Cu-Ni and Stainless Steels For radiography of Cu-Ni and stainless steel welds, only type 1 films shall be used.
5.6 Location Markers 5.6.1
Location lead markers which are to appear as radiographic images on film shall be placed on the component and their locations shall be marked on the surface of the component being radiographed to provide traceability.
5.6.2
Location markers for the various techniques shall be in accordance with Appendix 2.
5.7 System of Identification A system shall be used to produce permanent identification on the radiograph with at least the following information: •
Contract
•
Component
•
Weld or part number
•
Contractor name
•
Date of radiography
•
Welder identification
•
Repairs (R1, R2....)
This information shall not obscure the area of interest.
5.8 Image Quality Indicator (IQI) 5.8.1 Make IQIs shall be manufactured of radiographically similar material to the object being radiographed.
5.8.2 Type The DIN 54 109 (1962) or ISO wire type IQI shall be used to provide a guide to the quality of the radiographs produced. Other types of IQI may be used upon prior approval from the Company. 5.8.3 Placement of IQI A wire type IQI shall be placed on the source side with the smallest wire outward and just within the end of the area of interest (diagnostic film length). In addition, for weld inspection, the wires shall be placed across and perpendicular to the weld axis. Where placement of IQI on the source side is impracticable, it may be placed on the film side provided the following condition is met:Set up a test piece of the same dimensions as the production weld to be radiographed on which IQIs can be placed on both source and film sides. Place a lead letter 'F' next to the film side IQI. Take a test radiograph using the same radiographic technique that will be used on the production weld. Use the source side IQI to achieve the contractual sensitivity and, for correlation with the radiographic sensitivity for production welds, record the corresponding sensitivity on the film side IQI. 5.8.4 Film Side IQI All film side IQIs shall be identified by the letter 'F'. 5.8.5 Number of IQI (a) Panoramic Exposure When a circumferential weld can be radiographed in a single exposure, using a single source inside, at least three IQIs equally spaced around the circumference shall be used. (b) Elliptical Exposure When a weld is radiographed using a double wall double image technique, one IQI on the source side shall be used. (c) Multiple Exposure When the length of a film to be interpreted (diagnostic film length) is eight inches and longer, two IQIs placed at each end of the diagnostic film length shall be used. When the diagnostic film length is less than eight inches, one IQI placed at one end of the diagnostic film length shall be used.
5.9 Diagnostic Film Length (DFL) In order to meet the density requirements and to allow for the fall-off in flaw sensitivity towards the ends of the radiograph due to an increase in penetrated thickness and to geometric effects, the diagnostic film length (DFL) shall be limited to thickness not more than 110% of the penetrated thickness at the centre of the radiograph.
5.10 Radiographic Techniques 5.10.1
In the procedure submitted to the Company, the Contractor shall formulate and incorporate detailed radiographic techniques, including sketches, that are to be used in the inspection. Standard test radiographs shall be produced based on the parameters of the approved techniques.
Appendix 3 shows a sample of the Company's radiographic technique sheet. The Contractor's technique sheet shall contain, as a minimum the details appearing therein. 5.10.2 Single Wall Technique In this technique, the radiation passes through only one wall of the object. An adequate number of exposures (multiple) shall be made to ensure that the required coverage has been obtained. 5.10.3 Double Wall Technique When it is not practical to use a single 'Wall technique, the following shall be used:(a) Single-wall Viewing In this technique, the radiation passes through two walls, but only the material or weld near the film side is viewed. An adequate number of exposures shall be made to ensure that the required coverage has been obtained. For complete coverage of a circumferential weld or materials, a minimum of three exposures at 120 degrees to each other shall be made. (b) Double-wall Viewing This technique applies to materials or welds having 31/2 inches or less in outside diameter. In this technique, the radiation passes through two walls and the material or weld in both walls is viewed on the same radiograph. For this technique, only a source side IQI shall be used. For welds, the radiation beam may be offset from the plane of the weld at an angle sufficient to separate the images of the source side and film side portions of the weld so that there is no overlap of areas to be interpreted. For complete coverage, a minimum of two exposures at 90 degrees to each other shall be made for each joint. As an alternative, the weld may be radiographed with the radiation beam positioned so that the images of both walls are superimposed. For complete coverage a minimum of three exposures at either 60 or 120 degrees to each other shall be made for each joint. This technique shall be used for thick walled pipe welds of diameters equal to or less than 1 inch. 5.11 Quality of Radiographs All radiographs shall be free from mechanical, chemical or other blemishes to the extent that they shall not mask or be confused with the image of any flaw in the area of interest of the radiograph. Such blemishes, include, but are not limited to: •
fog
•
processing defects such as streaks, water marks or chemical stains
•
scratches, finger marks, crimps, dirtiness, static marks, smudges or tears
•
false indications due to defective screens or internal faults
•
interference on areas of interest by lead markers
5.12 Geometric Unsharpness 5.12.1 Formula Geometric unsharpness of a radiograph shall be determined in accordance with UG = Fd/D
Where UG = geometric unsharpness F = source size, the maximum projected dimension of the radiating source or focal spot in the plane perpendicular to the distance D from the weld or object being radiographed in inches. D = source to weld or object distance in inches d = source side of weld or object to the film distance in inches. 5.12.2 Limitations The geometric unsharpness UG of the radiograph shall not exceed:Other than Standards
British Standards
British
Weld or object
UG
Radiation
UG(mm)
thickness (in)
(in)
100 KV
0.05
Under 2
0.020
200 KV
0.09
2 through 3
0.030
300 KV
0.12
Over 3 through 4
0.040
400 KV
0.15
Greater than 4
0.070
Iridium 192
0.17
Cobalt 60
0.35
5.13 Back Scatter Radiation Check As a check on back scattered radiation, a lead symbol "B" with minimum dimensions of ½ in. high x 1/16 in. thick shall be attached to the back of the film holder. If a light image of "B" appears on the darker background of the radiograph, the protection from back scatter is insufficient and the radiograph shall be rejected. However, a dark image of "B" on a lighter background is not cause for rejection.
5.14 Density The density on the area of interest shall be 2.0 minimum for both radiographs made with an X-ray source and a gamma source. The maximum density shall be 3.0. The density measured shall be H & D density. In a radiograph, the densities within the diagnostic film length of the area of interest shall not vary by more than 30% between the lighter and darker areas. Density shall be measured using a densitometer calibrated to a National Standard by an accredited laboratory or by visual comparison with a calibrated film-strip.
5.15 Sensitivity 5.15.1 Sensitivity is usually taken an a measure of image quality and is expressed as a percentage in the following equation:-
Sensitivity =
diameter of the smallest visible wire on the radiograph x 100 -----------------------------------------------specimen thickness
Unless agreed otherwise by the Company, the sensitivity, using wire type IQI, shall be less than or equal to 2%. In sensitivity computation, the source side IQI shall be used. 5.15.2 The thickness used for sensitivity computation shall be as follows:(a)
Single-wall Technique and Single-wall Viewing The thickness of the specimen.
(b)
Double-wall Technique and Single-wall Viewing The nominal single wall thickness adjacent to the film of the specimen.
(c)
Double-wall Technique and Double-wall Viewing The nominal double-wall thickness of the specimen.
5.15.3 For weldment radiography, the thickness used for sensitivity computation shall include the thickness of the weld reinforcement a permitted in the applicable code/standard/ specification. 5.16 Film Processing 5.16.1 In his Procedure submitted to the Company for approval, the Contractor shall. include detailed film processing procedures and equipment and accessories used to product quality radiographs. He shall consult the film and processing chemicals manufacturers for detailed recommendations for film processing. 5.16.2 Manual Procedure Developing time varies with temperature. It is therefore imperative that the film manufacturer's recommended developing time and temperature shall be adhered to. The fixing time shall be twice the time needed to clear an unexposed film. An acid stop bath shall be used between the developer and fixer. Developed films shall be washed thoroughly for a minimum for ten minutes in running water and twenty minutes in still water. 5.16.3 Drying Films shall be dried in a dryer which is in good, safe condition e.g. Agfa-Gevaert structurix or a drying cabinet, at temperature not exceeding 55ºC. When there is no urgency, films may be dried in a dry, dust free room.. No films shall be subjected to continued exposure to a temperature higher than 40ºC (104ºF). 5.16.4 Automatic Processing on a Laybarge The automatic processor shall be of Agfa-Gevaert or equivalent and able to handle the work load and speed required by a laybarge. The processor shall maintain the chemical solutions at the proper temperature, agitate and replenish the solutions automatically and transport the films mechanically at a carefully controlled speed throughout the processing cycle. It is imperative that the processor, films and chemicals are compatibly matched. 5.16.5 Film Storage Life Films shall be processed to ensure their integrity for at least five years under normal storage conditions.
5.17 Viewing Facilities 5.17.1 Viewing room shall provide subdued background lighting of an intensity that will not cause troublesome reflections, shadows or glare on the radiographs. Viewers shall provide variable light intensities to view radiographs up to 3.50 H & D density. 5.17.2
All radiographs shall be viewed, interpreted and evaluated in the properly dried condition.
5.18 Acceptance Criteria The acceptance and rejection criteria shall be in accordance with the specific contract specification, codes and standards. The Company shall have the final decision on the interpretation and evaluation of radiographs.
5.19 Records and Reports The Contractor shall submit records and reports in accordance with the following:(a)
Films and objects (e.g. welds) radiographed shall be clearly identified in a manner approved by the Company so that the radiograph and the weld to which it pertains to can be immediately located.
(b)
A summary of all objects radiographed and the results of the inspection i.e. cut-out, grind and repair, etc., in accordance with the Company's requirements, shall be furnished to the Company daily.
(c)
The records of all objects radiographed including those of rejected welds, repairs and any reshoots shall be properly catalogued and filled to permit ready retrieval and identification during and after construction.
(e)
Completed radiographed reports shall accompany all interpreted radiographs.
Appendix 4 shows a sample of the Company's radiographic report for welds. The Contractor's report shall contain as a minimum the details appearing therein.
5.20 Packing of Film All sheet films shall be inserted in the paper sleeves and packed into their original boxes after evaluation. All roll films (Rollpac) shall be rolled up properly and packed into suitable boxes after evaluation. On completion of the projected these boxes shall be packed into cartons suitable for archiving as instructed by the Company. Suitable markings shall be provided on the boxes and cartons for easy retrieval including proper documentation as requires by the Company.
APPENDICES Appendix 1
Maximum Voltage
Appendix 2
Location Marker Sketches
Appendix 3
Radiographic Technique
Appendix 4
Radiographic Report
6. APPENDICES Appendix 1. Maximum Voltage for Steel
Maximum Voltage for Alloys of Copper and/or High Nickel
Maximum Voltage for Aluminium and Aluminium Alloys
Appendix 2. Location Marker Sketches
Appendix 3. Radiographic Technique
Appendix 4. Radiographic Report Sarawak Shell Berhad Sabah Shell Petroleum Company Limited
