METHOD STATEMENT FOR GAMMA RAY INSPECTION PROCEDURE.doc

CENA TECH

CLIENT: OILSERV LIMITED

DOCUMENT NUMBER: NDT/GRI/QAC - 040/CENA TECHREVISIO

NDESCRIPTION OF MODIFICATION

PREPARED BY

REVIEWED BY APPROVEDBY CLIENT REP.

DATE OF ISSUE

0 FIRST ISSUE CHRIS CYRIL OBUSE 05/06/20141 AUDIT SCHEDULE23

Distribution - Uncontrolled Copy

GAMMA RAY INSPECTION PROCEDURE

OF WELDED JOINTS

1


CENA TECH

GAMMA RAY INSPECTION OF WELDED JOINTS

TABLE OF CONTENTS

1. PURPOSE2. SCOPE3. REFERENCES4. PERSONNEL QUALIFICATION5. SURFACE PREPARATION6. EQUIPMENT MATERIAL AND CONSUMABLES7. SAFETY8. CALIBRATION9. QUALITY OF RADIOGRAPH10. RADIOGRAPHIC DENSITY11. GEOMETRIC UNSHARPNESS 12. IDENTIFICATION / LOCATION MARKERS ON RADIOGRAPHS13. IMAGE QUALITY INDICATOR (IQI)14. RADIOGRAPH TECHNIQUE15. EXPOSURE TIME CALCULATOR16. PROCESSING OF RADIOGRAPH17. VIEWING CONDITION18. ACCEPTANCE CRITERIA19. PRESENTATION OF COMPLETED RADIOGRAPHS20. STORAGE OF PROCESSED RADIOGRAPHS21. REPORT22. DOCUMENTATION


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1. PURPOSE:The purpose of the procedure is intended to provide OILSERV and involved authorities with the information concerning methods, techniques, equipment and personnel to be employed in carrying out Radiographic Inspection by CENA TECH.

2. SCOPE:This procedure establishes the requirement of radiographic examination of carbon and stainless steel Weld in Piping and Structures whose wall thickness range from 3mm to 75mm.

3. REFERENCES:The latest revisions of the following standards and specifications shall be used.

3.1. SNT-TC-1A: Recommended practice for the qualification and certification of Non- destructive testing personnel, Supplement A.

3.2. NDT/PQC/QAC-020/CT: CENA TECH written practice for the qualification and certification of CENA TECH Personnel.

3.3. ASME SEC V: Boiler and Pressure vessel code - Non- destructive Examination.

3.4. ASME E 94: Standard testing for radiographic testing3.5. MPN LPPG 03-11-06: Radiographic Work and Radiographic

Isotopes, Storage, Use and Control.

4. PERSONNEL QUALIFICATION:All personnel shall be qualified for level II (gamma radiography without interpretation). Only Level III/Inspection engineer


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(RADIOGRAPHIC TESING PERSONNEL) shall interpret radiographs. Qualification as per CENA TECH written practice, or equivalent as approved by the Client

5. SURFACE PREPARATION.5.1. The furnished surface of all butt- Welded joints may be

with base metal or may have uniform crown.5.2. Excessive weld ripples or welds irregularity on both the

inside (where accessible) and outside shall be removed by suitable process to avoid any confusion in the resulting radiograph.

6. EQUIPMENT MATERIAL AND CONSUMABLES.

6.1 CONTAINERAMERSHAM and/or NECSA made IR-192 Gamma ray source container TECH/OPS 660 remote type with maximum Curie of 80Ci or similar.

6.2 RADIOGRAPHIC FILMRadiographic film shall be as described in ASME Section V: Article 22: SE–94, depending on application or as specified in the contract or as per Client specification. If required by project specifications or contract it shall be of roll-pack type.

6.2.1. Type I shall be KODAK MX OR AGFA D4. Or similar6.2.2. Type II shall be KODAK AX OR AGFA D7. Or similar

6.3. INTENSIFYING SCREENS AND CASSETTES:


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6.3.1. Only lead intensifying screen of 0.125mm in front and 0.125 / 0.125mm in the back shall be used.

6.3.2. The cassettes shall be of Velcro type or double envelope type.

7. SAFETY. All radiographic examination shall be carried out in accordance with CENA TECH Radiation Safety Manual, Radiographic Protection Program, and Radiation Control

Procedure and Local Rules for Site Radiography, and Oilserv Safety requirements and National regulations

8. CALIBRATION: All equipment that requires calibration shall have valid current calibration certification.

9. QUALITY OF THE RADIOGRAPHS.All radiographs shall be free from mechanical, chemical or other blemishes to the extent that they do not mask or confuse the image of the discontinuity in the area of interest of the object being radiographed. Such blemishes include but not limited to the following:

Fogging, Process defects such as streaks, watermarks or chemical

strains,


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Scratches, finger marks, smudges or false indication due to defective screens.

10. RADIOGRAPHIC DENSITYThe film density through the area of the radiographic image shall be 2 for single viewing and 2.6 for composite viewing of double film, exposure with a maximum of 4 in either case. Either a calibrated densitometer or step wedge film comparison strip shall be used to measure the density of the radiograph.

11. GEOMETRIC UNSHARPNESSThe radiography technique used shall be such that the Geometric un-sharpness shall not exceed the following,

Material Thickness, inches

Geometric un- sharpness (Ugh) Maximum, in

< 2 0.020 2 to 3 0.030

Geometric un-sharpness is given by the formulaUg = F *t/ d

WhereUg = geometric un-sharpness.F = Size of Radiation source.t = Specimen thickness, when in contact with the film.d = Source to object distance

12. IDENTIFICATION AND LOCATION MARKERS ON RADIOGRAPH GENERAL


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A system of radiographic identification shall be used to produce a permanent and traceable record or part number. The letter R shall be placed to designate a radiograph of a repair area and may include – 1, -2, etc., for the number of repairs. Flash system of identification may be used with client’s approval according to relevant procedure.

LOCATION MARKERLocation lead marker shall be in form of metric number tapes and shall be maintained on the part during radiography and the datum shall be marked on the part by crayons to assist in marking of any defective area of the component or the weldments.

13. IMAGE QUALITY INDICATORSQuality radiograph with the appropriate IQI is the only indication of the proper radiographic inspection. Defective radiographs neither shall nor be accepted.

13.1 TYPE:13.1.1. The image quality indicators shall be of wire type and

comply with BSEN 462-1:1994 unless otherwise specified. The penetrameter dimension shall be appropriate to the size of the welds and penetrameter shall radiographically be the same material as the material being tested.

13.1.2. The IQI shall be selected on the basis of thickness of the weldment being tested, as set out below: 10 Wire Nos.10-16 for thickness range 5-20mm (0.2-0.75”)6 Wire Nos. 6-12 for thickness range 12.5-50mm (0.5-2.0”)1 Wire Nos. 1-7 for thickness range 40-160mm (1.6-6.3”)


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13 Wire Nos. 13-19 for thickness range 2.5-10mm (0.1-0.4”)

Penetrameter wire diameter in mm1 Wire Nos. 1—7 3.2 2.5 2.0 1.6 1.25 1.00 0.8

6 Wire Nos. 6—121.00 0.8 0.63 0.5 0.4 0.32 0.25

10 Wire Nos. 10—16 0.4 0.32 0.25 0.2 0.16 0.1250.1

13.1.3. For double wall exposure and double wall viewing the diameter of the wires employed shall be based on the nominal double wall thickness.

13.1.4 For double wall exposure and single wall viewing the diameter of the wire shall be based on the single wall thickness of the specimen

13.2 SENSITIVITY:13.2.1.The radiography shall be performed with technique of sufficient sensitivity to clearly display the penetrameter wire, the sensitivity shall be at least 2%, unless or otherwise mentioned.

13.2.2 Sensitivity shall be calculated by formula:

13.2.3 % Sensitivity = Diameter of the thinnest wire visible / thickness of the test piece including the reinforcement.

13.3 PLACEMENT OF THE PENETRAMETER.


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13.3.3. The penetrameter shall be on top of the weld, so that the wires are 90° to the weld. Whenever possible the penetrameter shall be placed on the source side unless if it is impractical demonstrated for the required sensitivity, the pentrameter may be placed on the film side and a lead letter F shall be placed on the penetrameter.

13.4.NUMBER OF PENETRAMETER13.4.1At least one penetrammeter shall be on each radiograph, when one or more films are used for an exposure. When the density is each expected to vary at the area of interest between –15% and +30% then an additional penetrameter shall be placed at the film at the area of interest.

13.4.2 When one or more films are used in a single exposure with the source at the center of the axis of the component, then 3 penetrameters spaced 120 degrees apart shall be used.

13.4.3 When four or more films are used for a single exposure of a section of the circumference then three penetrameters shall be placed, one in the mid of the section and the other two at each end.

13.4 DIAGNOSTIC FILM LENGTHThe length of the component under examination at each exposure shall be that the thickness of material penetrated at the extremities of the readable area, measured in the direction of the incident beam at that point, must generally not be exceeded by more than 10% of the actual thickness


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where the beam is aligned normal to the part, with the exception of DWSI which depend on number of exposures.

14. RADIOGRAPHIC TECHNIQ1UE.14.1 FILM INSIDE - SOURCE OUTSIDE (single wall/ single image :)

The source will be positioned so that the radiation beam is directed to the center of the section under examination and normal to the weld surface with a minimum of 1” overlaps for multiple exposures.

14.2 FILM OUTSIDE – SOURCE INSIDE (single wall/single image, panoramic)

The sources will be positioned so that it coincides. with the centre of the pipe and with the radiation beam normal to the pipe surface. The minimum overlap of film is 1’’ for loaded cassettes and 2” for roll pack film. The minimum diameter for this technique shall be 10”.

14.3. FILM OUTSIDE – SOURCE OUTSIDE ( Double wall/single image)The source will be positioned so that the radiation beam passes through the centre of the section under examination and will be offset from the plane through the weld by the minimum distance necessary to prevent the image of one side of the weld confusing the image of the other side. The film shall be placed diametrically opposite the source with minimum number of the three exposures at 120-deg displacement with an overlap of a


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minimum of 1”. Refer table 1 for diameter and thickness limitation.

14.4. Double wall/double image (elliptical)The source will be positioned so that the radiation beam passes through the centre of the pipe in the plane of the weld with the minimum (refer table 1) offset required to separate the top and the bottom image. Two exposures are at 90-deg displacement. The maximum diameter for this technique is 3½”.

14.5. Double wall/double image (super imposed)The source is positioned in such a way that the image of both walls is superimposed, a minimum of three exposures taken at either 60 deg or 120 deg to each other. This technique shall be applied for branch connections, weld lets and other weldments, when elliptical technique is unsatisfactory.


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Table 1

Number of exposures related to diameter and thickness of pipe

PIPE SIZE WALL THICKNESS NUMBER OF EXPOSURES1½” and smaller

All 2 elliptical exposures 90° apart at minimum of 15” sfd

2” to 2½” All 2 elliptical exposures 90° apart at minimum of 16” sfd

3 and 3½” Schedule 80 & below

3 contact shots

Above 80 to 160 4 contact shotsXX strong 6 contact shots

4” Schedule 80 & below

3 contact shots

Above 80 to 160 4 contact shotsXX strong 6 contact shots

6” Schedule 120 and below

3 contact shots

Above Schedule 120

4 contact shots

8” Schedule 120 and below

3 contact shots

Schedule 140 and above

4 contact shots

10” thru 24” 0.75 wall & below 3 contact shot or 1 panoramic exposures

Above 0.75 wall 4 contact shot or 1 panoramic exposures


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Above 24” All 4 contact shot or 1 panoramic exposures

15. EXPOSURE TIME CALCULATORS.The exposure time shall be calculated for the given settings by means of exposure charts or exposure scales.

16. PROCESSING OF RADIOGRAPHS:16.1 Developing time 4–8 minutes at 20 degree centigrade with

constant agitation for the first one minute and intermittent agitation there after.

16.2 After development the hanger are immersed in the stop bath (acidic acid) for 30 seconds.

16.3 Fixing the film for 5 minutes or twice the developing time, whichever is greater

16.4 After fixing, the film is to be washed for 15 minutes in clear water, and for five minutes with water which is mixed with wetting agent.

16.5 Drying shall be by either hanging for air –drying or by automatic dryer.

17.0 VIEWING CONDITIONSSubdued lighting, rather than total darkness, is preferable in the viewing room. The brightness of the surroundings should be about the same as he area of interest of the radiograph. Room


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illumination must be so arranged that there are no reflections from the surface of the film under examination. The illuminator shall be of variable intensity controlled with light diffusing glass.

18.0 ACCEPTANCE CRITERIA Acceptance criteria shall be specified in the contract or in OILSERV specifications.

19.0 PRESENTATION OF COMPLETED RADIOGRAPHS.Completed radiographs shall be arranged in sequence for each weld and enclosed with an identifying envelope stating the radiograph number, weld number, project, pipe diameter, date shot and any other information the client may require.

20.0 STORAGE OF THE PROCESSED RADIOGRAPH.Processed radiographs and report shall be delivered to the client at the end of each of day’s activity or shall be stored in partitioned-wooden storage boxes with the films placed on edge. The films shall be delivered to Oilserv representative at the end of the project.

21.0 REPORTS.The radiographic inspection report shall consist he following:Contract numberItem number, weld numberDate of testRadiographic procedureType of films / screens used.


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Curie strength / size,Development manual or automaticSensitivity obtainedNumber of exposureAccept / reject criteria STDInspection results, findingsName/signature of the interpreter/Inspection engineer

22.0 DOCUMENTATION:Report format: see CENA TECH radiographic examination report sheet.

Single wall single image multiple exposure source inside film out side

Single wall single image (panoramic)Source inside, film outside, single

exposure

SINGLE WALL, SINGLE IMAGE. SOURCE OUTSIDE, FILM INSIDE, MULTIPLE

EXPOSURESSINGLE WALL, SINGLE IMAGE (PIPE & VESSELS)

SOURCE OUTSIDE, MULTIPLE EXPOSURE

TECHNIQUE SHEET


CENA TECH

DOUBLE WALL SINGLE IMAGE, MULTIPLE EXPOSURESOURCE OUTSIDE FILM OUTSIDE

OPTICALSOURCE POSITION

SOURCE

DOUBLE WALL DOUBLE IMAGE(ELIPTICAL) TWO EXPOSURES 90 DEG

TO EACH OTHER

OFFSET

DOUBLE WALL DOUBLE IMAGE (SUPRIMPOSED MINIMUM 3 EXPOSURES 60 DEG TO EACH OTHER


CENA TECH

1010

Full penetration fillet weld

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METHOD STATEMENT FOR GAMMA RAY INSPECTION PROCEDURE.doc