Non-destructive Testing

RADIOGRAPHY

1.0 PURPOSE:  

This procedure is issued to provide guidelines on conducting Radiography examination and interpretation of Radiography films.

2.0 SCOPE:

 This procedure covers the radiography examination of steel castings at Flow Link Systems or at Subcontract end.

3.0 APPLICABLE SPECIFICATIONS:

1. ANSI B 16.34 Annex ‘B’ for acceptance criteria
2. Ref Radiographs ASTM E446
3. Ref Radiograph ASTM E186
4. ASME Section V Article - 2

4.0 QUALIFICATION OF PERSONNEL FOR RADIOGRAPHY EXAMINATION:

4.1 The personnel employed for conducting the examination should be qualified as per SNT-TC-1A recommended practice at least level I.

4.2 Personnel evaluating the radiography film should be competent and Level II qualified as per SNT-TC-1A.

5.0 CASTING SURFACE REQUIREMENT:

Casting shall have smooth surface which are free of loose sand, oxides, scales and surface irregularities.

6.0 SOURCE OF RADIATION:

 Ir 192 are used for TK up to 3½”.

Co 60 are used for TK up to 4½”.
The recommended min wall thickness to be radiographed are 0.75” for steel castings by Ir 192 source and 1.50” for Co 60 Source.

6.1 The minimum recommended thickness limitation may be reduced when the radiographic techniques used demonstrate that the required radiographic sensitivity has been obtained.

6.2 The direction of the central beam of radiation is centered on the area of interest whenever practical. 
 
7.0 FILMS:

7.1 Commercial fine grained radiographic films equal or fine grained than type 2 of ASTM E94 are used.

7.2 Preference is given for usage of D4 films for thicknesses up to 0.75” and D7 films for thicknesses above 0.75”. Both D4, D7 films are used for composite film technique.

7.3 It is ensured that the film is placed as close as practical to the part being radiographed.

8.0 SCREENS:

8.1 Any available intensifying screens except those of a fluorescent type are used. Lead intensifying screens of 0.005” thick in front and 0.010” thick in back are used.

8.2 It is ensured that the screens are free from scratches, wrinkles, pits and oxide coating.

8.3 As a check on back scattered radiations, a lead symbol B with minimum dimensions of 0.5” in height and 0.0625” in thickness is attached to the back of film holders.

9.0 IMAGE QUALITY INDICATOR:

9.1 Penetrameter meeting the requirements of ASTM E142/ DIN 54109 is used.


9.2 IQI’s are placed on the source side of the part under examination. Where this is impractical, the IQI is placed on the film side and a lead letter F is placed along side the IQI. For continuous circumferential radiography, at least one IQI at 120° interval is used.


10.0 IDEBTIFICATION:

10.1 All films bear identification markers to properly orient the film for interpretation and to denote the actual part under examination.

10.2 Films are provided with folders, duly marked to identify the organization producing the radiograph and the date of exposure.

10.3 Each part radiographed is stamped with unique number on casting which will appear on the film to correlate.

10.4 Re shoot radiography after repair is identified by ‘R’ letter next to the RT No.

 Eg.: RT XX – R (For reshoot after 1st Repair)
  RT XX – R1 (For reshoot after 2nd Repair)


11.0 RADIOGRAGHIC TECHNIQUE:

11.1 Technique and information regarding thickness, SFD, etc, Shooting sketches prepared by the manufacturer or prepared by radiography subcontractor, competent person and approved by manufacturer are used.

11.2 A single wall exposure technique is used for radiography whenever practical. When it is not practical to use a single wall technique, a double wall technique is used. 


12.0 DENSITY:

12.1 It is ensured that Radiographs are within the following photographic density range.

a) Single film viewing – 1.5 Min, 4.0 Max.
b) Super imposed viewing of double film, each size film – 1.0 Min, 2.5 Max with a double film – 4.0 Max.