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.

Closing

1.0 CLOSING:

1.1 The process starts with issue of work allotment card to supervisors to closing section.

1.2 Take the moulds and cores which are checked and cleared by supervisors for closing.

1.3 Arrange the position of moulds and required cores of the running melt in a transverse line. The same is to be confirmed by the supervisors.

1.4 For moulds and cores the following activities are to be carried out prior to the coating.
1. All gas venting are opened.
2. All loose sand is removed and cleaned.
3. Necessary repair work is carried out.
4. Proper dressing is done around the chills placed area.

1.5 Zircon-thinner base coating is given for Carbon-di-oxide and Sodium silicate mould/core and shell mould/core. Zircon-water base coating is given for phenolic/ no-bake mould/core.

1.6 1) Heat all small and medium cores (UP to 50 Kgs) to drive out moisture in the core oven for 200°C to 300 °C temperatures and for 20 to 30 minutes time. All bigger size (above 50 Kgs) cores are to be heated by hand burner for 2 to 3 minutes approximately.

 2) All moulds are to be heated by hand burner for 2 to 3 minutes approximately.

1.7 Carry out following work on all moulds/cores, after heating process.
 1) Clean all loose burnt sand in the edges.
2) Uneven coatings of the surface are to be removed by brush
  for smooth surface.
3) Final cleaning to be done by blowing compressed air.

1.8 The core hollow in all the heated cores are to be filled-up with green sand or loose sand.

1.9 All cleaned and coated cores are to be assembled in the mould
  and the same are to be confirmed by supervisor responsible.

2.0 After assembling the core, final cleaning is to be carried out by compressed air.

2.1 Moulds are to be closed and clamped by suitable bolts and nuts, preferably bolts and nuts 5/8” size.

2.2 i) All sample moulds are to be re opened and cleaned with  
  Compressed air and closed again.
  ii) Regular production moulds are reopened and closed randomly

2.3 All closed moulds are to be packed with carbon-di-oxide + Sodium silicate at the parting line to avoid possible metal leakage.

2.4 Avoid closing of more than two customer’s items moulds in one particular melt, preferable the whole melt is to be taken for one customer.

2.5 Required keel block mould to be kept ready for each heat and keel block to be poured with out fail.

Core Making

1.0 CORE MAKING:

1.1 An instruction starts with issue of allotment card from production supervisors to charge/hand to core makers.

1.2 Check allotment card for description Model number and customer name. Supervisor is responsible for referring this with the core box issued.

1.3 Clean core box before starting core making.

1.4 Before filling the sand in core box, check whether placement of zircon sand, chills, proper reinforcement, Gas venting are done as per the instruction written on the core box.

1.5 Cores are to be made hollow as per instruction written on the core box. If there is no instruction on core box, the same is clarified with supervisor if required.

1.6 Care is to be taken by core- maker, to avoid loose ramming over gassing in case of Carbon–di-oxide and Sodium silicate cores.

2.0 POST – CORE MAKING:

2.1 Check the hardness by Hardness tester in case of Carbon-di-oxide and Sodium silicate after core making.

2.2 Ensure proper setting time and curing in case of phenolic/no bake process i.e., curing time 6 to 8 hrs, minimum. To ensure proper curing, use cores made in a shift after a gap of one shift.

2.3 Check surface finish for roughness and loose ramming.

2.4 Ensure proper storage of cores.  

2.5 The post- core making activities procedure is to be checked by the supervisor.

2.6 After above are completed, core is to be identified with date.

Moulding

1.0 MOULDING

1.1 Process starts with issue of allotment card from production supervisor to Moulding batches.

1.2 Allotment card is checked by the supervisor for the drawing number or pattern number and size with reference to the planning sheet and pattern issued.

1.3 Pattern is to be cleaned before starting Moulding.

1.4 Moulding box is suitably checked prior to Moulding. While Moulding with loose patterns, most    economical box is to be used.

1.5 Before filling the sand in mould check the placement of risers /runners,chills and spruces are    placed as written on the patterns.

1.6 Check and confirm required quantity of facing sand, backing sand and Zircon sand is used as  per standard instructions given below.

1. Zircon sand, wherever marked with dotted area only on pattern and core box.
2. Facing sand approximately 2" thick on the surface of the pattern.
3. Remaining backing sand for bottom moulds and top moulds.

1.7 Take necessary care to avoid loose ramming and over gassing of mould.

2.0 POST MOULDING:

2.1 Check mould hardness at random after 30 minutes of making the mould. Record the hardness in Moulding check list of production log sheet.

2.2 To possible extent, avoid repairs.

2.3 Check surface finish by roughness of mould surface.

2.4 Avoid stacking of more than 4 moulds.

2.5 Supervisor to check and ensure the above instructions are followed.