Preparation of Inquiry/Purchase requisition includes preparation of Technical Requirements for Fittings. Sample Technical Requirements for a particular project is as shown below:
Applicable Codes and Standards
- Material supplied shall be strictly in accordance with the latest codes and standards, mentioned in the Material Requisition Scope of supply.
- This specification for pipes, fittings and flanges as detailed in subsequent clauses shall supplement the codes and other project specifications.
- Dimensions of butt welded fittings shall be in accordance with ASME B16.9.
- Forged threaded and socket welded fittings shall be in accordance with ASME B16.11.
- Other fittings dimensions shall comply with MSS SP-75, MSS SP-95, MSS SP-97 or BS 3799 as applicable.
- Vendor shall provide calculations as per ASME B31.3 for the fittings not covered under the above mentioned standards.
- All screwed fittings shall be threaded NPT in accordance with ASME B1.20.1.
- Union dimensions shall be in accordance with BS 3799.
- Branch reinforcing fittings (i.e. sockolets, weldolets etc.) shall be designed in accordance with the requirements of ASME B31.3. The vendor shall submit drawings during bid stage and calculations for review and approval after award of contract.
- Butt weld end preparation for pipes, fittings and flanges shall be as per ASME B16.25.
- Outside diameters and wall thickness (unless otherwise mentioned) of butt welded fittings shall be in accordance with ASME B36.10.
- All items shall be supplied in accordance with the wall thickness or schedule as stated in Inquiry / Purchase requisition. Wall thickness heavier or thinner than specified tolerance shall not be accepted.
- For all piping components, material type and grade together with NPS and schedule / wall thickness / class shall be as specified in the description within the Material requisition – Scope of Supply.
Welded Seam Components
- All welded items shall be 100% radio graphically examined to give a joint factor of 1.0.
- Pipes and fitting shall be supplied seamless unless otherwise specified.
- Seamless is an acceptable alternative for welded pipe and fittings and vice-versa are not acceptable.
Material of Construction
The chemical analysis of CS & LTCS pipes and fittings, forgings, plates shall be in accordance with the applicable product standard with the following limitations:
- Carbon 0.23 Maximum wt% (pipes)
- Carbon 0.23 Maximum wt% (forgings)
- Carbon Equivalent CE shall not exceed 0.43%
Where CE = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15
The above formula for CE is applicable when the carbon content is greater than 0.12%
- All CS & LTCS materials shall be fully killed and fine grained and shall be produced by a low sulphur and low phosphorous refining process.
- The components shall be shall be supplied in normalized or normalized and tempered condition.
- Repair welding for parent plate / weld end flange is not permitted.
- All Austenitic stainless steel, duplex stainless steel items shall be supplied in solution annealed and quenched condition as per corresponding ASTM standard.
- The carbon content of SS 316 shall not be more than 0.03%.
- All SS Materials specified as F316 / WP 316/ Type 316 may be dual certified for both SS 316 & 316L, if specifically mentioned in the project specification.
- Austenitic stainless steel shall be capable of passing an inter-granular corrosion test in accordance with ASTM A262, Practice E.
- All duplex stainless steel shall have ferrite content (volume fraction) between 35% – 65% on base metal and on heat affected zone to 35% to 70 % as per ASTM E562 four point count method.
Butt weld elbows shall be long radius type (radius =1.5 nominal pipe size). Short radius elbows are not permitted.
For reducing fittings specified with two schedules in the Inquiry / Purchase description, the first schedule refers to the larger end or run pipe, the second schedule refers to the smaller end or branch pipe.
Fittings shall be forged to the final shape and size. Fittings shall not be machined from bar stock or solid forged billets without specific approval.
Galvanizing of fittings shall be in accordance with ASTM A153. Threaded portion of fittings shall be supplied with threads free of galvanizing.
Swage nipple shall be pipe swaged by forging only. Machining of bar stock, forgings or heavy wall pipe not permitted. Dimensions shall be in accordance with MSS-SP-95.
All reduction sizes for tees and reducers to be in accordance with ASME B16.9.
Heat Treatment of Fittings
CS & LTCS fittings shall be fully killed and fine grained and shall be supplied in normalized or normalized and tempered condition.
Examination of Fittings
- 100% of CS & LTCS welded fittings, with wall thickness greater than Sch 80 shall be examined by Magnetic Particle Examination for weld bevel ends. Acceptance standards shall be in accordance with ASME VIII Division 1, Appendix 6. This shall be done after final heat treatment.
- 100% of CS, LTCS & SS forged fittings, with wall thickness greater than Sch 80 shall be examined by Magnetic Particle / Dye penetrant examination. Acceptance standards shall be in accordance with ASME VIII Division 1, Appendix 6 / 8. This shall be done after final heat treatment.
- 100% of SS & DSS wrought fittings having wall thickness more than 20mm shall have the bevel and weld end over a width of 25mm, examined by Dye penetrant Method. Acceptance standards shall be in accordance with ASME VIII Division 1, Appendix 8.
- 100% of DSS welded fittings with a wall thickness greater than 30mm shall be 100% ultrasonically examined in accordance with ASME VIII Division 1.
- 100% of DSS forged fittings weld bevels shall be examined by Dye Penetrant inspection.
Sour service requirements
- All materials specified for sour service shall, as a minimum, meet the requirements of NACE MR0175 / ISO 15156 – latest edition.
- All welded pipes / fittings in sour service shall be HIC tested, if required by the project specification. It shall be conducted for one pipe / fitting per heat in accordance with NACE TM-0284 Solution – A with acceptance criteria as specified in NACE MR-0175.
Positive material identification
Positive Material Identification (PMI) shall be conducted for all SS / CRA alloy piping items as per the project specification included in the Inquiry / Purchase requisition.
Impact test requirements
- All CS, LTCS, welded austenitic and duplex stainless steel piping components shall be impact tested in accordance with ASME B31.3.
- For carbon steel pipes and fittings, the impact test temperature shall be the ‘minimum metal temperature’ as defined in the project. The impact test requirement and acceptance criteria shall be as per Cl. 323.2.2 and Cl. 323.3.5 of ASME B31.3 respectively.
- For LTCS items, the impact test temperature shall be (-460C). Test results shall be atleast 27 joules as an average of three tests (for standard specimen 10 x 10 mm), oneresult may be lower, but not lower than 21 joules.
- For welded SS and DSS items, the impact test temperature shall be the ‘minimum metal temperature’ as defined in the project but not more than (-1010C) and (-500C) respectively. For SS items, the acceptance criteria shall be as per Cl. 323.3.5 of ASME B 31.3. For DSS items, test results shall be at least 40 joules in transverse direction (for standard specimen 10 x 10 mm) as an average of three tests, one result may be lower but not less than 30 joules.
Inspection & Testing
- All items shall be inspected and tested in accordance with the relevant product standard and as stated in the Purchase requisition.
- Pressure testing of stainless steel products where required by the standard shall be performed using water having less than 30ppm of chlorides.
- All welds in pipes & fittings shall be 100% radio graphed in accordance with the individual ASTM Standard.
- Ultrasonic examination in lieu of radiography is not allowed.
- Examinations and / or tests may be reviewed and / or witnessed by the contractor or their authorized third party inspector at the vendor’s facility.
- The vendor is responsible for informing the contractor about the availability of goods for inspection and testing.
- Inspection shall be performed as per “Vendor Quality Requirement form” attached with the Inquiry / Purchase requisition.
- The manufacturer shall submit the certificate of conformity of the material duly certified by inspector.
Marking and Color Coding
- Marking of the piping components shall be done as per applicable codes and standards.
- In addition to piping item/part number, purchase order number specified in Material Requisition Scope of supply.
- For the material specified as sour service, LT, CRYO in Material Requisition Scope of supply, the marking shall include “Sour”, “LT”, and “CRYO” respectively.
- If punching or die stamping is used for carbon, low temperature and alloy steel, the stamps shall be of low-stress stamps (dot or round bottomed).
- For stainless steel stamping shall be electro etched.
- If stenciling is used, it shall be done by indelible paint.
- For sizes below 1.1/2” and below the markings shall be done on attached metal tags.
- Colour coding of piping components shall be done based on the material categories as identified in project specification attached with Inquiry / Purchase requisition.
Packing and Preservation
- Material shall be packed ready for export in a manner which allows easy handling and prevents damage.
- Vendor shall submit their standard packing procedure to purchaser for approval.
- Open ends of fittings and flanges shall be supplied with heavy duty plastic protective plugs or caps. For beveled ends, the caps shall protect the full area of the bevel.
- Water proof barrier material shall be used for stainless steel materials to protect against chlorine attack by exposure to salt water atmosphere.
- Carbon steel and stainless steel items are not allowed to be stored together and shall be packed separately.