Valve Material requirement of carbon steel, austenitic stainless steel, duplex stainless steel, 17/4 PH stainless steel, soft seat and seal material (Part 1)- Executed project-SGPK03
1.Carbon Steel and Impact Tested Carbon Steel
The chemical composition of carbon steel castings and forgings shall be limited as follows:
Carbon content 0.22% max
Carbon equivalent 0.43% max by ladle analysis where :
CEV = C + Mn/6 + (Cr+Mo+V)/5 +(Cu + Ni)/15
NACE MR0175 specified material shall also have limitations on chemical composition as follows :
Sulphur : 0.010% max.
Phosphorous : 0.030% max
Manganese : 1.30% max
All castings for sour service (NACE MR0175) and impact tested carbon steel castings shall be suitably heat treated after all welding operations have been performed. This requirement also applies to the weld repair of defects irrespective of size.
All ASTM A105 materials shall be supplied in a normalised condition. Sheet 5 of 15.All impact tested carbon steel to ASTM A350 LF2 shall be Class 1.
2.Austenitic Stainless Steel
Austenitic stainless steel shall be supplied in a solution annealed condition. Solution annealing shall be carried out after all welding operations have been performed including any Purchaser permitted weld repair.
Butt weld valves and SP items specified as 316/316Lstainless steel shall be supplied dual certified ie. having the mechanical properties of 316 SS and the chemical composition of316LSS.
3. Duplex Stainless Steel
Duplex stainless steel shall be supplied in a solution annealed condition. Solution annealing shall be carried out after all welding operations have been performed including any Purchaser permitted weld repair.
Micrographic examination shall be carried out. The ferrite content shall be determined in accordance with ASTM E562 or equivalent, and shall be between 40% and 60% in the final delivered condition. The microstructure, as examined at 500 X magnification on a suitably etched specimen, shall be free from intermetallic phases and precipitates.
Charpy impact testing is required for cast duplex stainless steel in accordance with ASTM A370 at minus 46 Deg C. The minimum absorbed energy values shall be 45 Joules min average, 35 Joules min individual. Hardness testing shall be carried out, hardness being 28 HRC max The testing frequency for the above tests shall be per heat and treatment batch.Cast duplex valve and SP items bodies shall have a pressure / temperature rating in accordance with ASME B16.34 material group 2.8.
4. 17/4 PH Stainless Steel
Impact testing is required for 17/4 PH stainless steel with a minimum design temperature, stated on the valve and SP item data sheets, below minus 9 Deg C.
Impact testing shall be carried out in accordance with ASME B31.3 at minus 46 Deg C.
The minimum transverse absorbed energy values for a10mmx10mmspecimen shall be 38 Joules min average, 28 Joules min individual. Minimum lateral expansion shall be0.38mm.17/4 PH SS is not an acceptable alternative to 316 SS where valve or SP item body is 316 SS.
5. NACE MR0175 Requirements
Valves and SP items specified to NACE MR0175 shall be certified as meeting all
requirements for all parts which can be contacted by the sour environment. All materials shall be fabricated, tested and inspected in accordance with the requirements of NACE MR 0175.
Cast duplex not listed in NACE must be qualified and certified for use in sour service,with the requirements and hardness of wrought duplex UNS S31803 (28 HRC) being met. Testing shall be carried out in accordance with NACE MR0175-2001, test level IV,at a pH of 3.5 and temperatures of 90 Deg C +/- 5 Deg C and 150 Deg C +/- 5 Deg C.
Vendor shall also submit any previous qualification data with bid, together with sour
service history for material, from casting source offered.
6. Amine Service Requirements
In addition to the requirements of point 1, carbon steel and impact tested carbon steel valves and SP items, specified for use in amine service, shall have all welds stress relieved by post weld heat treatment. The weld heat affected zone hardness shall beless than 248 HV10.
Copper and copper based alloys, monel and aluminium alloys shall not be exposed to amine service.
7. Soft Seat and Seal Materials
All seat and seal materials shall be suitable for the maximum design conditions and
service fluids stated in the Valve and SP item Data Sheets, with material data sheets, detailing pressure / temperature capabilities, being submitted with bid. Materials in hydrocarbon gas service shall be resistant to explosive decompression. Suitability for amine service, where required, shall also be considered.
Vendor shall note all valves and SP items may be subjected to periodical dilute
methanol exposure due to process line methanol injection for hydrate removal.
8. Welding and Weld Repairs
Weld repairs are permissible for castings only, forgings shall not be weld repaired. No weld repair shall be completed until Purchaser approval of procedures has been obtained.