Thaksen,
I am referring to same Aramco spec 2005 version. The extracts from this spec are as below.
32-SAMSS-004, gives the choice between SA 350LF1 or LF2 or SA266 Gr-4. Grade 350LF1/LF2 materials are better materials with respect to SA266, as it’s designed for low temperature and with notch toughness requirements and produced with better steel metallurgy..
32-SAMSS-004. Clause 12.2 specifies that sour services materials should meet requirements of Aramco engineering standard SAES-A-301. Grade 350LF1 /LF2 due to better metallurgy aspects is accepted by this standard for sour service, while SA 266 is not.
Also SA 350 specification does not impose any restriction on sizes of forgings(350 LF1/LF2) to be produced, other than limited by manufacturer’s capability.
My feel is if the service is sour service and if cost is not a factor (for 24” O.D), you may approach your client about staying with SA 350.For non-sour services SA-266 should be fine. The rationale is essentially cost.
SA 266 is just identical to ASTM A 266. For your reference I’ve attached extracts from SA 266 & SA 350.
There’re some reservations forms NACE on acceptance of this material (SA-266) for sour service environment.
Thanks
A) Materials for hydrogen service shall be selected in accordance with API PUBL 941 using a value for the hydrogen partial pressure 10% above the design partial pressure and a temperature of 30°C above the design temperature.
B) Materials for pressure vessels in amine service shall be selected in accordance with Table 1 and API RP 945.
C) Materials for pressure vessels for de-aeration service shall be in accordance with Table 1 and NACE RP0590.
D) Materials for vessels in environments specified in paragraph 12.2 of this specification with normal operating temperatures up to 150°C (302°F), shall be in accordance with Table 1, with the following revisions:
i) Forged flanges and forged fittings are restricted to: SA-350 LF1 or LF2 or SA-266 Grade 4. Flanges above 24-inch diameter shall be SA-266, Grade 4.
ii) Studs and nuts are restricted to: SA-193 B7M or L7M and SA-194 Grade 2HM.
iii) It shall satisfy the requirements of SAES-A-301 and NACE RP0472.
iv) Shells and heads formed from plate shall be manufactured from HIC resistant steels that meet the testing requirements of 01-SAMSS-016.
v) Piping components used in the manufacture of a pressure vessel within the scope of this specification shall be
manufactured from HIC resistant steels that meet the testing requirements of 01-SAMSS-016.
E) Low alloy steels shall not be mixed, i.e., a vessel requiring 1-¼ Cr-½ Mo materials shall have all components manufactured from 1-¼ Cr-½ Mo.
F) Low alloy steels shall be specified in the normalized and tempered heat-treated condition.
Paragraph: 12.2-HIC Resistant Materials
Hydrogen Induced Cracking (HIC) resistant steel qualified in accordance with 01-SAMSS-016 shall be specified for the following environments with normal operating temperatures between 0°C (32°F) and 150°C (302°F):
a) Sour water service with a hydrogen sulfide (H2S) concentration above 2 mg/L (2 ppm) and a total pressure of 400 Kpa absolute (65 psia) or greater.
b) Hydrocarbon services meeting the definition of sour environments in SAES-A-301, where the H2S concentration of 2 mg/L (2 ppm) or more in the water phase is equivalent to H2S partial pressure of 0.05 psia.
c) A hydrocarbon system exposed to an environment with a H2S concentration above 50 mg/L (50 ppm) in the water phase, regardless of H2S partial pressure.
EXTRACTS ON SA-266, FLANGES
SA 350, LF1/LF2-EXTRACTS
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of THAKSEN INGOLE
Sent: Thursday, September 16, 2010 2:29 AM
To: material welding
Subject: [MW:7037] A-266 grade for Sour service
Dear Colleagues
As per 32-SAMSS-004, table 1,general notes D states that " Material for vessels in environment specified in paragraph 12.2 of this specification with the normal operating temperature up to 150 deg C shall be in accordance of table 1 with the following revisions(there are many points one of them is below)
1) flanges above 24" should be SA-266 Grade 4
Paragraph 12.2 speaks about HIC requirement for sour service.
My query
1) Why is this special requirement for flanges only above 24"
2) The SA-266 is not listed in B16.5 then how it is written as SA-266 it is just an A-266 with Grades 1,2,3.4
3) Can some one forward me the A-266 & MR0103 specification as to know what is exactly written in it.
Regards
Thaksen
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