Hi All,
I have concern over using A193 B7M in sour services pipe specs.
There is excerpt in ASME B16.5 which says:
5.3.3 Intermediate Strength Bolting. Bolting materials listed as intermediate strength in Table 1B, and other bolting of comparable strength, may be used in any flanged joint provided the user verifies their ability to seat the selected gasket and maintain a sealed joint under expected operating conditions.
5.3.4 Low-Strength Bolting. Bolting materials having no more than 206 MPa (30 ksi) specified minimum yield strength are listed as low strength in Table 1B.
These materials and others of comparable strength are to be used only in Class 150 and 300 flanged joints and only with gaskets described in para. 5.4.2. Flanged assemblies using low-strength carbon steel bolts should not be used above 200°C (400°F) or below −29°C (−20°F).
and the excerpt from NACE MR0175 which says :
A.2.2.4 Bolting and fasteners
Bolting that can be exposed directly to a sour environment, or that is buried, insulated, equipped with flange protectors or otherwise denied direct atmospheric exposure, shall conform to the general requirements of A.2.1.
Designers and users should be aware that it can be necessary to lower equipment pressure ratings when using SSC-resistant bolting and fasteners. The use of SSC-resistant bolting and fasteners with API flanges shall be in accordance with ISO 10423. Table A.4 - Acceptable bolting materials
My concern:
Like for low strength bolt material, it can be used for only
class 150# and 300# only. Is there any way to de-rate the pressure rating of
ASME B16.5 while using the intermediate strength material A193 B7M, though the
code allows to use intermediate strength material for full flange rating of
ASME B16.5.
Issue arises when my client specification says as below
while using A193 B7M material for sour service :
- Design limits acc. to ASME B16.5 flange rating mat. grp
1.1, and limited by allowable stress of
bolting material
Please share your understanding on this.
Many thanks in anticipation.
A193 B7M Bolt Material
Re: A193 B7M Bolt Material
