Fastners subjected to SOUR service (not exposed bolts) requires bolts to be heat treated to have hardness values within the limits of NACE MR 0175. However such bolts are of the intermediate to low strength. The use of these bolts are restricted by B16.5.
ASME B16.5 states, "These bolting materials may be
used
with all listed materials and gaskets, provided it has
been verified that a sealed
joint can be maintained under rated working pressure
and temperature."
Many piping classes used for SOUR service use the B7M, B8M bolts.
It appears that a flange calcualtion is to be done to verify the gasket seating with the lower strength bolts. If the bolt load turns out to be less (at the allowable stress stated by ASME B31.3 Table A1) than required by the gasket seating and at the flange rating pressure. The bolt size cannot be increased.
Is it required to verify this by calculation or is there something that is implicit, to let these bolts be used within the pipe classes.
This was posted earlier too. But received no response. Think it was because it was added to another post on "bolt thread engagement".
Sajit
This archive was generated by hypermail 2.1.8 : Mon Oct 27 2008 - 20:24:08 EDT