API 6A Stud bolt grade for SOUR service 1

[svi]

Table 49 of API 6A 2004 lists bolts grades for material classes DD to HH (SOUR service classes) as follows,

B7 for non-exposed flange joints
B7M for exposed flange joints

Should this not have been the other way? B7 for the exposed bolts. It is desirable to have high strength B7 bolts for the joint when the service allows. The requirement of NACE SOUR environment should apply for the non-exposed bolts? In the column heading of the table 49 it is written as 'Exposed (Low strength)'.

 

[SJones]

'Exposed' means exposed to the H2S environment, in which case the lower hardness is required.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[jbeckhou]

the M stands for modified, which they heat treat the bolting to meet the requirements for NACE hardness.

Petrotrim Services

http://www.petrotrim.com