Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
(OP)
I'm now completing my Nth failure investigation of ASTM A193 Gr. B7 studs that suffered sulfide stress cracking. Client will of course go to grade B7M to avoid SSC, but that doesn't address the issue of corrosion pitting severe enough after one year to render the studs unserviceable.
Any suggestions that preferably avoid the austenitic stainless grades? I'm not necessarily looking for infinite service life; 3~5 years would be nice.
Any suggestions that preferably avoid the austenitic stainless grades? I'm not necessarily looking for infinite service life; 3~5 years would be nice.
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"





RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
Duplex should either be lightly cold worked or annealed (it looses ductility when heavily cold worked)
If I went beyond those I would go straight to MP35N
I have has some poor experience with 718 fasteners.
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P.E. Metallurgy, Plymouth Tube
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
The exchanger is laid up seasonally in a Great Lakes climate. Not sure of the details of the protective cover but I suspect it isn't much different than a tent. I believe it is bad actors dissolved in condensing atmospheric moisture that is causing most of the attack. I view the two damage mechanisms as separate although having probably a common corrodent. The sulphide spot test on the cleaned threads was positive for both colour and odour.
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"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
"If you don't have time to do the job right the first time, when are you going to find time to repair it?"
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
Another option (assuming you don't have chlorides) is A453-660. It is listed in NACE MR0103, but not in MR0175 (the difference being chlorides). It will be cheaper than a lot of the other materials and actually has an ASME bolt spec, which makes it easier.
SJ, I would be interested to know of any published references regarding Moly Disulphide causing SCC. The basis for that statement is usually work done by the nuclear industry in the US and has been subsequently questioned by other researchers who looked at the same failure. A lot of "Moly" anti-seizes don't actually contain much Moly Disulphide and they have been very widely used in industry (refining in particular) around the world without identified incidents of late.
RE: Alternative Alloys for Grade B7M Heat Exchanger Studs in Sour Service?
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.