SS Bolting with CS Flange

[mariolucas75]

Dear All,

Would you please advise me if it cab be used SS bolting on CS flange ?
For example on one of the plants i saw A350-LF2 flange with A320 b8m class 2 bolting.... the flange is CS and the bolting is SS...


Thank you so much
Best Regards

 

[TGS4]

Apparently you can (you saw this in a flange in an operating plant). The better question is whether you should. The answer to that is usually no. If it goes to a temperature above ambient, then SS bolts are a really bad idea...

 

[weldstan]

It was most likely used for a low temp application. I would advise against it however, especially in marine or coastal environments. Greater than anticipated tensile loads could also occur depending on the delta from tightening to low temp operation.

 

[GD2]

Not a good idea. A good idea would be to use A320 L7 Alloy Steel bolts in terms of low temperature service compatibility and strength. A320 B8M are SS Bolts and has the least strength compared to LF2 Flange. There could be chances of flange leak with these bolts from overtightening/yielding.

GDD
Canada

 

[r6155]

Without any information on the design conditions, I can't say anything. Lucubrations are bad ideas.

Regards

 

[iangineer]

I agree with the others that CS bolts should be used with a CS flange. CS bolts can work with a SS flange because bolts are more expendable and it isn't as big of a deal if they experience galvanic corrosion because they can just be changed out. SS bolts on a CS flange is typically not a good idea under normal conditions and may have been specified due to lazy or inexperienced engineering.

 

[davefitz]

The issues include (a) differential thermal expansion may loosen the bolts unless belleville washers are added (b) SCC stress corrosive cracking of some SS if the threads are lubricated with normal lubricants in steam service .

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick