ASME B16.5 SS fasteners & stub ends rating 1

[stanier]

My question relates to the use of stainless steel stud bolts for ASME B16.5 flanges. Application temperature is < 100C

I have been advised that this standard requires that for flanges using other than listed high strength bolt materials that flange calculations are necessary. Whereas A193 studs are high strength, CF8M ss materials are listed as intermediate strength.

Does this mean that the standard flange classes 150,300, 600 etc are down rated when ss fasteners are used?

Has some body already done the calculations before?

Can stub ends with backing flanges be used for Class 600 at 100C?

Can A193 grB studs be hot dip galvanised without reducing their strength?



Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[gr2vessels]

Hi stanier,

It's unusual to re-calculate B16.5 flanges, in any class however, if you are using the full strength of the bolts, you could extrude the gasket if unsuitable for the flange ratingor even bend the flange usin a too hard gasket. That is the only time you would check the gasket seating stresses and the flange bending stresses. Basically, for what you require, the stainless steel bolting is related to the corrosion resistance properties, not to the strenght (refer NACE requirements for various corrosive environments). For standard applications (I'm assuming that is your case), the bolting strenght of B7 or B8M or the like is not an issue you have to consider, ie no downrating is required for any flange class, provided the flanges conform to B16.5 or B16.47 of their class.

Yes, where required, the bolting calculations have to be done per ASME or similar code for pressure vessels or pressure piping. These calculations, where required, are important and have legal ramifications, related to the safety of your pressure system.

I'm not sure what are you refering to over stub end with backing flange, is it lap joint flanged connection?

Yes, these days the B7 bolts can be galvanised or hot dip galvanised, provided the supplier of galvanised bolts can supply written guarantees that the bolts have not been subjected to Hydrogen embrittlement. Please note that not many bolt manufacturers have this process under control. The bolts fabrication has to account for the thickness of deposited Zinc material, whilst maintaining the listed strenght.

Cheers,

gr2vessels

 

[stanier]

Hi Gr2 Vessels,

The reason I posed the question is that I had an opportunity to read B16,5. I never had before and in there it can be read that ss bolts are of intermediate grade and that the flange rating is based on high strength (B7) bolts. Ergo a flange design has to be carried out for a ss bolted flange. This would also apply to a ss wnrf flange. This is not something I had encountered.

Yes lap joints or MSS 143 stub ends is what I had in mind.

I was hoping one of the code committtee members would pick this one up and give us a lesson.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au