Fastener Materials for FGD Lime Slurry

[geesamand]

Hello all.

My company produces some equipment for working in FGD limestone slurry tanks. Our design group has a pretty good handle on base material options (316, 2205, 254SMO, AL6XN, C-276), but we're less adept with fastener materials. I see that Alloy 686 is possibly the highest performing choice, suitable for use with C-276. I've not seen much aside from 686 w.r.t. 686, presumably since so many parts are fabricated.

What less expensive materials might also be suitable for use in less aggressive slurries?

Thanks in advance.

David

 

[EdStainless]

In general you need to make you fasteners out of an equal or slightly better alloy than your base material. Some alloys are easier to make into bolts than others.
Personally I would not use anything lower than 2205, no 3xx stainless ever.
Availability will probably be the biggest issue. And remember in bolts you want rolled threads, not cut, if possible.
I have seen plants that only use 2205 and one of "C" alloys (686, C-22 or 59). Only two options, less risk of a mix-up.

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[unclesyd]

I was on the phone while my fastener buddy while reading this thread and posed the question on delivery on 2205 fasteners, both studs and bolts.

These are available in 2-3 wks on sizes under 1 1/8" while larger sizes are 6-8 wks. He also mention that on the higher alloy materials that quantity was becoming a factor as no one is stocking a lot the exotic blanks as was the case a year ago. Again quantity will determine whether you can get rolled or single point threads in a short time. The other alloys mentioned for fasteners are at the present rare as hen's teeth. Any of these alloys would take long lead times.

 

[geesamand]

I did get in touch with a high alloy fastener supplier.

They said basically the same thing: for my 3/4" HHCS it was 1-2wk delivery in C276, 2205, or AL-6XN. Alloy 686 is sold exclusively by one fastener supplier so I shouldn't plan on getting that cheaply or readily.

So I have inferred that it's best to design the fastener out of the same material as the base stock. (Rather than 'rounding up' to some higher alloy that might be produced in higher quantities).

Dave

 

[Stl63]

I would take a look if you really need stainless steel bolts, such as duplex 2205 or Nickel based C276. I've seen a dozen Limestone slurry storage tanks, and not one was made from stainless steel. Not sure what "Edstainless" is basing his judgement of no less than 2205. He doesn't know temp., ph, or any chem. composition factors of the fluid.
If your an equipment vendor or even suppling manways, all external to the vessel, carbon or low grade 304 is adequate. If your internal on an agitator blade, let's say, then yeah a higher grade of SS is necessary. Crevice corrosion can be a real problem, thinking of sealing a bolt nut if possible is a good idea.