Stainless Steel Bolts vs Epoxy Coated bolts

[rzjim]

I have to write How to Install Manual and a Material Specification for couplings in our water distribution system. A problem I am having is what materials the coupling and bolts should be made from. I prefer ductile iron center and end rings with stainless 304 bolts and nuts. I also have to require North American made or meets intent of American Recovery and Reinvestment Act (ARRA). Most cast products are made overseas. Larger couplings are only avaialble in steel. Construction crews hate stainless becuase the nuts and bolts gaul. We require anti-gauling lubricant, but they still sieze. I think the crews use air wrenches. Should I require all steel couplings with epoxy coating? Should I stick with 304 stainless or look into the epoxy coated steel bolts? thanks in advance - Jim

 

[bimr]

My vote is for the stainless. The epoxy does not seem to stand up to the physical damage when the bolts are installed.

 

[rconner]

There is a standard ANSI/AWWA C219-06 Bolted, Sleeve-Type Couplings for Plain-End Pipe that contains requirements for bolting of such (normally types of steel). Several specific options are mentioned for these couplings, as well as other guidance.

Bolting requirements for standardized ductile iron mechanical joint piping, e.g. “MJ sleeves”, are included in ANSI/AWWA C111/A21.11-07 Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings. Per the latter, I believe “alloy steel” bolts have most often been furnished over the last several decades per this specification. Along with formidable mechanical properties (and I believe non-galling nature), the most often supplied C111 bolting requires a specified chemistry of the alloy steel, in that a minimum amount of nickel, copper, and chrome must be added to that steel to create a slight though normally dependable cathodic relationship. I believe this relationship is designed/intended to harm neither the bolts nor sleeve for that specific standardized application.

All this being said, I suspect many users have also employed basic carbon steel bolts and rods etc. for many years for piping applications underground, and maybe even with some degree of success, though I suspect same could most normally be accompanied also with use of heavy/effectively field applied mastics or other protection/encasements etc. for any potentially corrosive environments.

 

[turbzero]

Try using different grade stainless for the nuts and bolts (eg 316 for the nuts and 304 for the bolts) - the contractors will be happier with less gauling..

 

[stanier]

turbzero,

This is a falacy long proven to not be factual.

Why not stick with carbon steel fasteners and coat them in grease then wrap them? check out other industries such as petrochem and off shore oil & gas. You will fond the most common material is ASTM A 193 carbon steel studs.

Austenitic stainless steel such as type 304 is not a listed materail in ASME B16.5. Any flange using austenitic stainless that is not strain hardened needs a design calculation as the standard design rating does not apply.

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[bimr]

If an austenitic bolt such as 304 or 316 is used, then galling could be minimised by using a hard nut of duplex stainless steel or martensitic 431 stainless steel.

It should be noted that while using 304 bolts with 316 nuts is often quoted as a cure for galling, the hardness difference is not necessarily sufficient to prevent galling even with a cold rolled, harder 304 thread used against an annealed, softer 316
nut.

http://www.assda.asn.au/images/PDFs/faq no5 galling.pdf