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Galling of Stainless Steel Threaded Plugs

Galling of Stainless Steel Threaded Plugs

Galling of Stainless Steel Threaded Plugs

We have a number of 2205 duplex heat exchangers in our facility that have 316 stainless steel threaded plugs incorporated into their design.  These exchangers operate at approximately 300°F, is anyone aware of experiences whereby plugs in this type of service leak?  Also, Does anyone have any experiences with galling between a 316 stainless steel plug and duplex steel plate?  Any suggestions with respect to torquing?


RE: Galling of Stainless Steel Threaded Plugs

2205 SS is notorious for it propensity to gall, even with the more galling resistant materials.  One of the worst situations is in a pipe plug, basically because of its design.   

316 SS vs 2205 SS has a threshold galling stress of 2 ksi.

2205 SS vs Nitronic 60 SS has a threshold galling stress of 30 ksi where 50 is consider very low galling tendencies.  Depending on the enviroment this may be solution.

I don't have the self-mated numbers but would imagine that it very low.

What is the enviroment that the materials are seeing?

RE: Galling of Stainless Steel Threaded Plugs

You should use an anti-sieze.  Make sure that it is compatable with your process.  I like the ones based on synthetic greases.
2205 is a bit better than 316 at gall resistance, but they are  rather bad.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

RE: Galling of Stainless Steel Threaded Plugs


the service environment for these exchangers is primarily a combination of light hydrocarbons, hydrogen, H2S and water.

RE: Galling of Stainless Steel Threaded Plugs

For what it's worth, over the years I've had good success with milk of magnesia as an anti-sieze.  

RE: Galling of Stainless Steel Threaded Plugs

Sorry for the delay in getting back.  Had a few distractions along the way.
I think you could use a Nitronic 60 SS plug in your case, I certainly would try one or two.  Not gall proof but a lot better than other combinations.
I'm also looking for a good combination where you might use a bushing of a different material that would have less tendency to gall with a pipe plug of still another material.
I have used this approach in the past. The H2S makes this a little tougher.  

Although milk of magnesia is good anti-seize under certain conditions I would not use it in your case being that you have a slightly acidic solution containing chlorides.  I would be a little afraid of the formation of magnesium chloride in some crevices.   

Here is one that I’ve used with very good success in similar environments.

Therm-O-Plate 110

RE: Galling of Stainless Steel Threaded Plugs

The folks at www.fastorq.com, since they are in the bolting business anyway, developed an anti-sieze that I saw demonstrated at their place in Houston 4-5 years ago, and I was, to put it simply, danged impressed.

I had previously had enough experience with galling of SS nuts and bolts on a variety of equipment from turbine bolting to Hx's to know the problem, and the commercial anti-sieze's available on the market, and to know that the demonstration was bona-fide and the results were real and quite impressive.

Given your problem, that is the first place I would go to find a solution.

They had a MSDS sheet on the stuff, so you can see what is in it, but not how it is formulated.

I will leave it to you to search their site for this product, or contact them for specific info.


RE: Galling of Stainless Steel Threaded Plugs

I did go to the site after posting above, since I had not visited in a while, and under lubricants, it is the fastorq A/G that I referred to in my last post.


It fits within your temperature requirement.

Good luck


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