Galling of Stainless Steel Threaded Plugs 2

[alloy2205]

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?


Sincerely,
Alloy2205

 

[unclesyd]

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?

 

[EdStainless]

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.

http://www.trenttube.com/Trent/tech_form.htm

 

[alloy2205]

unclesyd,

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

 

[weldtek]

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

 

[unclesyd]

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

http://www.socousa.com/showprod_detail.asp?pid=878&type=cat&id=2&prid=104

 

[rmw]

The folks at

http://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.

rmw

 

[rmw]

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.

http://www.fastorq.com/lubes.htm

It fits within your temperature requirement.

Good luck

rmw