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Galling of 718 threads in non-permanent connections
I have seen references to using copper coating on threads in order to reduce the galling seen in applications which require a 718 to 718 permanent connections.
I am looking for any recommendations on connections which are not permanent or even near permanent. As in connections which may be made up and broken hundreds of times in a given lifetime.
Gary Martin- Sugar Land, Texas
First of two simultaneous responses --
For plating of hardware for non-galling, I believe the gold standard is silver not copper. But if hardware must be disassembled and assembled hundreds of times, I would think that an inherently non-galling substrate would be near the top of the priority list.
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
Second of two simultaneous responses --
You're right in that copper coating and API modified dope is used on premium threaded connections made from "stainless" materials (Using stainless as a generic term for duplex & inconels etc). By far the greatest amount is plated on couplings, hangers and pup joints etc. However typically to qualify copper coating on a particular thread type, the industry has seemed to settle on achieving 10 make and breaks using min/max tolerances on the boxes and pins (ie max thread interference conditions) Which is relevant to these applications when you consider that pipe and hangers etc are only generally broken out during work overs or if there is a problem. If you're talking about premium thread type connections. I doubt whether copper and dope would withstand "hundreds of make and breaks". It looks like a test program is the only answer to assess any likely candidate coatings. For instance Electroless Nickel/PTFE composites
Regards,
Richard Guise- Lowestoft, U.K.
Years ago an Aerospace company that I worked for used a lot of copper based "anti sieze" on 718 when parts went into the oven for a "restrained " heat treatment. I can not speak to its use in the field.
James Watts- Navarre, Florida
We have coated many 718 parts in your particular industry with Nedox CR+ coating. It is a nickel based alloy that is infused with a polymer. We have also run Nedox against Nedox without galling
Corey Wesnitzer- Arlington, Texas
++++++
Sugar Blasting mating parts extends the life of screwed connections by roughening the surfaces. The roughened surface
"holds" the pipe dope so the mating parts do not meet.
Robbie Robbins
- Houston, Texas USA