stainless parts "locking up" - high temp/pressure... any ideas?
stainless parts "locking up" - high temp/pressure... any ideas?
(OP)
Everything is 304SS. We test the pieces at 1750F for about 3 hours. We have a male piece with 1 1/4-12 class 2 threads and then a nozzle sits on top of the male piece. On top of that is a cap nut that screws down around the nozzle on the 1 1/4 threads and then clamps the nozzle down so that the nozzle forms a mechanical seal to the male piece. What is happening seems to be that the pieces are getting fused together where they make contact with pressure created from torquing the capnut down. There is no problems with the threads... it seems more like it is some kind of binding of the material under pressure...
I do not know how to overcome this. Any suggestions? I cannot use antiseize as the owner does not like the idea because our customers will not use it in the field.
I do not know how to overcome this. Any suggestions? I cannot use antiseize as the owner does not like the idea because our customers will not use it in the field.





RE: stainless parts "locking up" - high temp/pressure... any ideas?
RE: stainless parts "locking up" - high temp/pressure... any ideas?
You can try heavily oxidizing the surfaces before assembling (high temp. treatment in air).
You could try spraying the parts with boron nitride spray prior to assembly.
You can just live with the fact that stuff made from 304ss assembled and subjected to 1750F is gonna stick to itself.
RE: stainless parts "locking up" - high temp/pressure... any ideas?
Aaron Tanzer
www.lehightesting.com
RE: stainless parts "locking up" - high temp/pressure... any ideas?
I will look into the boron nitride spray and oxidizing
RE: stainless parts "locking up" - high temp/pressure... any ideas?
Are you being hit with warranty claims because the parts are bonding?
"Wildfires are dangerous, hard to control, and economically catastrophic."
Ben Loosli
RE: stainless parts "locking up" - high temp/pressure... any ideas?
RE: stainless parts "locking up" - high temp/pressure... any ideas?
Pre-oxidizing the surfaces would help also. Heat first and then wash with BN.
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Plymouth Tube
RE: stainless parts "locking up" - high temp/pressure... any ideas?
I see you can buy cans of boron nitride spray on mcmaster.com can I just buy a can of spray and heat the parts and then spray the chemical on?
Thanks.
RE: stainless parts "locking up" - high temp/pressure... any ideas?
You might try 310 (nominal 25Cr 20Ni, actually available stuff is 310S UNS S31008)
It will still gall.
In Ancient Times General Electric's jet engine guys in Cincinnati used white Philips Milk of Magnesia as anti-seize. It is just magnesium hydroxide, entirely harmless to the alloy, and will not break down as will boron nitride at your 1750F temperatures.
However, the Boss or the Customer will laugh at this. To look more sophisticated, use a stop-off available from Wall Colmonoy. I disremember which is best but they have one for such applications. One just paints it on.
Also, regardless of alloy, you cannot maintain a clamping load at 1750F. The metal will relax and whatever clamping load you started with will disappear. Sorry, that's just the way it works.
RE: stainless parts "locking up" - high temp/pressure... any ideas?
RE: stainless parts "locking up" - high temp/pressure... any ideas?
USAeng, is the 1750 deg.F test applied only for a 3-hour test or is this the service temperature? Also, if this is only for a test, then why do you care if you can unfasten, as the coupling cannot be reused anyway?
Please clarify.
Aaron Tanzer
www.lehightesting.com
RE: stainless parts "locking up" - high temp/pressure... any ideas?
the actual temperature that the pieces will see may vary from 1200F - 1600F this is on a daily basis
I will keep trying to push the antiseize unless there is something like silver plating or other more permanent solution I should try... but I think silver plating may not be good for these temps...it melts at around 1750 so at least for our testing it would be no good
RE: stainless parts "locking up" - high temp/pressure... any ideas?
I believe that Saint Gobain has the BN business. the trade name might be Combat, but it has been years.
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Plymouth Tube
RE: stainless parts "locking up" - high temp/pressure... any ideas?
Aaron Tanzer
www.lehightesting.com
RE: stainless parts "locking up" - high temp/pressure... any ideas?
Stop-off is useful for blocking braze alloy migration, but it too becomes brittle when it dries, and I don't believe it will form a film and stay put in interfaces. Probably worth a test.
Better solution would be to move the nozzle joint to a lower temperature zone?
RE: stainless parts "locking up" - high temp/pressure... any ideas?
Mike Halloran
Pembroke Pines, FL, USA
RE: stainless parts "locking up" - high temp/pressure... any ideas?
I think the boss is coming to same conclusion that me and the rest of my coworkers came to - that is we are testing at too high of temperatures... I think the diffusion bonding may not be as much of a concern at the temps of 1300-1400F but we will see... I like the idea of the boron nitride spray so I will look into that today
thanks a lot
RE: stainless parts "locking up" - high temp/pressure... any ideas?