Bolt Lube Rcommendation 5

[NX687]

Have an 18 bolt flange heated to 200 C

Taken apart often

would silver plated 5/16 UNF be better

than Grade 12.9 Cap screws with hi temp lube ???? Thanks

 

[desertfox]

What's the flange material,flange dimensions,external loads,enviroment,gasket material?
Please read your post and tell us from the information you've given how would you answer it, assuming you know nothing about this flange.

 

[dhengr]

If you’ve been watchin the ads these days, there are some fantastic new lubs on the market, for both the male and the female parts. Using them will have the nuts, bolts and flanges giggling and smiling during the entire screwing and unscrewing process. You actually have to watch out for premature torqueing during the erection process. Otherwise, Desertfox hit the nail (?) right on the head.

 

[Duwe6]

200°C is moderate, not high temp. Felpro C5A is pretty standard; copper & graphite, good to about 400°C.

 

[EdStainless]

In a joint that sees temperature cycling and frequent disassembly it very important to have the best thread quality possible.
Rolled threads, tight tolerances, and the right materials.
I would plate the the hardware, and also require the use of a lube.
In addition to silver there is MoS, WS, and a host of other very effective surface treatments.
The problem with using a lube is that it is hard to get people to clean it every time, and hard to keep them from using too much.
You also can no longer use torque as a criteria, you will have to use tension or elongation.
You also need to think about how to set a useful life for the hardware.


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Plymouth Tube

 

[tbuelna]

The key phrase in the OP is "taken apart often".

Silver plate is an excellent high temp coating for anti-seize on threaded fasteners. But after 1 or 2 installation/removal cycles the silver plating will be abraded off of the thread flanks. Unless you intend to replace the fastener with the silver plating (usually the nut) on a regular basis, then you'd be better off using some type of anti-seize lubricant compound that can be applied to the threads at each installation.

 

[EdStainless]

We used nuts on bolts that both had rolled threads.
We allowed nut reuse indefinitely (until the outside was damaged).
But bolts could only be used once.
Our bolts (actually studs) were all ground to a precision length and we used total elongation as a joint tightness criteria.
The mechanics hated it, but when we explained a few of the alternatives to them they got on board quickly.

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Plymouth Tube

 

[tbuelna]

EdStainless, you make a good point about checking for galling damage on the threads of studs/bolts made from materials that have a tendency to gall, like stainless steel or titanium, at every installation cycle.

There was a recent incident involving titanium studs used to attach the oil filter housing of the S-92 helicopter main rotor transmission. These titanium stud threads were subject to regular removal/installation of the mating locknut when the oil filter was serviced. Over time the titanium stud threads accumulated enough galling damage to cause some of them to fail. The failure of these titanium studs attaching the oil filter housing resulted in an S-92 transmission losing its lube oil, and eventually experiencing a catastrophic in-flight transmission failure.

Problems like this can be easily prevented by taking a few minutes to check the condition of fasteners before re-using them. Or for critical applications, by simply replacing the fasteners at each installation. The cost of replacing standard fasteners at every installation is always far less than the cost of a failure caused by a worn fastener.