Rotating Connection to 700 Deg F Pipe 1

[triage]

I have a fixed 1 1/8" O.D. pipe which ranges in temp from ambient to a peak of 700 Deg F.

I need to attach a component to the pipe which must be thermally isolated from the pipe and can freely rotate about the pipe, like a wheel about an axle.

Is there a high temp, thermally non conduction bushing or bearing which can be used. Price is an issue and cheap and simple is the primary concern.

The rotation is not precise, just needs to be free to rotate.

Any ideas are welcome. I found a ceramic bushing, but was blown away by the price. Also not sure that ceramic would handle the expansion and contraction of the pipe from ambient to 700.

 

[Compositepro]

The questions I have would be much longer than your post so I gave up. Your problem does not soud difficult so I'm sure there are other constraints you haven't mentioned.

 

[unclesyd]

Like Compositepro states there many questions that need to be asked about your problem.

A very short list:

Can you stand any heat transfer?

Load and RPM of the thingy?

 

[chief]

Check out Chiksan connections as used in the oil drilling industry. Pressures up to 10k psi, Not sure about temperature limit as it would depend on the type of seal fitted.

Offshore Engineering&Design

 

[triage]

Compositepro,

There are no other constraints and it should not be difficult.

Chief,
Pressure has nothing to do with this problem. The pressure within the pipe is irrelevant.

Component is attached about the pipe and is balanced like a wheel about an axle. Pipe is copper.

The pipe is very hot and I want to make a fixed connection to it which will allow for rotation about the pipe, without transferring heat from the pipe past the connection point. If there is a simple solution, I am all eyes.

Radial Load is < 50 lbs and max rpm is 10 rev / min. The pipe is horizontal to the ground, so there is no lateral or thrust force on the connection.

 

[unclesyd]

Here are two approaches that may have potential in your case. I would checkout the dryer bearings from Metalized Carbon to see how much heat is transferred across the bearing. The second approach is to use a Mica bushing either alone or as a spacer between something like the dryer bearing and the rotating device.

http://www.dryerbearings.com/index.html

http://micasales.com/#mica_products

Another way might be to use ceramic or carbon foam as a bushing.

http://www.ultramet.com/refractoryopencells.html

http://www.ergaerospace.com/index.htm

http://www.blaschceramics.com/products/product.cfm?ID=4&prodID=56

Even another way might be is to use a packing gland and use Graphite, glass, or ceramic packing. Your project would be a no brainer if one could still use Asbestos.

http://www.garlock.com/ViewProduct?region=1&product=15

http://www.minseal.com/

Yet another way would be to use a packing gland arrangement and use something like LPS to mold a bushing over thing metal sleeve.

http://www.unifrax.com/web/UnifraxH...942005562f2?OpenDocument&Highlight=0,moldable

 

[triage]

Thanks Unclesyd,

The dryer bearings look like just the thing, but will also consider lathe turning our own bushings from a high temp bonding cement as avail at unifrax.com

In our initial plan, we just assumed there would be very inexpensive high temp bushings made from ceramic, widely available. I have not found this to be the case.

Regards,
Triage

 

[unclesyd]

Your mention of machining jarred a sleeping neuron and here is another approach using machinable ceramic. Watch out as some are good thermal conductors.

http://www.crystexcomposites.com/new/index.ph

http://www.aremco.com/a1.html

 

[MJCronin]

triage....

Copper is not a suitable material for this 700F application, as per the rules of ASME B31.1.

I suggest one of the stainless steels...

-MJC

 

[triage]

MJCronin,
Thanks for the advice, this is not a power application and hence is not subject to ASME B31.1, but I agree that copper pipe is not applicable for this application if it were operating under pressure. It's just hot, and well below its melting point.

BTW, found an afordable graphite bushing for the job, thanks for all of the contributions.