PTFE Seal Temperature
PTFE Seal Temperature
(OP)
I have a PTFE (graphite filled) seal that I am testing running on a 2" shaft @ 500 RPM, 500 Psi. Test fluid is water at 50°C. It is grease lubricated. We are measuring temperature near the seal of 150°C which seems ridiculously high to me. Are you surprised by the temperature? I would never have guessed that a PTFE seal could generate that much temperature on its own. At this temperature you can't expect PTFE to perform a sealing application for long.
Any comments?
Any comments?





RE: PTFE Seal Temperature
I would not expect so high a temperature. To reduce temperature I would back of the preload at the gland nut a little, until I had a very slight leak, like a drip every minute or so.
If the seal is to tight, it will generate heat and the shaft will expand, causing more heat and more consequential expansion etc etc until it dissappears up it's own rear end in a puff of smoke.
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RE: PTFE Seal Temperature
RE: PTFE Seal Temperature
You give no details at all about your design, so I am taking SWAGs (Scientific Wild A** Guess)at it.
Any good design with PTFE will have some back up solid mechanical device to restrain or compensate for creep if the load is moderate or higher and is continuous.
All PTFE/graphite powder gland seal ropes I have seen are retained by an adjustable gland nut. This is for a very good reason.
Some have aramid fibre or carbon fibre reinforcement incorporated into the rope to reduce creep.
I cannot imagine a PTFE lip type moulded seal generating anything like that temperature, especially close to water at 50 deg C. To do this it would need to be so tight it would tear itself to bits in a matter of seconds.
Lip type seals are usually reinforced by a spring to preload the lip to the shaft.
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