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... I have a question as I begin to put together my setup. I’ve read that with some pumps it is important to run the pump for a bit with valves shut to evacuate the system before turning off. Is this correct? Does anyone know if it is necessary with the Thomas 2660 pump? Do folks do this? Any other regular pump maintenance to be aware of? Thanks!
I don't know anything about the Thomas 2660 vacuum pump specs, but Gast rotary vane vacuum pumps do have a shutdown procedure in the Operation and Maintenance manual. The procedure is to first run the pump open port for five minutes (open port means all plumbing completely disconnected from the pump). Next, the pump is run blocked port for ten minutes (blocked port means the vacuum port is closed with a plug or valve). And, finally run the pump for five minutes open port.
If you don't receive a manual with your vacuum pump I'm sure that it can be found on the Thomas website. I believe that the purpose of the shutdown procedure is to clear any residual moisture from the pump and to cool the pump down.
I loosely follow the shutdown procedure sometimes, but not always. I have a 1/4" NPT brass T installed on the vacuum port of my Gast pump with ball valves on the other two legs of the T so that I can easily do the shutdown procedure without disconnecting the plumbing from the pump. I would guess based on past discussions that most woodturner owners of Gast rotary vane vacuum pumps have never heard of the shutdown procedure and wouldn't follow it anyway.
What I learned is to open the bypass all the way to take the load off the pump before turning it off. The backlash from leaving the vacuum high may damage the pump.
This isn't an issue with rotary vane pumps because the vacuum disappears as soon as the pump is turned off. This is because there are no valves unlike piston or diaphragm pumps. When a rotary vane pump stops the vanes no longer are extended by centrifugal force and therefore the vacuum side is open to the ambient air pressure.
Even with piston and diaphragm pumps the vacuum will quickly disappear because of system leaks ... mostly around and through the wood, but also leaks from the bleed valve and rotary coupler.