Dry Running Circulators

Stokehold

In checking a system with compressed air prior to filling with water, I notice that the circulators will spin. Will dry running for this short duration cause any problems for these water lubricated pumps? Should the air be released slowly or can a valve be opened full. It seems to me that if you let the air out too quick, the pumps will spin very quickly.
Also, if a similar system is flushed will domestic water at 60 lb.PSI, will this cause any problems spinning a low volume pump?

Zman

I do not believe you will damage the circulators with the proceedure you describe.

hot_rod

Seems like the pump would only spin if you are flowing across it?

If you are doing a static air test how is the pump spinning unless there is a sizable leak of air downstream?

if the system is all piped you should be able to isolate pumps with valves and still pressurize the entire system from one point, like the boiler or expansion connection?

I believe fluid needs to be in the pump cartridge to lubricate the bushings.

Cavitation caused vapor pockets in a pump will cause bearing or bushing damage rather quickly.

Dave H_2

No, with the two situations you are describing.
1. Short amount of time and
2. they are not powered and running, just the air flow in the system is turning the impeller.

When we manufacture a circ and test before painting, they are all test run dry for at least 90 seconds with no affects. The speed of your circs with air flowing across is not the same speed as when they are powered (3450rpm).

Enjoy