Pump problems

will smith_4

Puzzling pump problemWe installed a Mepco vacuum/transfer tank

system a while back, and this season so far we've lost 4 pumps-in each

instance the shaft sheared, leaving the impellers just laying in the

volute. The last one didn't last two weeks. Manufacturer's rep initially

felt it was due to steam coming back to the tank-but we don't have live

steam coming back. The next thought was that it was due to a spacer

between the lock down bolt and the impeller, and this was supposed to

have been changed-but the last one I pulled out which was supposedly a

different design still had the suspect spacer.

Anybody seen anything like this? Certainly a first for me.

Thanks in advance-

Steve Whitbeck

pump

If this is a wet rotor high RPM pump and the shaft is sheering off - That is usually caused by air bubbles in the water stream. The air allows the impellar to free rev and than when it pulls in solid water the impellar instantly slows and sheers the motor shaft.

will smith_4

Air bubbles

Steve-

Is there any possibility that a defect in the design of the vacuum tank could be allowing air bubbles to cause this? I gotta think you know your pumps just from what you've put forth here now, and since we're multiple thousands of dollars into this with absolutely no clear cut answers, I'll be totally honest when I say I'm ready to look at this problem from all possible angles. The manufacturers and the reps want to look a different direction-I get it. All I want is to solve the problem.

Thanks for your interest so far, and for what ever other direction you can point me in

Will

icesailor

Vacuum Pump Problems:

I'm sure that this pump is used in this application regularly. It may not have problems in other applications. You are having problems in yours. So, I ask, what's different about yours?

Remember, in a pump, the higher the vacuum, the lower the boiling point. If you have anything that causes restriction, the vacuum will go up.

There shouldn't be any air bubbles in the water coming to the pump. But the impeller will create lots of air through cavitation. What kind of vacuum do you have going to the pump? Could it be going up momentarily when you aren't around?

I made a "rig" to check to see if water heater expansion was causing relief valves to blow off. To make one for vacuum, take a 1/2" IPS brass check valve with a rubber poppit/seal. Bush a vacuum gauge in the end so it will register vacuum. Put it in and leave it. It will show if you are getting vacuum spikes.

What do the ends of the impellers look like? Can you compare a broken one with an unused one? That do the compare like? It doesn't take much wear to make them not work well. The slightest wear on the ends of the vanes can show that something is going on.