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Dielectric pump issue, Cavitation?

claya

Cast Iron
Joined
Aug 6, 2006
Location
california
Sinker EDM, but the following applies to any pump based fluid system.

If the dielectric is foaming a lot, or there are bubbles in the outlet what does that indicate? I can hear the pump cycling (cavitating??). The fluid is basically brand new. The cavitation is about every 5 minutes...

Actual pump pressure is OK (15-18 psi) at startup, but then it slowly drops to basically 1psi. When it starts cavitating, the pump pressure rises to ~10psi during the cavitation, then drops again.
Is the pump losing prime, then recovering like a vac leak? Or is the pump pickup getting restricted? There is a simple filter on the pickup. The dielectric is new, but it does not look like what I would call clean in the sinker tank when filled.

Filter pressure is steady at 5psi, then rises to 12psi when the pump cavitates. Pump sounds like ball bearings. 20gal in the tank.

According to the book, the pump pressure should be 35-40psi. I have never seen it that high. The machine is 1986 era. Maybe the pump is super worn? Or there is a shaft seal that is bad?
 
Have you tried bleeding the air from the dielectric filter housing? I've got an old Elox, and used to run Easco Sparcatrons. After replacing the filter(s), you turn on the pump and open the petcock on the housing until only dielectric comes out. You have to be quick, or you'll get a shower! (ask me how I know!)You'll want to repeat this a few times to make sure the air is all out. Hope this helps! ------------------ John :cheers:
 
Bled the filter. No diff. If I prime the pump, it only stays at pressure (15-18psi) for about 6 seconds. Then drops to ~1psi.

I must have a air/vac leak. Or a pickup problem?

Sent from my SM-G975U using Tapatalk
 
Bled the filter. No diff. If I prime the pump, it only stays at pressure (15-18psi) for about 6 seconds. Then drops to ~1psi.

I must have a air/vac leak. Or a pickup problem?

Sent from my SM-G975U using Tapatalk

There are several things that can cause cavitation like issues.

First is your tank actually full. The pump might be just sucking air from a low level.

Since you mention that your pump pressure is low, is the supply valve wide open? On many systems, the supply valve is used to throttle the pump flow. If you are overflowing the system design flow, you can end up with too much coolant in the machine and very little in the tank causing what you are experiencing.

I would adjust the pump pressure to the stated pressure and see what happens. Bet the problem goes away.
 
I bought a machine years back that had pump issues. I took the pump out to find years of crud and what I believe to be pcs of scotch Brite pads stuck in it. Once I cleaned it, ran perfect.

Might just need a good cleaning.
 








 
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