oildyne hydraulic pumps..

[Chuck Wintle]

we have this pump at work and it can no longer maintain its nominal pressure. Often times when we start the pump it will stay steady at 600psi and after a bit the pressure will vary up and down from 400 to about 600 psi. Lately when we start it it will stay below its nominal pressure of 600 psi. no amount of adjusting of the adjustment will bring it to 600. It now wants to stay around 550psi. What is in these pumps that can fail and cause this problem....

Thanks in advance to all.

HYGE_Oildyne_550.jpg

[Jerry Bruette]

Obvious stuff first...Oil level o.k. in reservoir?

Could be a leaky pressure relief valve.
Solenoid valve could be leaking.
Whatever your powering, cylinder etc., could be bypassing and not holding pressure.
Possibly a dirty filter.

Don't know where your taking the pressure reading but that would help troubleshoot the system. Pressure reading at cylinder or on the pump itself?

[Chuck Wintle]

Obvious stuff first...Oil level o.k. in reservoir?

Could be a leaky pressure relief valve.
Solenoid valve could be leaking.
Whatever your powering, cylinder etc., could be bypassing and not holding pressure.
Possibly a dirty filter.

Don't know where your taking the pressure reading but that would help troubleshoot the system. Pressure reading at cylinder or on the pump itself?

We think its a leaky pressure relief valve. The filter is brand new, and there is not a solenoid valve.

[Tom Stenzel]

Not familiar with the Oildyne line so I have only the usual generic info.

The pump you show is rated for 3000 psi. 600 should be no problem unless the pump is seriously worn out.

The fluctuating oil pressure sounds like air in the system, or the pump is sucking in air. It *looks* (means I'm guessing here) like the pump is submerged in the oil tank precluding an air leak in the pump suction line. Could that power unit have been reassembled or installed so that the pump is no longer in its proper orientation? That is, the suction side of the pump is pointing up or is higher than the fluid level. If there's a This Side UP arrow on it somewhere they mean it.

The rated max temp for the 550 is 140 degrees F. At that rating it will have nitrile rubber seals inside. If it was allowed to seriously overheat to over 200 degrees the seals inside would melt. If something like that happened all bets are off of it working. Could that have happened somewhere in the past?

Jerry might have nailed it with the load (cylinder or motor) having an internal leak and allowing fluid through. Make sure the problem is with the pump. I've seen leaking piston seals act pretty erratic and deflected the blame elsewhere.

Hope you pin it down quick.

-Tom

[Chuck Wintle]

Not familiar with the Oildyne line so I have only the usual generic info.

The pump you show is rated for 3000 psi. 600 should be no problem unless the pump is seriously worn out.

The fluctuating oil pressure sounds like air in the system, or the pump is sucking in air. It *looks* (means I'm guessing here) like the pump is submerged in the oil tank precluding an air leak in the pump suction line. Could that power unit have been reassembled or installed so that the pump is no longer in its proper orientation? That is, the suction side of the pump is pointing up or is higher than the fluid level. If there's a This Side UP arrow on it somewhere they mean it.

The rated max temp for the 550 is 140 degrees F. At that rating it will have nitrile rubber seals inside. If it was allowed to seriously overheat to over 200 degrees the seals inside would melt. If something like that happened all bets are off of it working. Could that have happened somewhere in the past?

Jerry might have nailed it with the load (cylinder or motor) having an internal leak and allowing fluid through. Make sure the problem is with the pump. I've seen leaking piston seals act pretty erratic and deflected the blame elsewhere.

Hope you pin it down quick.

-Tom

To solve the pressure problem we ordered a new motor/pump unit. There seems to be no repair kit available to refurbish the pump section so there was no choice to buy a new one. This pump is only 4 years old, only pumps 'clean and polished" oil and is gravity fed.