Hydraulic Oil Temp

A total guess would be that pump 2 has a faulty motor or bad bearings and the heat generated is being transferred into the hydraulic oil.

I like the idea of air entrapment - but knowing next to nothing about hydraulics would there also be some other noticeable effect the air had in the 'power' strokes - eg, spongy....and is oil normally in need of cooling in a heat exchanger device - that needs cleaning?

Assuming that these are positive displacement pumps, usually such a temperature rise in the fluid indicates that most of the pump's flow is going through the pressure relief valve. This would indicate a restriction or blockage somewhere in the hydraulic circuit as PWSlack pointed out. Is a valve closed somewhere that should be opened for "pump #2?

One thing is not clear in your post. Is the problem happening when both pumps are operating, or when pump #2 is operating alone?

Yes, it's happening when only pump 2 in service.

Does pump #2 produce the same flow and pressure as pump #1?

Does one feel hot and one cool?

You aren't providing enough. ??? 20 questons?

What about post the hydraulic diagram?

Right now i am installing a system with such arrangement, and, sometimes , dirt gets into check valves, or pressure relief valves wrongly adjusted, leading to heatup. At the end, most of faults in my case come from unwanted pipe restrictions, or excessive flow set at the pump.

Personally, i check temperature of pipes after elements, better at the cold start.

Before i did with thermo-gun, now thermal camera for mobile phone (Flir One). Best 300 dollars investment in my life!!.

Salu2

Abel

Main causes of high oil temp are #1 restricted intake filter causing cavitation depending on severity you may hear the increased noise one method of confirming this is with an ultra sound detector, you may hear the bubbles bursting. #2 If these pumps have separate oil coolers then one may be defective using a heat gun inlet and outlet will show the temperature variation. Back the the ultra sound you should listen to both pumps and record the sound for trending. These devices Ultra Sound detectors are wonderful tools to spot problems way ahead of vibration and thermal sensors.

All hydraulic systems will generate heat via friction that is one method of heating the oil before production. How this is handled outside of normal range is the thermostat device used on coolant outlet of heat exchanger so it must be checked.

This is a good start let us know.

Get a sample of the fluid and have analyzed for wear metals. If you have metal contamination, you already know which pump it is.

Most likely internal leakage in pump #2 or in directional control valves unique to pump #2. Any high pressure delta P leakage goes straight to friction heating.

Usually hydraulic system pumps are positive displacement and control pressure with a relief valve. Usually mounted at pump so each pump has its own relief. The one heating the oil is probably leaking through (a leaking relief will cause oil to heat up). It may just have a particle of dirt under seat. Clean or replace.

If the same relief valve serves both pumps, then the heating when #2 is started indicates internal leakage in #2.

You have not referred anything about the flow quantity variation if any while pump No. 2 is started.

If the flow is less in Pump No. 2 and power drawn is the same as that of No.1 Pump Motor, than the flow of Pump No.1, the hyd.oil will get heated. This is due to to CHURNING EFFECT oil takes place on account of some clearances for the impeller are very high.

The oil pressure at the tip of the impeller will be very high than the pressure at the inlet of the impeller which is governed by the equation

((V1)^2 – (V2)^2)) / (2 x g)

where V1 is the velocity at the tip of the impeller and V2 is the velocity at the inlet edge of the impeller, and g is the acceleration due to gravity.

Pl. post the information about this flow.

DHAYANANDHAN.S

Agree, but would think that this is a PD pump on a hydraulic unit.