Hydraulic oil high temperature

[amar122amar]

We have a highdraulic oil operated valve. Hydraulic oil pump discharge pressure is 150 bar. Over a period of time oil overheats (to around 63 deg C) and high temp alarm is generated. If we take pump changeover then oil temperature comes down to normal (around 50 deg C). There is oil leakage (one drop per sec) in hydraulic Cylinder piston seal. Valve position controller output remains same but actual valve opening varies around 1%. Pump discharge pressure fluctuates by around 5 bars. There is fluctuation in motor amps by around 4 amps. We undrstand that high temp is due to oil leakage but why temp comes down by pump changeover?

 

[itsmoked]

What exactly do you mean by "pump changeover"?

Are you mechanically changing out the pump or switching to an second installed pump?

If it is a second installed pump, is it drawing from a different location in the reservoir?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[boo1]

Leakage does not creat heat. Hydraulic system's heat load is equal to the total power lost (PL):

PLtotal = PLpump + PLvalves + PLplumbing + PLactuators

When the PLtotal is greater then the Q dissipated, the system will overheat. Consider a hydraulic heat exchanger.

 

[amar122amar]

Pump change over means starting the standby pump. Both pumps take station from the same side of hydraulic tank.

 

[maytag]

amar,

The more info you provide the better answers you will receive, i.e., schmatic, type/model of pump etc.
Hydraulic power that is not used for work is converted to HEAT and there are plenty of systems with the inefficiencies designed out and run within an acceptable viscosity range without a heat exchanger.
Just a WAG from the info you provided is that you have an axial piston pump that is worn and leaking internally
(if this is the case check the case drain flow).

Maytag

 

[hydromech]

I agree with maytag...

That is assuming that the pump has a casing drain. If it does have a casing drain, check the temperature of the pipe when the pump is running at high pressure. If the temperature of the standby pump is lower than the other pump, it will prove that the pump is worn.

Internal leakage does create heat. Pressure lost through worn valves/pistons is converted directly to heat.

I can tell you that your leakage is not large because the temperature rise is not large and not quick. Having said that you temperature margins are small. As the system wears the heat generation will rise and if you reservoir cannot disipate the heat, the tank will get hotter and hotter until the temperature differntial between the tank and the ambient air is high enough that the heat can be dissipated.

Why set the over temp alarm to 63 degrees?

Hydromech

 

[hydtools]

Does the "pump changeover" simply circulate the oil? Heat generated may be less than that of the original pump and system and less than the capacity of the system to give up heat, therefore the "pump changeover" runs cooler. The second pump may leak less than the first pump and therefore generates less heat and the system can reject enough heat to remain cooler.

Agree with Maytag, need more information. We are just guessing, now.

Ted

 

[Ron]

Standby pump and piping are probably "cold" compared to operating pump and piping. Temperature drop is not much so this could account.

Check the viscosity vs. temperature of the hydraulic oil. The seals can handle certain viscosities and temperatures, so set alarms accordingly if not already set that way.

You might want to consider alternating the pumps and cycle based on temperature.