Hydraulic problems on QT 20

Hi everybody.

I'm having a problem with over pressure on my hydraulic main. I'm suspecting the pump, but not leaving out a possible motor problem.

My main pressure is at 1100 psi, and the whole hydraulic system is running really hot. I stuck a thermometer in the tank and the hydraulic oil is hitting 120 degrees F. We recently had mazak in to repair a leak. They cleaned out the drive area and the hydralic pump tank. When we took the tank apart, we noticed the coupling between the motor and the pump had disentigrated and the keyway was gone. We replaced the coupling and the keyway. All the hoses were changed. When we fired it up, we had the overpressure and the heat. This was happening before as well. Any Idea's?????

Hey vantim,
1100 psi main system pressure is way too high! There should be a green mark on the main system guage for the normal set pressure. Around 450-500 psi, I think.
You can adjust the pressure at the pump. Of course, it's a bitch to get to the pump if it is the submerged type. It's kind of a trial-and-error method: pull the pump, adjust the pressure screw, reinstall the pump, test for main system pressure.
Most pumps have 2 adjustment screws: one, for main pressure, and one for flow rate. Make sure you know which screw you need to adjust.
Of course, if your motor to pump coupling went bad, your pump may be on the brink. Maybe a high pressure condition is sign of soon dying??
Give the pump maker a call. Probably Parker Hannifin. They should be able to help.
Good luck,
Greg

You might change the gage. It might read 1100psi but I have had them go bad and read high before.

Vantim,

If you have a Parker pump, it may well be a variable displacement piston pump. Parker has a catalogue on these pumps at:
www.parker.com/pumpmotor/cat/english/1553a002.pdf

Both cnctoolcat and Integrexman suggestions applied to my recent experience on a QT15. When I opened up the gage, I was amazed to see how the pulsing [probably the initial start-up of the piston pump] had hammered the linkage connections in the gage.

Good luck.

Outback

Thanks for the info toolcat. I didn't realize there was a adjusting screw on the pump. I'll check into that and let everyone know. Sorry, I've been gone for awhile.

outback... it's a parker pump. Thanks for the link to the catalogue. I had already checked it out. Luckily parker hannifin is only 5 minutes down the road from the shop. I'll get to the bottom of this yet.

The gauge is fine.

did you take the pump apart?
you may have it assmbled wrong
if so no amount of ajusting will bring pressure down