Hydraulic Pump Noise... but not always.

[oldnslo]

Rd
Pump cavitation is when the pump is drawing air on the suction side and when pump is attempting to build pressure this cavitation creates noise and destroys the pump.

power beyond is the term for an open center valve where flow exits the valve and can be used to power equipment down stream. On 99 percent of mobile valves you cannot pressurize the tank or return line

closed center valves do not require a power beyond.

from what I am reading in your posts you do not appear to know what type or size of pump was on this machine originally and or what style of valves you have.
my suggestion is to figure out what style system you have before you damage something

 

[RDSmith]

I certainly agree in that I need to figure out things before something is ruined. I only used a gear pump because a guy with a similar but newer unit uses a gear pump too. I guess it could be just a pressure relief vibration since I don't really know what cavitation sounds like but it just the fact at people have raised the possibility of cavitation scares me. I have a crude drawing of what it looks like to me. I just don't understand yet if it's a closed or open system.

 

[K5lwq]

What you have drawn would be closed center. With open center you would not tee into the power line before the first valve. You would have a third line coming out of the first valve feeding the second.

You do not have to worry anymore about cavitation. You problem is you are dead heading the pump ever time your valves are in the neutral position.

You will have to either change the pump to use your current valves or change the valves to be open center with power beyond for your current pump.

 

[RDSmith]

Thank you. Thank you. I think I get what you mean. If I could change things like in my new crude drawing with fluid flowing from control to control in series with appropriate changes it could be open? And the vibration and noise would go away. Or connect the hoses for the motor in the top left to one of the unused positions on one of the gang controls? Obviously I don't understand the advantages to how things are right now if I used another type pump.

 

[KWentling]

I agree that what is drawn is a closed center system. You don't find tees on the pressure side of an open center system. What is operating the hydraulic motor? Is there a valve not shown? If it's as drawn the pump would not be dead headed as there would be flow through the motor to the tank.

 

[K5lwq]

That drawing still would not work because your valve would not handle the back pressure when you use the second valve.

You would have to know what brand and model of valves you have. Both would have to be changed over from closed center to open center. This is possible on some valves but not all. It normally is Accomplished by a plug that is installed in the tank port. Then on the first valve you would need a power beyond sleeve as well.

I don't have time to draw it for you now but someone will. If not I will do it later.

 

[oldnslo]

RD,
Like Kwentling stated the hydraulic motor shown in your schematic is a big question mark. What is it driving or operating and are there any valves in the line to this motor. The motor might be what is providing a flow path for the oil to tank and creating the 1600 PSI you mentioned when none of the valves are operated.

I would not run the pump again until you determine if there is a relief valve in one of the valve stacks limiting pump pressure since if not and you block the flow the weakest link will break. Could be a hose, pump housing, drive coupling, etc. but something will break.

 

[RDSmith]

A lot for me to digest from you guys. Let me say this right now. When this mill was manufactured I'm guessing a gear pump was used and mounted somewhere on the "carriage" and driven by the Kubota engine that's there now. Remember I'm guessing a little here. Later someone changed things and used an electric motor to drive a pump that was away from the saw. I'm trying to go back to something more original seeing there isn't three phase here and I'm putting the saw away from buildings and electricity.

I know my drawings are messy. The valve by itself is one of those that isn't self centering and controls a motor that drives the carriage back and forth on a track. Fluid leaves motor and goes to tank. The log stays stationary and the band blade moves with the carriage. See drawing. Four other motors controlled by two levers/spools/valves. I just don't know the correct words. I also can't see identification on the valves. In 1999 and 2000 the company used Prince SV stack valves.

 

[KWentling]

There are pressure relief valves on the right hand end of both valve banks. Curious what the smaller hose on the relief valve is. Pilot operated relief
maybe? The grey valve in the top left of picture 3. Is that the valve that operates the carriage motor direction? Is it plumbed to one of the other valves to provide on/off? Still thinking this is closed center.

 

[oldnslo]

Was curious about the extra hose off the end of the relief valve. RD can you trace where the small hose on the right hand end in picture 2 goes?

Wonder if this was originally a double pump with a pump for each valve section? I know quit throwing out more things to consider...

Agree that everything seen so far would point towards a closed center variable volume pump system.