Hydraulic pump unloading valve
Hydraulic pump unloading valve
(OP)
new to hydraulics - I have a bank of 4 hydraulic pumps @ nominal 90 gpm each powering various hydraulic equipment (reactor agitators, etc.). The pumps each deliver to an unloading valve and then to system or reservoir. As the fluid is returned (from plant) it goes through a cooling heat exchanger and then back to reservior. Pumps are turned off/on depending on required load. When we only have one pump on and a low flow condition the unloading valve sends flow back to reservior and the cooling heat exchanger is by-passed - this results in a very high temperature increase if not discovered. Question, can I re-route discharge from the unloading valve from the reservior to system return line where it will cath the exchanger? Thanks.





RE: Hydraulic pump unloading valve
RE: Hydraulic pump unloading valve
RE: Hydraulic pump unloading valve
You should be able to run the 'relief' thru the cooling system but it's hard to say without actually seeing your schematic.
Is this a common situation with the excess needing to be dumped? HP?
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Hydraulic pump unloading valve
RE: Hydraulic pump unloading valve
You MIGHT be able to reroute, BUT it sounds like the heat exchanger you are thinking about going to is after the process equipment and pretty much at the end of the lines. If this is true, you might have lost considerable pressure before you reach the exchanger. If that is the case, it is possible that the heat exchanger has a design pressure much lower than the pump discharge and of course it would not be acceptable to reroute high pump discharge pressure into a lo pressure exchanger. Please find some engineer and have him CHECK THE RATINGS of the exchanger, its relief valve settings if any, piping and everything inbetween.
Perhaps better suggestion for present is, first, check the minimum flow requirements of the pumps. (API actually suggests min op flows not lower than 60% BEP to avoid long term damage.) It sounds like you are operating at very low flow rates. Probably much lower than intended. If not, maybe you are operating at low flows for much longer time than intended in the original design. Review your current operating practices and current flow rates versus the intent of the original design. It just may be a change in pumps or modification of the pump could be the best solution. Doesn't hurt to check that first.
http://virtualpipeline.spaces.msn.com
RE: Hydraulic pump unloading valve
RE: Hydraulic pump unloading valve
RE: Hydraulic pump unloading valve
There is no cardinal rule that PVB style pumps couldn't be unloaded but it is not necessary-if there is little fluid moved back to tank I would be concerned about the filtration and might put in a recirc unit(kidney loop) with both a filter and heat exchanger. Maytag
RE: Hydraulic pump unloading valve
RE: Hydraulic pump unloading valve
Pressure compensated controled pumps are common on large central systems but they are not the most energy efficient. But it only uses very little energy to provide makeup fluid if no work is being done(makeup for case drain and any fluid required thru out the system) but not to include fluid bypassing over a relief valve that is either faulty or set lower than the pump is trying to produce. An amp probe would shed lite on how much work is being done with the system at rest. Maytag
RE: Hydraulic pump unloading valve
RE: Hydraulic pump unloading valve
I always get to the Relief Valve and turn the adjusting device in to see if pressure increases. If it does it means the Compensator is set higher than the Relief Valve and all flow is going across the Relief Valve instead of the pump reducing flow to that required by the circuit (even to no flow).
Adjusting a new setup goes like this:
Raise the Relief pressure to maximum. If it is spec'd. correctly that will be at least 2-300 PSI higher than system desired pressure.
Raise the Compensator pressure 2-300 PSI higher than system desired pressure.
Reduce Relief valve pressure to 150-200 PSI higher than desired system pressure.
Reduce Compensator pressure to desired system pressure.
At this point the Relief Valve is set 150-200 PSI higher than the Compensator and the pump only has flow if the circuit requires it.
Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com
http://www.fluidpower1.us
RE: Hydraulic pump unloading valve