Guys, Im trying to increase the pressure on my log splitter. I have a pto driven pump (not sure what it is, its old) that is plumbed to a Gresen model 400 control valve. After searching online I found a manual for this model. It describes how to add shims to the relief valve to increase the pressure. I followed the instructions but it had no effect. After scouring the internet some more I ran across a blog that explained this same problem. It explained that the system needed more volume. In other words a bigger pump. My question to you hydraulic guys is does this sound like the problem. I would like to get some additional feedback from the guys I trust. Thanks in advance
log splitter relief valve shims to increase pressure
- Thread starter Hiltz
- Start date
schmism
Super Member
have you put a gauge on the system?
if the pump puts out 2500psi and thats what the gauge says, there is no shim fix for that problem.
flow rate of the pump (volume) = speed of the ram.
pressure (psi) = how hard the ram can push.
generally speaking a larger volume pump is not always higher pressure. in fact its much easyer to get high pressures with low volumes than it is to get high pressures at large flowrates.
flow rate = hp requirement. generally the more flow rate the larger the HP requirement. (for a given HP, its easyer to drop the flow rate and increase the pressure than it is to increase the flowrate AND pressure)
SO ultimately what are you after? more speed (quicker cycle time) or higher splitting force?
if the pump puts out 2500psi and thats what the gauge says, there is no shim fix for that problem.
flow rate of the pump (volume) = speed of the ram.
pressure (psi) = how hard the ram can push.
generally speaking a larger volume pump is not always higher pressure. in fact its much easyer to get high pressures with low volumes than it is to get high pressures at large flowrates.
flow rate = hp requirement. generally the more flow rate the larger the HP requirement. (for a given HP, its easyer to drop the flow rate and increase the pressure than it is to increase the flowrate AND pressure)
SO ultimately what are you after? more speed (quicker cycle time) or higher splitting force?
I put a gauge on the system and all I can get is 1300 psi. Thats before and after the shims. Im trying to get more ram force
jenkinsph
Super Star Member
Is the relief opening up and dumping the oil back to the tank? If not the pump may be the culprit.
Has the pump been tested to verify it can still produce the original flow and pressure ratings? It may be worn enough it can't pump at higher than the 1300 psi.
Ideally a two section pump with a wider high flow gear set and a second narrow gear set capable of higher pressures would be the best scenario.
J_J
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Resistance to the hyd fluid determines the pressure. GPM's determine the speed of operation.
You need to determine if the pump is capable of operating at designed pressure.
You need to verify that the relief is working correctly.
The valve might be leaking.
You need a good cyl and valve to determine the cyl's capability.
You should get more than 1300 psi with the cyl fully extended. Usually about 2500 to 3000 psi.
If the cyl seals are leaking, it may be difficult to obtain good test pressures.
If you have the relief valve cranked to max, and the valve is good, then the cyl seals are bad.
You need to determine if the pump is capable of operating at designed pressure.
You need to verify that the relief is working correctly.
The valve might be leaking.
You need a good cyl and valve to determine the cyl's capability.
You should get more than 1300 psi with the cyl fully extended. Usually about 2500 to 3000 psi.
If the cyl seals are leaking, it may be difficult to obtain good test pressures.
If you have the relief valve cranked to max, and the valve is good, then the cyl seals are bad.