Where To Measure For Max Hyd Press.?

[jimainiac]

If you want to find out what the maximum pressure is in the tractor's hydraulic system, can you hook up a gauge anywhere in the system? Will it measure the same no matter where you attach the gauge? Thanks for any thoughts...

 

[kennyd]

Jim, you need to deadhead the pump to check the pressure that the PRV is set for. The easiest way to do that is to plug a gauge into one of your loader ports or a rear remote if you have one.

If you do not have a FEL or remote than you will have to find the test port on your machine.

 

[jimainiac]

kennyd- Thanks for the response. I was hoping it was okay to put the gauge in the rear remote.
Sorry to be stupid, but what does "deadhead the pump" mean? Does that mean to actuate the remote valve to ask for maximum pressure?

 

[kennyd]

Yes Jim, plug the gauge into on of the couplers for your rear remote, then move the lever to energize that port. The system will go into "relief" and the pressure will be indicated on the gauge.

 

[SPYDERLK]

kennyd- Thanks for the response. I was hoping it was okay to put the gauge in the rear remote.
Sorry to be stupid, but what does "deadhead the pump" mean? Does that mean to actuate the remote valve to ask for maximum pressure?

Deadhead the pump means to stop its flow. Strictly speaking this situation will destroy it or something else in the hyd circuit in a heartbeat. What he means is to valve the fluid to a port that will not allow flow - essentially a dead port. If your tractor is set up right, there will be a relief somewhere in the pump pressure output line [located before or in the valve] that limits the pressure rise safely to the relief pressure. You check P on the dead port [the remote with a gauge plugged in], adjust that relief, and recheck. The pump itself is not deadheaded.
larry

 

[john_bud]

If you want to find out what the maximum pressure is in the tractor's hydraulic system, can you hook up a gauge anywhere in the system? Will it measure the same no matter where you attach the gauge? Thanks for any thoughts...

You can check the pressure anywhere in the systems AFTER the relief valve. Let's get that straight. The flow is PUMP --> RELIEF VALVE --> GAUGE

You can put the gauge on the output from the loader control valve and use the lever to actuate it. That's a generally convenient location. Or the rear remotes. The pressure will be about the same anywhere in the system as long as you give it time to equilibrate. On the loader port, give it a solid 5 seconds after the relief valve opens. You do want to have it in a location where you control flow to the gauge with a valve.

One last point. You need (NEED) to check the pressure after the fluid is at full operating temperature. Cold fluid can't flow across the relief port at the same speed as hot fluid and you will get a false high reading. Also, any internal leaks in the spool or pump will be reduced by the thicker fluid. Normal temp is 140-160F

 

[jimainiac]

Thanks everyone for the replies, it's making sense now. I did put the gauge in a rear remote port. John Bud, that was good to mention warming the fluid to operating temperature - the service manual indicated that, also, so I moved some snow around for a while to warm it up good. Another thing the manual said is to run the engine at maximum speed, so I ran it at 2600 RPM, which is about PTO speed.
One more question - when I actuated the remote valve, the pressure would momentarily spike to 2500 lbs. and then fall back 2 or 3 hundred lbs. I wonder what I should be going by, the spike, or the more constant pressure. The manual says that the factory spec. is 2480 to 2625 psi., so I think I can safely increase it a bit. But how much I bump it up depends on what reading of the gauge I go by.
All thoughts welcome...

 

[john_bud]

2500 is the pressure the system hits while the pump continues to build pressure and before the relief valve opens. That is a transient condition. The lower and relatively steady pressure of 2200 to 2300 is the system pressure. I would bump that up to a steady state of 2700 psi. It will drop back some over time.

You will also want to check it again in July or August. Even with some work, it's about impossible to get to full temperature in winter.

jb

 

[3RRL]

My question is does your pump have it's own relief valve separate from the working valves such as your fel or rear remote valve? Otherwise you are setting the pressure relief for the valve you are working.

For example, my Chinese tractor does not have it's own pressure relief valve built in. I could dead head the pump and destroy it if it wasn't connected to some other valve which has a PRV on it. So I installed a relief valve right after the pump on the high pressure line out of it. I then installed a gauge coming out of that relief valve. The gauge is plumbed into my system now. My manual tells me the maximum pressure for the pump so I set THAT relief valve to right at the maximum pressure. Now I know my pump will make maximum psi but not more that what the main PRV is set for.



Then I used the same gauge to set all the other valves in the system by operating that valve and setting it's own pressure relief. I set the other valves at 50psi below the Main pressure relief valve for safety reasons. In fact, I don't even need to do that now since the system has a Main pressure relief valve which would relieve if the pressure started to build up over it. But I set the other valves slightly lower to avoid any possible problems in case the Main relief valve ever fails, OR in case my wife forgets to reconnect the hydraulic lines if they have been disconnected.