I picked up a used splitter with a bad motor, I put an 11hp honda on it with the existing pump, looks like a haldex 2 stage. Motor max r's is 3600 pump is good for 3600. the piston looks to be about an 3" with a 1-1/2 bore guages on the supply side of the piston and return side. I am new to hydraulics but no a little about mechanics. gauge on the foward motion maxes out at 500lbs but the return side will max out around 1500lbs. Is this somehow bypassing at 500lbs and is there any settings on the pump or controls that I can adjust?

Thanks

Is there some way you can plug your gauge directly into the working ports that go to your cylinder? Try each one with the gauge acting as a plug, and see if you get the same pressures. If you do, your problem is with the valve. If the pressure goes up to 2000-2750 psi, then it could be the cylinder.

The gauges are in the inlet and outlet of the cylinder, there is a nipple then a tee, the hose end goes in the branch and the gauge is in the othe r end on the run. Max pressure under load is 500lbs according to the gauge. Then on retract it gets to be 1000 to 1500lbs.

You shouldn't get 1500 psi just from retracting the cylinder. You shouldn't get 500 psi from extending it with no load, for that matter.

If your relief valve was set at 500 psi, then you would only see 500 psi on both the extension and retraction strokes. Your problem sounds odd, but my guess is that it's your control valve.

Posted 03 September 2008 08:23 PM
"Is there some way you can plug your gauge directly into the working ports that go to your cylinder? Try each one with the gauge acting as a plug, and see if you get the same pressures"



Please do not ever I MEAN EVER plug a port in a double acting cylinder with a guage, pipe plug or whatever.It could do serious damage to the cylinder and YOU! KABOOM!!!

This message has been edited. Last edited by: E West,

Going in the foward position I am hitting a block of wood and getting 500lbs pressure, when I retract the piston it hits the stop which acts as a quick load and shows me the higher pressure was around 1500lbs. Now since I have adjusted the loader on the pump I can make the retract pressure up over 200lbs, becuase it hits the stop and acts like a load for a second but my foward pressure is still at 500lbs. It sorta acts like the foward side of the cylinder needs a rebuild?

Thanks

EWest:

quote:

Please do not ever I MEAN EVER plug a port in a double acting cylinder with a guage, pipe plug or whatever.It could do serious damage to the cylinder and YOU! KABOOM!!!

Could you explain the reason for the "KABOOM?"

Over the years I have often plugged a port and pressurized the opposite port of a Single Rod Hydraulic Cylinder to check for Seal Bypass. NEVER, NEVER, NEVER had one go KABOOM or anything close to it. Maybe I was just being protected from Above!

The reason for plugging a Cylinder port was to check for Seal Bypass without disassembling the Cylinder.

To check the Rod End Seal of a Piston with Two Cup or U-Cup Seals, one for Extend, One for Retract, Plug the Rod End Port and pressurize the Cap End Port. If the Cylinder Extends the seal on the Rod End is bad since Bypassing Oil is getting past the bad seal and allowing both ends to be pressurized. Reverse the Plug and Pump Inlet to check the opposite seal.

On cylinders with a Single "O" Ring Seal, Bypass and Cylinder Extend will show up with either setup above.

This scenario works best with cylinders with Oversize Rods since the area difference allows more Extend Force. Also, any Cylinder load should be removed since a load can keep the cylinder from moving due to the lower extend force produced by this test.

At least that has been my experience.

quote:

Originally posted by E West:
Posted 03 September 2008 08:23 PM
"Is there some way you can plug your gauge directly into the working ports that go to your cylinder? Try each one with the gauge acting as a plug, and see if you get the same pressures"



Please do not ever I MEAN EVER plug a port in a double acting cylinder with a guage, pipe plug or whatever.It could do serious damage to the cylinder and YOU! KABOOM!!!

I should have made myself more clear. Put a guage on the working port of the valve that goes to the cylinders. Blocking one or both ports will open the relief valve built into all logsplitter valves, checking relief valve setting and/or valve bypass.

Regardless, a cylinder port can be blocked(for the reasons Bud pointed out), or is sometimes intentially or accidentally blocked during normal usage.

Anyway a new insight has emerged. when I extend to full stroke with no wood on the splitter and hold the valve in the foward position at the end of the stroke I get pressure around 1500lbs. So at full stroke and at full retraction stroke I get pressure. any Ideas

Since you can get 1500 PSI at full extend and full retract when the Piston is blocking the oil flow from getting back to tank I would say you have a Piston Seal Blown.

Checking as I wrote before would confirm the Seal Bypass.

If you don't mind wasting some oil, another way of checking the Piston Seal Bypass is to try to split a piece of wood, Return the valve to neutral then remove the line from the Rod end of the cylinder. Then shift the valve to extend the cylinder to see if there is flow out of the disconnected cylinder port.

If oil comes out of the cylinder port ou have a Seal problem.

So the 200 or 500 psi numbers were only while the cylinder ws moving? that would be normal, if that is all the load resistance. free moving or splitting some easy wood, very little load, little pressure is generated by the load.

If you get 1500 psi when stalled, at extend, and when stalled, at retract, either:
1. there is a leak across the piston seal, such that 1500 psi is enough to push the entire pump flow across the leak. Check it as bud posted.

or 2. The main relief valve in the lever (manual) valve is set to 1500 psi and passing flow to return. Adjust the main RV up.

k

I did the test as bud said to do, I put the piston in the full stroke outward then shut the motor off and pulled the shaft end plug. Then I fire the motor back up and pushed foward the control and got fluid out of it as I pushed it, Which I believe now to be blow back and I already yarded the piston off for a overhaul. Everything else seems dialed in and this seems to be the end result. As for the relief valve I am guessing that after you set this which is usually factory sent at about 2200lbs that is for forward and reverse?

Mark

Hey Bud

I told him not to plug the port because if he lets say plugs the rod side and then puts pressure to the cap side the oil obviously has nowhere to go.If the seals on the piston are working,and he keeps "givin it to er' " bad news. I saw this happen on an Enerpac 150 ton press.The customer said the press wouldn't come down so my coworker hit the buttons, pressure built up and KABOOM!!! The rod end coupler was loose so the oil could not escape. The cylinder blew apart, cracked from one end to the other. It sounded like a cannon went off.It took me a week to build him a new one!
Ellis

This message has been edited. Last edited by: E West,

quote:

Originally posted by Bud T:
Since you can get 1500 PSI at full extend and full retract when the Piston is blocking the oil flow from getting back to tank I would say you have a Piston Seal Blown.

Checking as I wrote before would confirm the Seal Bypass.

If you don't mind wasting some oil, another way of checking the Piston Seal Bypass is to try to split a piece of wood, Return the valve to neutral then remove the line from the Rod end of the cylinder. Then shift the valve to extend the cylinder to see if there is flow out of the disconnected cylinder port.

If oil comes out of the cylinder port ou have a Seal problem.

Much safer!!!

quote:

the rod side and then puts pressure to the cap side the oil obviously has nowhere to go.If the seals on the piston are working

good point, maybe needs further explanation. Just plugging the port is not good or bad. It depends on the state of the cylinder.


If the piston seals are bad, or even if there is very small normal leakage, the rod side port will only see the pump pressure. The leakage will actually be backwards, from the rod side to the closed side because of intensified pressure (continued below). Equal pressure on both sides of the piston (with unequal areas of course.) Cylinder acts like a simple single acting ram, with force out equal to the steel rod area pushing until the cylinder bottoms in extension..


If the Piston seals are perfect, and the cylinder is fully bottomed out, the rod side port would read 0, and force into the rod would be pressure times the full bore area on the closed side. This force is of course into the cylinder body, since I said it was fully extended and bottomed, so the force at end of rod is 0.


The dangerous situation is if the piston seals are good, and the Rod port is plugged with the cylinder short of full extension. Then there is intensification of pressure. Force into the piston from the closed side is Pressure times full area. Resisting force on the rod side is (smaller net area) x (unknown pressure). Since the forces must balance, solving for the unknown pressure is simply the area ratio of the cylinder. Typical cylinders, 1.3 to 1.5, but with larger rods, that could be 2 or 3 or even more. For example, a 6 inch bore with 5 inch rod would have closed side area of 28.3 square inches, rod side net area of 8.6 in2, and a ratio of 3.3. In that case, applying 2000 psi on the closed side would generate 2000 x 3.3 = 6600 psi on the blocked rode side. Ouch.... Either rod seal or tube may fail.


So the failure is not due to putting full pressure to the cylinder. Both sides see full pressure during normal operation. It is the intensification due to the blocked port and the area ratio. A counterbalance or flow control on the outlet (meter out) can do similar thing, so the loads and forces and pressures need to be checked anytime a meter out control device is being used.


Reversing the situation, blocking the closed end port, does not intensify because the area ratio is in the inverse direction: 2000 psi into rod side / 3.3 = only 600 psi required on the close side to resist the force.


Anyway, checking the piston leakage by blocking the cylinder at various points in the stroke would reveal the leakage, so it appears that is what you found.


BTW, just because relief valves are 'normally' factory set to xxx psi doesn't mean anything right now. It could be set anywhere, and you don't want to damage a new cylinder at startup. Back it out a few turns and set it after you put the repaired cylinder on. There could be dirt in it so it passes flow as very low pressure, dirt so it is stuck and passes at higher than normal pressure, or the fiddle factor by assorted owners or mechanics attempting to solve who knows what problems. Always assume it is incorrectly adjusted and check it. Very simple to check at stall.

kcj