No cylindder pressure....

[oldnslo]

It's a Republic pump. Not sure of the first character, I think the info is:
Model: 0212 3S2 AB
RPM: 2000
PSI: 2200
cu "/rev: .364
It appears there is oil movement in all positions. I presume I could verify by removing the line to the tank in port.
Frankly, I was VERY surprised to see the pump shaft had been damaged at least twice before. I'm sure that shaft originally had but one key way. It got buggered up, then a new one was cut. And that was buggered up too! And...the key was sheared. So I cut yet a new key way and made up a new 'key' for it. And since the old set screw could not be removed, I drilled/tapped for two 1/4-20's at the 120* positions from the key slot on the coupler. It's nice and snug now. I am astonished that the pump would meet such a load so as to rip that key through the shaft! I would have thought something else in that pump or hydraulic line would have gone first.

Shaft damage usually indicates over torque or severe shock loads. Since it appears this pump is rated to 2000 RPM how is it being driven? Direct coupled to an engine running at what RPM? Most small engines like Briggs, Tecumseh etc operate around 3,000 t0 3,600 RPM.

Pressure of 2200 PSI. Since you don't have a pressure gauge does anyone know what the relief valve was set at?

Republic or Teledyne Republic was purchased by Parker Hannifin Corp. many years ago. I suspect this is a gear style pump but not positive.

Sounds like the time has come to start isolating components to see where the problem lies. First component would be the pump. If you are comfortable doing the procedure that JJ suggested in plumbing a Relief in the pressure line along with a gauge, this would indicate whether the pump can generate flow under pressure. If shaft had been damaged at least twice I am starting to suspect your pump is damaged.

Quick and simple test. Run the cylinder until it bottoms out then hold the directional valve so it should be still trying to move the cylinder. Feel the pump does it get very warm or hot quickly. If yes this would indicate the pump is bypassing internally and is probably part or most of the problem.

 

[mrcaptainbob]

Well, Oldnslo, that preliminary test does show the pump to get pretty warm. The pressure gauge I ordered has yet to arrive. I won't be able to get to this project until next week some time. Two things....(consider I don't know much about these pumps...) is it possible to clean up the vanes in it and turn them over to the unused side? I took one apart a couple years ago and did that because the vanes were stuck with varnish. Wondering if this could be the same. The second question is, should that not be a good idea, then is a rebuild kit available for something like this? Again, it's a Republic pump, model 0212 3S2 AB.

 

[Egon]

(Quick and simple test. Run the cylinder until it bottoms out then hold the directional valve so it should be still trying to move the cylinder. Feel the pump does it get very warm or hot quickly. If yes this would indicate the pump is bypassing internally and is probably part or most of the problem.)

In this scenario the pump will get hot indicating it is working.

If it doesn't get hot it's not pumping fluid.

 

[oldnslo]

(Quick and simple test. Run the cylinder until it bottoms out then hold the directional valve so it should be still trying to move the cylinder. Feel the pump does it get very warm or hot quickly. If yes this would indicate the pump is bypassing internally and is probably part or most of the problem.)

In this scenario the pump will get hot indicating it is working.

If it doesn't get hot it's not pumping fluid.

No,
If the pump is pumping fluid correctly it will stay much cooler than if it is bypassing internally which creates heat. By passing pump is like a relief valve. The fluid keeps circulating in the pump and fresh cool fluid does not get drawn in to take the heat away.

Mrcaptain,
If this is a vane pump it is possible one or vanes are stuck. In my experience with Vickers vane pumps the vanes were not reversible. I do not know how the republic pump is made. If the vanes are sticking cleaning the varnish would certainly help. On Vickers the vanes are forced out against the cam ring by centrifugal force on the suction side and them some working pressure is applied to the back side to hold them in place against the cam ring as the pressure builds. Again not sure how Republic it made.

 

[mrcaptainbob]

First...I hope you all had a Happy Thanksgiving. (I'm still full!)
Second....here's an update on this splitter's lack of pressure...I installed (from the pump...) a 5,000 gauge, then a gate valve, then the splitter's valve body. With the gate valve open and the oil somewhat warmed up and th cylinder moving it was zeroed out. With an 8" log on and holding the lever it continued to slowly build pressure to around 450 psi. Hmmm. So I put it to close the cylinder and it went to detent. In that position it built pressure to around 150psi. The splitter valve was manually returned to center. Then I started closing the added gate valve. It started building pressure! I stopped when it was around 2000psi! (The gate valve's threads cracked. Yeah...I know....But I don't have a steel valve to use...).
I assume from this that the pump is good? So what's my next step? Put shims under the relief valve spring? Would the 'O' rings in the valve body need replacing?

 

[oldnslo]

From what you are describing their is a major leak path in your directional valve. Not to be negative but are you sure you removed the relief valve and reinstalled it correctly in the directional valve. Is there something stuck on the relief valve seat or is the poppet damaged and not seating. If this is a pilot operated relief the pilot hole could be plugged or the pilot poppet could be held off of the seat. Both of these would cause the low pressure you are seeing. There are no seals on the directional valve that would allow this much leakage. The seals on the valve prevent oil from leaking out around the end and dripping on the ground.

Do you have the capabilities of posting a couple of pictures of the directional valve. Also post some pictures of the relief assembly removed from the valve body. Sometimes a picture is worth a thousand words.

 

[mrcaptainbob]

I've been having 'puter issues with posting pics lately, Oldnslo. But what you say makes much sense. I'll disassemble the relief components again and inspect them all with much more care. I plan to start the unit and let it flush any possible contaminants out. Then inspect the seat with a flashlight to verify it is sound. Reinstall it all and start the unit again. If nothing, the next will be to shim the spring. Verifying the pressure gauge for any positive changes. If there are changes, is it possible to find a new spring? Or will shimming be adequate? I would shim it to 2000psi, as the pump is rated at 2200psi. If this all fails, then it's time to replace the whole valve assembly.

 

[Egon]

As mentioned disconnect the discharge hose before the control valve and check for flow. After you get flow start looking at the splitter control valve.

:

Hmmm!:

 

[mrcaptainbob]

I installed the gauge right at the pump output port. The pressure at full extension is 250 and, after about a minute or two will advance to 450. And it also changes engine rpm's a bit. The return detent does click off around 250psi. Pressure at center is 150. I checked the relief valve again and inspected the seat. No visible signs of contamination or nicks. The ball appears good. I added a split washer at the cap end of the spring. That made absolutely no difference. Pressure readings at all positions were the same as without the added 'shim'. After full cylinder extension I removed the retract hose from the retract port of the cylinder. Setting the valve to extend the cylinder showed zero oil coming from that port, telling me the shaft seal must be okay. Putting the valve to return and oil gushed from the return hose, as expected.
So.....did Egon nail it? New valve time?

 

[oldnslo]

Captain,
Without physically looking at your hard it is very hard to say what is failing. It is rare for valve bodies to fail but always possible and from what you are describing it sure points that direction.