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.

 

[mrcaptainbob]

Gees, this is going to be a messy job. No shutoff valves or filters to stop the gravity flow from the tank. An oil pan will be my friend.
Okay, let's suppose that I take that valve body apart. Is that even a wise thing to do? If I did that, what would I look for? Nicks? Some kind of deterioration some place? On the 'shuttle' or the body itself? Is there difficulty in reassembly? Chance of my nicking or scoring something?
So, what about that pump? Is it possible for it to pump intermittently? It hit high psi with an almost closed gate valve, but not knowing just how the internals work, well, I'm guessing and grasping here.
Is it possible for an air bubble? I did change the cylinder-return-hose-to-valve-body when the original burst. I did exercise the cylinder to expel the air. And the unit worked well for some time after that. Then, seemingly instantly, it just quit splitting.
Not afraid of any of the work, am mechanical inclined. Many rebuilt auto, tractor and mower engines rebuilt etc. And a fair machine shop in the barn.

 

[J_J]

Did you fully check out the cyl for bypassing.

If you almost closed off the pump flow and the pressure went up close to the rated value, it sounds like the pump is good.

Fully retract the cyl and remove the base end hose and try to retract some more and see if fluid pours out the cyl port, and if it does, the cyl seals are leaking.

If the pump is a two stage, it will probably start out at high flow and low pressure, and when the pressure gets to about 700 to 900 psi, the pump shifts to low flow and high pressure.

 

[Egon]

Can't really help on the valve but if you pull it apart things may become obvious.

 

[oldnslo]

Did you fully check out the cyl for bypassing.

JJ,
Good idea but captain has already done this. The problem seems to be in the directional control valve. With out having the valve in front of us it is a guessing game but it sounds like the casting is cracked or porous allowing flow to go from pressure to tank with very little restriction. He has an old republic (Teledyne republic) pump so not sure if if hi-lo or single stage. I can't remember much about these models.

Captain,
Tearing the valve apart may show you what the problem is. My guess is the casting is cracked or porous between the pressure port and tank port. If this is the case I doubt it would be repairable but it doesn't work now so tearing it apart could help confirm the diagnosis is correct before spending money on a replacement valve.

If the valve is mounted higher than the reservoir you shouldn't have to drain the reservoir to change the valve unless all of the swivel connections are below oil level.

 

[mrcaptainbob]

The pump is not a two stage, J-J. The tag lists but the one psi, plus I've never seen evidence of it changing power. As for verifying that cylinder seal.....Does it matter which direction it's checked? I verified the seal with the cylinder fully extended. Did that twice. Removed the return line at the cylinder and tried to force more extension and no oil came from the cylinder port. Putting the lever to retract the ram and gobs of oil came gushing from the hose. Would checking the opposite, as you suggest, show something different?
Egon, I hope y0ou're right. Surely nothing is obvious to me so far!
It just seems like there's a flow through somewhere and all the checks seem to come out okay. The pump blows a gate valve at 1800 or so, the cylinder does not appear to have an internal leak, and the relief valve, when over-shimmed, still does not provide pressure or relief at either extension or retraction. It does sound like a valve issue. I will check that by pulling the shuttle out and looking to see what the inside of a splitter control valve looks like. Always room for more edumacation.....

 

[Egon]

Just be carefull with those pressure checks. Sometimes the components turn into shrapnel.

 

[mrcaptainbob]

Well this was an effort in futility! Put a new valve on today. Brand new. The only difference between the old and new is the old had 3/4 in and out with 1/2 ports to the cylinder. All hoses are 3/4. The new valve had all four ports at 3/4. Although the cylinder in/out was a bit faster, there was not much difference in pressure. Still not enough to activate detent. There was just the slightest rise in pressure. The old at max out was 450, while the new is at 525 or so. I exercised the cylinder in/out at least a dozen times to evacuate the air and made sure to top off the hydraulic tank. So.....does a new valve need to be adjusted? Or is this pointing to ......an intermittent bad pump? Or....(open to suggestions..)

 

[mrcaptainbob]

About checking that cylinder.....Twice I extended the ram all the way out. Disconnected the hose on the ram end. Started it up and tried to extend the ram. No oil came from the port. Sounds like the cylinder seal is okay. But, is it possible that the packing inside closed off that port? Would it be better to block the ram at half extension and then disconnect the hose for the check?

 

[wdchyd]

Just pulling stuff apart is not a good idea.....you'll end up with multiple problems

You need someone with a flow load/meter to rule out pump flow and pressure before disassembling any components....otherwise you will just be spinning your wheels and digging in deeper

Sorry to be a broken record, but.........:confused2:

 

[J_J]

Your pump is bad.

If you say the cyl is good, and the cyl is what causes resistance to the flow to build up pressure, then one would have to assume that with a new good valve in the flow path, that the pump is not working correctly.

Recommend you take the pump to a hyd shop for testing.