Thumb Valve Leak Mystery

[J_J]

If the PRV is leaking, yo need to fix it first. It might look like this. Use for ref only.

http://www.princehyd.com/Portals/0/products/valves/RD2500InstS.pdf

You can also tee in the gage at the input to the BH valve or the FEL valve to monitor and trouble shoot the hyd system.

Anytime you use the hydraulics, the fluid will flow through the tee and reflect the pressure on the gage.

 

[mmranch]

Thanks very much for this JJ!

From the looks of it (just looking at the body style... I can't see any model # yet as it's so tight against the BH control tower), I think the valve I have is the RD4100:

http://www.princehyd.com/LinkClick.aspx?link=products/valves/RD4100Manual.pdf

This looks like mine including the pressure relief valve portion.

Ideally, I'd like to have permanent gauges... but I don't think I'm that good yet to do the modifications!

According to the drawings...shouldn't I be able to simply remove the PRV (not adjust the adjustment screw yet) and replace damaged o-rings then re-install and it would be operational at the original setting?

Thanks again!

 

[mmranch]

I'm 99% sure this is the RD4100. My dealer (who I haven't yet heard from on the issue) received and installed the valve. The valve data shows a number of options and I don't know if all these options come with the valve as standard and you simply install what you want or if you have to order the options.

In any event, there are two options for the PRV:

1. No PRV
2. PRV 500-1500psi - factory set to 1000psi
3. PRV 1500-3000psi - factory set to 2000psi

I know I have one of the adjustable PRVs... just don't know which one.

I pulled the PRV and there are two o-rings... a round and a square. There is some slight damage to both it appears (tiny slivers of o-ring removed).

Guess the only way to tell what PRV I have is to test with the gauge when I get it. Will keep you posted.

Thanks again to all.

 

[mmranch]

OK, I replaced the #6 o-ring (see attached image) on the PRV and re-installed but no joy. The PRV is still leaking from the hex screw area. (I haven't been able to find the #5 flat rubber o-ring yet. (Neither o-ring really seems that damaged).

Since it's a cartridge and doesn't show any exploded view, do I need to replace the cartridge? That could get pricey if this happens often. Can these cartridges be disassembled and is there replaceable parts inside? Not sure where to buy the cartridge as the Prince website doesn't seem to have ordering of parts.

Since the leak is happening at the hex screw, the fluid is obviously passing through the center of the PRV so it would seem it's something inside that's amiss.

 

[Don87]

Pic says the 'relief cartridge' is on page 5..........what does page 5 say, or show?

 

[mmranch]

Don,

Page 5 just shows the same image of the 3 cartridge options... no exploded view of a cartridge. It shows:

1. No PRV cartridge... it's just a plug.
2. PRV 500-1500psi - factory set at 1000psi
3. PRV 1500-3000psi - factory set at 2000psi

The two PRV cartridges are visually identical in the drawing and there's nothing inferring taking them apart in any way. So there's basically no info beyond that there are 3 options and that you can adjust the pressure via the hex screw.

My question is, what have other's experiences been with these cartridges? Are they disassembleable? Do you just bite the bullet and order a new one?

I assume that there's stuff inside... such as a spring or something but I'm a little leary of taking it apart until I hear what others have to say.

 

[J_J]

I am thinking someone, awhile back, rebuilt one of these relief cartridges. I believe he opened it up and did some machine work and replaced something, and put it back together and it worked. Does anyone else remember that post.

 

[mmranch]

Thanks for the ideas JJ.


It's amazing to me how this mystery has evolved over time... let's review:

I order a new TYM backhoe with my tractor and want a thumb on it. My dealer gets and installs a Wallenstein thumb on the backhoe which comes with a Salami spool valve for the thumb. Works fine for a while but then begins to leak from the spool. Dealer gets a replacement valve from Wallenstein which is an identical Salami valve. Shortly, it begins to leak from the spool. I then pull out the spool to find the o-rings damaged. Each time I replace the o-rings only to have more leaking in short order and more damaged o-rings.

My dealer then installs a Prince RD4100 spool valve which works great for many months with no leaking. He tells me when he delivers the replaced thumb valve that there will be an occasional screeching sound and there is. Sometimes when operating the thumb, there is a screeching sound (even if there is no load on the thumb)... not each time it's operated... just sometimes.

Then recently, the Prince RD4100 valve starts leaking through the PRV... not around the PRV but straight through the core and out the adjustment screw. Upon investigation, I find that this valve has a number of options including 2 different PRVs... 500-1500psi and 1500-3000psi. (I have not found any model# info on the valve yet so I can't determine which PRV is installed and my newly ordered gauge hasn't arrived so I can't check it that way yet).


I want to make sure I understand how the pressures and the PRVs are supposed to work before I start ordering a new one so I can get the proper one I need.

Let's say in theory my tractor is putting out 2200psi at the rear remotes. The two backhoe hoses are connected to the rear remotes. The backhoe valve presumably has a PRV and it's set at 2000psi (in theory) (NOTE: the BH itself has been operating fabulously with no problems). The thumb valve is connected to the BH valve (at power beyond port?) and the thumb valve has it's own PRV which we'll say is set to ?.

So if I understand how a PRV is supposed to work, the PRV limits the pressure going into a valve and any device connected to that valve (such as a backhoe cylinder) to prevent potential damage to the valve or device. So when the PRV activates, it merely bleeds off excess pressure fluid (which is returned to the tank)... the PRV itself is not supposed to leak OUTSIDE of the valve. So my leaking PRV is broken in some way and I need a new one or repair the one I have.

But does it seem like the pressure is set too high or two low on the different thumb valve's PRVs? Blown o-rings in the Salami valves originally might seem like pressure set too high? The screeching of the new thumb valve might seem like pressure set to low?

Screeching on the new valve seems like maybe the 500-1500psi PRV is installed (factory default setting of 1000psi). Just wondering which PRV option to try an order.

Ohhh... and there's a third option on the Prince RD4100 valve which is a simple plug - no PRV at all. The thumb cylinder is a 2 1/4 size so if there was no PRV, then the BH valve PRV would be limiting the pressure to 2000psi?

Then there's ordering the parts themselves... haven't found any websites yet that list these PRV options... sigh.

Thanks for listening to me ramble!!

 

[mmranch]

OK, an update.

Yesterday, I had some digging to do and before I started, I turned the PRV adjustment screw 1/4 turn CW (increase pressure) and the leak stopped and didn't leak while I was working. Will watch to see if it's stopped completely.

I also found in the Prince documentation a cross section drawing of the internals of the PRV cartridge and it appears very simple. Basically just a spring holding a stopper and the adjustment screw tightens the spring putting more force on the stopper. The adjustment screw pushes a thing which pushes the spring. The thing looks like it might have an o-ring that seals, so it might be another o-ring to change.

Thanks again to all for the ideas!

 

[J_J]

By turning the screw down, you may have set the BH PRV above the FEL PRV setting. It should be equal to or lower than the FEL PRV. I would put a gage at the input to the BH, and check/adjust.

 

[wdchyd]

I am thinking someone, awhile back, rebuilt one of these relief cartridges. I believe he opened it up and did some machine work and replaced something, and put it back together and it worked. Does anyone else remember that post.

Yes, I remember commenting on this subject before.........these cartridge valves are not suppose to come apart but can be unscrewed by using the jaws of a lathe to grab the area where the oring is......them loosen the hex to expose a hidden oring internally in the cartridge.....it's the oring on that stem that is leaking......

Regarding the perpetual leaks that the OP'r is running into, there is an elevated return pressure downstream of this valve......it needs to be a power beyond type valve to deliver downstream pressure to the next valve, separate from return to tank flow.....

the orings on his valve and the oring in the PRV cartridge is seeing the high pressure from a restriction or the next valve inline.....resulting in oring failure every time......these orings are not suppose to see high pressure, only low pressure from return flows to tank......

NEEDS PB VALVE......

 

[J_J]

If all else fails he could seal up the relief port and install an external relief valve before the FEL valve.

 

[wdchyd]

Yes, that could be done but the high return pressure oil leaving the valve housing is what's causing the root problem here, the high pressure oil in the PRV does not see that oring, only the return pressure, ......and the orings will still develop leaks at the valve spools in time if the PRV is plugged off.....

IIRC in this thread it has been a recurring problem, I think the valve has too much downstream pressure on the return side......PB valve needs to be installed and plumbed in or there is a restriction in the return side (fitting too small) if a PB valve is in use.....

My bet would be this is a regular valve installed inline with another valve (3PH, BH )or something else downstream..........:confused2:

 

[mmranch]

Thanks to all for the ideas! This is getting a bit complex for me to understand but I understand the basic concept that maybe high pressure fluid is getting to where it should be low pressure fluid.

A few more tidbits.

When I spoke with my dealer, I mentioned that I had turned the PRV adjustment screw 1/4 turn and the leak had stopped (the leak has not leaked since). He mentioned that he had spoke with a tech at Prince and that person said that sometimes if there's not enough pressure on that spring in the PRV, it will leak and that tightening it a bit can fix the leak (not very scientific I know).

I also found in the valve docs a cutaway drawing of the internals of the PRV cartridge itself and it seems very simple. Adjustment screw presses against a plunger (my term), which presses against the spring, which presses against another plunger which is where the relief happens. The first plunger appears to have an o-ring which seems to be where the fluid would be passing to leak down the adjustment screw.

This is my crude understanding of how the valves are setup: two hoses connect from the rear remotes of the tractor to the BH control valve (I assume that maybe there's a PRV for the BH on this valve inside the BH console). There are hoses that come from the BH control valve to the thumb valve and this thumb valve is mounted on the outside of the BH console (it is enclosed in a bracket and only it's spool and PRV are really accessible without unbuilding the bracket and BH console). The Prince RD4100 thumb valve has a number of options including a power beyond port but it is plugged.

So as far as I understand, it's tractor>BH valve>thumb valve.

I recently received my pressure gauge but have not used it yet. If I plug it into the output rear remote, won't that give me the pressure that the tractor is putting out? Do I need to do something to make the pressure go to the max or is just plugging in the gauge enough to read the max pressure?

If I plug in the gauge at the thumb cylinder, won't that show me the pressure that the thumb valve is putting out?

These two places and the FEL connections are the only places I have QDs to plug in the gauge.

Got to get to work.

Thanks again!

 

[wdchyd]

So as far as I understand, it's tractor>BH valve>thumb valve.

After the thumb valve does the flow go directly to tank or into the 3PH..??

My theory is that the return pressure coming out of the thumb valve is too high....resulting in premature seal failure....Yes/No..??

 

[J_J]

wdchyd,

If the fluid from the BH is going to the 3pt, then when the 3pt is is fully stressed out, lifting max load, then there is a good chance that there is high back pressure being felt on all the valves.

 

[wdchyd]

JJ,

That's exactly what I'm saying.......the max pressure on the 3PH will show its ugly face to those seals that are failing from back pressure.......:thumbsup:

Of course that's assuming it's going directly to the 3PH w/o PB......:confused2:

 

[wdchyd]

another thought is my BH for example doesn't use the 3PH cuz it's locked out when the BH is mounted on the back......

so in my case there's no need for PB on a BH valve bank if the 3PH is not in use.....thus no back pressure to the BH valve......

I just wonder if the OP'r has his thumb valve upstream of the BH control valve.....it might be a good thing to confirm or deny......

 

[J_J]

mmranch,

You said:

The Prince RD4100 thumb valve has a number of options including a power beyond port but it is plugged.

So as far as I understand, it's tractor>BH valve>thumb valve.


Why are you not using the PB from the thumb valve to go to the 3pt. You seem to be using the OUT/TANK port to send fluid to the 3pt, and if that is true, you are providing the thumb valve with to much back pressure whenever you use the 3pt. That is not good for the spools and the relief valve, depending on the thumb PRV setting. I would set all the relief valve the same.

You should have a series connection like this. Pump, FEL, BH, THUMB, 3pt. You should be using any PB port available to feed the next valve, as this port can handle the high pressure. .

 

[mmranch]

Thanks for all the ideas on this!

After getting my tractor out of the bog it was stuck in today (I hate when that happens), I finally can now upload some photos which may shed better light on the situation (see attached images of BH console).

I opened the BH console today to see how things were setup. It turns out that it is setup like this:

tractor rear remote > thumb valve input > thumb valve output > BH control valve input > BH control valve output > tractor rear remote.

So the thumb valve is first, then BH valve. My dealer set things up this way. At the moment, the thumb valve PRV has not been leaking... but I haven't put sustained heavy use on the BH since I slightly turned the adjusting screw.

Thanks again.