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.