Valve eating O rings?

[Natman]

I started having intermittent issues with my rear down function outrigger, that eventually got worse and worse. So, not knowing any better and being in a hurry, I took the 30 ton National to my local CAT shop. They are of course the most expensive route, but they are 1 mile away from my yard, and I know the service manager and he gets me in and out ASAP, meaning the work I don't miss makes up for their premium expense.
So, they quickly determined the cause was the valve for that function, and the next day the new complete part came up from SLC and I was good to go before noon, and made my already scheduled job at 1. A couple weeks go by, and the same thing happens again, but this time I have a spare valve (cartridge?not sure of the the terminology) and as I had streamlined the process of removing the rear cover (putting disconnects on the wires going to the lights, backup beeper, etc., so now I can set it out of the way rather than work constricted by it) and in 5 minutes the 2 week old one was out and another new one in place and again I was able to meet my work schedule. But now I see the removed valve is missing a teflon ring on the bottom of the O ring and the teflon ring on top is half broken.

So, FINALLY wising up, I get the parts book out and order just some rebuild kits, not the whole valve, which I assume are the two teflon rings and the special O ring. I say special because of it's cost, who knows? But the issue of it eating these rings is what concerns me, and I don't like the idea of them floating around in the hydraulic system either. At least now I know I can fix it quickly onsite and not be stranded somewhere with a down outrigger, but something ain't right.

 

[crane operator]

I'm going to assume this is a electric dc controlled solenoid valve? There's a little black electric magnet that fits over the silver stud that's in your hand? The teflon backers that are broken, are they on the two o rings that are visible, or is there one that's missing?

Are there only o-rings where the blue arrows are? or is there another one where the red arrow is?



I'm not really sure what would be taking them out, unless its loose in the bore, or that the bore that it threads into has a bur, or is cracked. The o rings shouldn't move in there once its tight, so there nothing for them to rub on.

I'm going to throw out a option. I have seen the dc magnet solenoids get bad, and then they get really really hot. This is usually on one that stays open all the time, like the ones that hold open the a2b shut off controls. If it was getting super hot, I could see maybe cooking out the seals. Or hot enough to be brittle. Usually the solenoids just quit working correctly when they get bad. So I'm not convinced that's the problem. But you could put your hand up by it and see, just be aware its like mcdonalds coffee, it can be hot.

Maybe a test light in the dc control magnet to make sure its only energizing when its supposed to be, and you don't have a swivel wiring issue making it stay open and deadheading the hydro, but I would think you would hear that.

I think I'd pull out the valve body/ bore piece, and give it a good looking over for a crack in the aluminum. Its probably part of a stack, and its probably buried, but I think that's where I'd look. Hairline cracks can be hard to see in the body, but I've had them crack from vibration if the body bolts get loose.

 

[Natman]

Yes, a coil goes over it, 12 VDC I assume. The big O ring at the base of the threaded portion is and was OK, NO O rings where the red arrow points. I have an additional brand new still in the box valve to confirm this. Good idea on checking it for excess heat, when it should be passive, and that will be easy to check. IF there is a next time, I will take my borescope, normally at home, and if I'm not in a big rush see if I can find anything that looks like it may be cause of the problem. Otherwise, I'll just keep a supply of the teflon rings, O rings handy. What gets me is my supplier ( a National dealer) is not set up to use the postal service, so in a couple days I'll get a half dozen or so (I ordered 3 repair kits, plus I have the new unused complete assembly) O rings and teflon rings, that could have easily been mailed for whatever a stamp costs these days, when the big brown truck drives up, just seems a waste of resources but that's the way it is. Especially as I live at the end of a very rural road up a mountain, with a large mailbox, oh well! Thanks for the advice.

 

[heymccall]

Could the backup ring be on the wrong side?

 

[terex herder]

Maybe set down with a hydraulics catalog like Hercules and find a seal that doesn't use the teflon rings. A one piece non-split may be more robust than the teflon.

 

[Natman]

The new/unused complete valve I have uses two teflon rings, one above and one below the 0 ring, and I can only assume it's correct. For the same reason, I'd hesitate to change anything. Who knows, maybe it the issue will go away, I'm just happy to have enough of a handle on it to not have to worry about getting stuck somewhere out of town at the end of a long day, with a down outrigger!

 

[Dave Neubert]

A lot of the back up rings are split look at the old one and see if it is cut at a angle I would also do a pressure test on the out rigger system

 

[Natman]

Yeah the new ones are split. Besides totally missing one on the valve i took out, 2 weeks old, the other backup ring was missing a large chunk, like something had been chewing on it.....

 

[Dave Neubert]

High pressure will eat up o rings were the old o rings hard or still pliable

 

[Natman]

Didn't get to see the original valve, the CAT shop bought new and I didn't think to ask to see the old one. But the one I'm talking about, with one teflon ring totally missing and the other with a piece broken out, was only in there 2 weeks! It's the one in the picture.