DPOCV supplier

[AKKAMAAN]

the way tilt cyl is hooked up, gravity load pressurizing the rod side of piston, a DPOCV, wont be any full guarantee, preventing for drifting....only if gravity load hangs on the capped side....
This because if piston seal leaks, volume from rod side will fit into capped side, and the void will create vacuum....
An arrangement with DA Cylinder lifting with the capped side will be "drift free" with a DPOCV...

The way it is hooked up, you only need a single pilot CV for the rod side....

 

[AKKAMAAN]

I'm not sure why this is happening, but it is. SCV's are brand new and hard piped by the dealer, and shouldn't be leaking down like that IMO. Could be the new cylinder, I suppose. I used a 1.5"x6" for the HSL, and a 2"x11" for the HTL. Of course the top link has a DPOCV so it stays exactly where I put it.

You will always have more leakage in the CV (both spool and the work port PRV) than through a brand new piston seal

It's a personal thing, I guess. I just hate droopy hydraulics. I thought it might be sucking air somewhere, but it's dry as a bone under pressure, and we're only talking a set of QC's, two 36" hoses, and a cylinder in the entire loop. Any kind of leak should be obvious.

P.S. Don't say it, MVR. I already know your opinion of DPOCV on side links. :laughing:

http://www.tractorbynet.com/forums/hydraulics/185353-dpocv-supplier-2.html#post2112671

 

[picker77]

Hmmm.... yep, it's installed with the rod end down, mainly because that way I could do the clevis welding out on the rod end and didn't have to heat up the body of the cylinder.

So, I could get away with just a single in-line pilot operated check valve on the rod end? If so, the price goes way down and I know where I can get those.

AKKAMAAN:
"The way it is hooked up, you only need a single pilot CV for the rod side.... "

 

[AKKAMAAN]

Hmmm.... yep, it's installed with the rod end down, mainly because that way I could do the clevis welding out on the rod end and didn't have to heat up the body of the cylinder.

So, I could get away with just a single in-line pilot operated check valve on the rod end? If so, the price goes way down and I know where I can get those.

AKKAMAAN:
"The way it is hooked up, you only need a single pilot CV for the rod side.... "

Yes , because your problem is CV leakage, and if piston sel leaks a double wont do any good any way......well 15psi difference....the vacuum pressure on the capped side....

EDIT:Rod up or down does nopt matter, it is a matter of if the load resting on capped side or rod side pressure

 

[picker77]

Akkamaan, will this one do the trick?

https://www.surpluscenter.com/item.asp?item=9-7933-6-65&catname=hydraulic

 

[AKKAMAAN]

Akkamaan, will this one do the trick?

https://www.surpluscenter.com/item.asp?item=9-7933-6-65&catname=hydraulic

That one will do a trick for you, but not the desired trick....need to be pilot operated...like this one...
It is no biggie....you can use a double one too....by I thought a single could save a few bucks...

 

[oldnslo]

One item to consider is using DPOCV on a cylinder is thermal expansion. If you operate the tractor when cold and then let it sit in the sun you can trap and build some serious pressure in the cylinder.

Roy

 

[picker77]

That one will do a trick for you, but not the desired trick....need to be pilot operated...like this one...
It is no biggie....you can use a double one too....by I thought a single could save a few bucks...

Ok, but on the Brand PC valve you pointed out (photo one) the pilot port would still have get cracking pressure from the other end of the cylinder, so it would have to be teed into the capped side of the cylinder. Right?

If so, then the single piloted check in photo two would do exactly the same thing, although because the pilot fluid's path is internal, the valve and its external plumbing would still look like the usual top link DPOCV setup (photos three and four). However, the valve itself should naturally be somewhat cheaper than the double version, and only one end of the cylinder would be locked. Correct?

Sorry for the high density of my brain cells on this subject. I've worked in electronics for 50 years, so I can do that in my sleep, but I've only played with hydraulics for a few weeks, and it's like first year algebra to me. :laughing:

 

[J_J]

That is correct, but the pilot to the PCV comes from the work port for that cyl. There may be a small delay before the cyl moves, because it also has to overcome the pressure from the implement if any.
What is the static cracking pressure for your PCV valve?

This valve is a DPOCV from Surplus Hyd

https://www.surpluscenter.com/item.asp?item=9-5606-50&catname=hydraulic

Also click on More Specs

The pilot ratio is 4 : 1

 

[picker77]

That is correct, but the pilot to the PCV comes from the work port for that cyl. There may be a small delay before the cyl moves, because it also has to overcome the pressure from the implement if any.
What is the static cracking pressure for your PCV valve?

The one I've been looking at is 3 bar, or about 43 psi. It has a 1:5 ratio. But I'm not sure exactly how that applies in the actual operation of the valve. Sounds like it means that for instance if my available system pressure is 2200 psi, the check valve would begin to open when pressure from the SCV exceeds 43 psi, and be wide open from 440-2200 psi, begin to close again below 440 psi, and be fully closed again at 43 psi?

Also, I've heard the term "chatter" bandied about in regard to DPOCV's. What causes it, and what's the cure?

And thanks again to you guys for the education. :thumbsup: