Add a Double Pilot Check valve to Side Link Cylinder?

[MtnViewRanch]

If true that means 99.9% of the time a cylinder w/check valve should stop leak down.
I know installing top/tilt cylinders with check valves stopped the annoying leak down problem I was having.

You are correct. And we have gone over this before, the check valve limits what a person can do with the cylinders. If you have no use for the float function or if you do not have the float function with your rear remotes, then the DPOCVs are the way to go. :thumbsup: But if a person does have the float function with their control valves and does want-need to make use of that function, then the check valves take away that option. If a person has a good valve that leaks by very little, then that seems to work out well for them.

 

[MtnViewRanch]

I was thinking the same thing.

Manufacturers have a leak down rate for their valves and the dealer should replace the valve if it is under warranty, and leaking down more than the leak down rate.

I am sure the cyl manufacturer also have a leak down rate for their cyl.



I would say that the cyls are more at fault as people replace a lot more seals or cyl than valves.

Either one can be checked for proper operation.

All I can refer to is the thousand+ units that I have sold and had to deal with. As far as the cylinders being rebuilt more often, do you think that there is even a slight chance that is because that is the first thing people think about to fail, and don't even think that the valve is bad.

I am only talking about first hand experience here, not what I read about on the forums. All people have to do is a simple test of unplugging the hoses, be it for top & tilt cylinders or front end loaders, whatever. Most people do not do the test, they just assume that the cylinders are bad.

 

[wdchyd]

Correct me if I'm wrong but where did the OP say he HAD a check valve (single or double)....Most of you guys are assuming he has a check valve already and all he has to do is take off the hoses

He complains his cyl creeps bad enough that he cannot use his back blade

If troubleshooting consists of replacing valves 99.9% of the time and cyl creep is only from bad valves then all those people repacking cyls wasted all their time and money and only have to repack .1% of the time

:thumbdown:

 

[MtnViewRanch]

Correct me if I'm wrong but where did the OP say he HAD a check valve (single or double)....Most of you guys are assuming he has a check valve already and all he has to do is take off the hoses

He complains his cyl creeps bad enough that he cannot use his back blade

If troubleshooting consists of replacing valves 99.9% of the time and cyl creep is only from bad valves then all those people repacking cyls wasted all their time and money and only have to repack .1% of the time

:thumbdown:

We know that he never said that he had a check valve. He asked if he could put one on and was told yes. I said that if he unplugged his cylinder, he would know if it was the cylinder or his valves. If it is his cylinder, the check valve will do no good because it is leaking inside the cylinder.


As far as the cylinders being good 99.9% of the time, I am basing that figure from the over 1000 cylinders that I have sold and have had to replace 2 of them due to internal leakage. All of the other issues that might have come up, ended up being a bad control valve.

As far as wasting money on repairing the wrong thing, it happens every single day. And that is because people guess as to what is wrong instead of doing a series of tests to confirm what is wrong.

 

[J_J]

Agree on proper test.

What the OP said was that even the replacement cyl also creeped/leaked down, and he assumed that was normal.

I was told the leaked down rate for a particular cyl, but don't remember the rate of leakage.

In order to get a replacement cyl under warranty, the leakage rate must exceed the manufacturers published data.

It has been stated before that even with a good valve in neutral, the weight of an attachment can cause a cyl to bypass, either the piston seals or the rod seal.

If you had a good cyl, a good load could cause it to suck fluid through the valve spools and even possibly suck in air.

Excerpts:

***The second exception involves a load hanging on a double-acting cylinder (Figure 2). In this arrangement, the volume of pressurized fluid on the rod side can easily be accommodated on the piston side. But as the cylinder drifts, a vacuum will develop on the piston side due to unequal volumes, and depending on the weight of the load, this vacuum may eventually result in equilibrium that arrests further drift.

***If the cylinder is drifting but there is no equalization of pressure across the piston seal, the directional control valve or load control valve is the source of the problem.

I would say the ratio of cyl fail to valve fail is much greater.

 

[MHarryE]

This subject came up before and I answered with the allowable leakage for the most common flow control valve used on tractors and the like today. The simple valves are steel pollo in cast housings. Zero leak = zero clearance = zero being able to move the valve. So there is a slight clearance which results in slight leakage which increases with load. The manufacturers advertise the maximum leakage at a given pressure.

The manufacturers also supply zero leak control valves which incorporate the pilot operated checks in the valve but they are $$$$ in comparison. I once had a steer by wire machine, 4 wheel steer, in which the driver would often want to set the rears in a certain position for crab steer and would tolerate zero drift. The result and flow control valve was a maze of pilot operated checks, blew my budget, but was required to retrofit everything we had shipped. The next generation instead incorporated an electrical feedback loop that measured the offset electronically and automatically directed steering flow to keep the exact wheel position the driver ordered. It was less costly than the pilot check maze. And if cylinders leaked, that was also detected and compensated.

However cylinder leakage was rare - in fact I never recalled a problem on that machine. Cylinder seals are elastomeric and so rub against the rod creating a more or less positive seal because hydraulic power is available to move the rod. Operators are not comfortable with the added friction. Electric proportional valves are even less tolerant - we call it stiction. With added friction the current needs to overcome static friction (sticking) and the result is overshooting. Then comes the reverse signal to return where it should be and once again stiction enters in, overshoot, repeat. The goal is zero friction control valves to prevent hunting.

Here I am still talking about simple flow control valves. Hydrostatic transmission controls like the electronic control on a Kubota need super precision.

 

[bandaidmd]

I have Brians side link and it holds fine with the QC's disconnected.....plugged in it drops. I will be adding a pilot valve when i get "aroundtuit".
Myself and another member both based our builds off the same valve and we both have the same issue, for me I'm not ripping it all out and starting over the $89 lock valve will do.

 

[CJONE]

I would say the ratio of cyl fail to valve fail is much greater.[/QUOTE]

I have to agree with that. BUT when we start talking about cartridge or poppet valves all bets are off. They are not very reliable compared to a manual spool type valve. I have to use them in some of my systems when cost is a factor but they are not my first choice. CJ

 

[J_J]

You also have to look at the age of the remote valve compared with a new cyl, or using an old cyl on a new valve or a well used valve on a well used cyl.

Still, some simple test will determine the leakage of either especially with a load. .

 

[kcoburn]

Thanks for all the input. Let me fill you in on where I've been and where I'm trying to go.
My lane is 3/4 miles up and down along a river. Constant maintenance required. I had a Kubota L3600 with a single factory rear remote and a Monroe 7' HD backblade with a cylinder to rotate it(HEAVY). I added a 3 solenoid valve block plumbed off of the single rear remote. Initially used one position to operate an hydraulic top link and a second one to rotate the backblade. Bought an hydraulic side link through the dealer to allow me to tilt the blade for ditching along and crowning the lane. The cylinder would drop 3 or 4 inches in 10 minutes. Assuming the problem was the cylinder, they dealer gave me a replacement. Still leaked down so I gave up and abandoned it.
I've since replaced the tractor with a Kubota L5240 HSTC equipped with 2 rear remotes so I can operate the top link and blade rotation. Decided to try the side link (kept it when I sold the first tractor--not intensionally--forgot it). Turns out the L5240 has a smaller pin in the upper end of the side link, so I need to determine the right size and replace the upper ball end on the cylinder before I can determine if it can hold up the blade using the remotes on the newer tractor. Does anyone know a source for a new weld on ball end and the correct size for this 5240? The L3600 used a 7/8" pin, but the L5240's pin is smaller and uses locking nuts rather than a pin as a retainer.
Reading through all your responses leads me to conclude that the problem with the original setup was in either the remote on the L3600 or the solenoid diverter block. I want to confirm that the side link will perform satisfactorily through the L5240's remotes. If so, there'd be no need to add a check valve to the cylinder. If I can make this work I may spend the horrendous $ Kubota wants for the kit to add the 3rd remote.
Thanks again for your help. Now I need to find a source for the correct ball end for my cylinder.