Top Link Hydraulic Cylinder Woes

[augerin]

I am going to operate the thing to temperature and then dump oil into a clean pail via the SCV and a hose to see if air is present.

I spoke with my wonderful Mennonite JD experts and they kind of alluded to the fact that they might know what is going on and I should bring it down. I would like to see the air for myself first. Then, I could check after as well.

As has been mentioned, a hydraulic pilot-operated valve or load check valve will solve the issue. The hydraulic system itself doesn't offer much resistance to change fluid can pass if enough external pressure is applied.

Hydraulic Pilot-Operated Check Valves | Flowfit
Check Valves

 

[MtnViewRanch]

Your valve is leaking.
You need check valves.

TOP-N-TILT

OSHA requires them in most cases for top links.

Please show us that requirement with an OSHA reference number. Not something that Haytools shows. DPOCVs are required when there is overhead lifting done and specifically where there could be people below in normal operating conditions.

If what Haytools says is true, then ALL front end loaders would have them, they DO NOT.

Do you really think in this time of sue anyone for anything that JD and Kubota would sell their factory top & tilt sets without DPOCVs if it was mandated by OSHA that they be there?

I don't think so. :confused2:

 

[MtnViewRanch]

As has been mentioned, a hydraulic pilot-operated valve or load check valve will solve the issue. The hydraulic system itself doesn't offer much resistance to change fluid can pass if enough external pressure is applied.

Hydraulic Pilot-Operated Check Valves | Flowfit
Check Valves

A check valve will not prevent the squish. Either there is fluid in the cylinder or not. If there is any air in the cylinder the check valve has nothing to do with what happens because of the air in the unit.

 

[LD1]

I still haven't read about load check valves; it should have them, or a similar system, so that when the cylinder isn't being moved up or down it is effectively locked.

Check valves won't allow you to use float.

I have a need for float on my toplink. If I did not, then yea...check valves would work.

When you have something heavy hanging back there....you have ALOT of leverage/force trying to extend the cylinder. Combination of valve leakage and a little seepage by Piston seals and you cylinder drifts. This causes a vacuum or air in the system.

So you have your blade or rake hanging off the hitch.....it drifts a little....now you lower it to use it and you have a spongy cylinder because you didn't cycle the toplink to purge the air.

That's one cause. The other, as mentioned, is a pump that isn't filling the cylinder as fast as gravity wants it extend it. Those with loaders and no Regen... It's a common issue here knows as floppy bucket syndrome.

Drift and leakage by valves and internal seals is just a part of hydraulics. The only dispute is how much leakage is considered acceptable.

To prevent a squishy cylinder, you have to prevent air from getting in. If air is getting in because of drift....DPCV's and a good quality cylinder (quality seals). If air is because fluid isn't entering fast enough....restrictors.

 

[Industrial Toys]

Like so many things, 12 volt electrical issues in particular, often you have more than one issue going on. Like I said, first I will inspect the fluid for air. As LD 1 described with the pulling (vaccume) and pushing, I was certain this was my problem particularly on account of my undersized top link cylinder. With the new 4" top link, this seems less likely.

As for Hay Tools and the OSHA requirement, I too, questioned that. Had a check valve been available from Jaymar (Makers of New Top Link) at a modest cost, I would have gone for it, but it wasn't.

4" custom made top link was $204.00 CDN, (13% tax in) . Not too bad. I told them I wanted 22" c to c closed and make the stroke as long as you can. Ended up just under 11". Good, but would have preferred a little more as with my old link. ORB # 8 Fittings.

 

[Ricn]

Maybe try putting a lock out valve in the line? I had this issue with my flail mower being so heavy the Tilt cylinder leaked off tilting the mower all the time. The lock out keeps it level now...

Ricn

 

[LD1]

I know they are expensive. But flow controls would do wonders. A 1/2" flow control valve is something like $40 each, and you need two.

But the flow control valves can do the same thing a dpcv AND restrictors do.

Shut them off for transport, and they are like a check valve totally isolating the cylinder from the rest of the system.

And can meter flow as to not have gravity act upon the cylinder faster than it can fill.

Beyond that, if there are still issues, it's likely due to a cheap cylinder with cheaper seals. Cause nothing can prevent a cylinder from drifting in the extend direction 100%. Retract....yes, but extend, you are at the mercy of the gland and Piston seals. And as I said, they all leak over time, how much so and what is considered acceptable....that is up for debate.

 

[npalen]

Brian and the rest of you guys:
I wonder if restrictors at both ports tends to be counterproductive IN SOME CASES. I can certainly see the need for a restrictor at the rod end for safety as well as controlling outflow to allow the pump to keep up. A second restrictor in the base end of the cylinder, however, would seemingly make it more difficult for the pump to keep up when extending the cylinder with a heavy load. I say this because the pump has to provide more pressure to overcome the restricted flow while trying to keep up with a heavy load forcing fluid thru the rod end restrictor. Again I'm saying this might occur in some cases.
What are your thoughts?

 

[MtnViewRanch]

Brian and the rest of you guys:
I wonder if restrictors at both ports tends to be counterproductive IN SOME CASES. I can certainly see the need for a restrictor at the rod end for safety as well as controlling outflow to allow the pump to keep up. A second restrictor in the base end of the cylinder, however, would seemingly make it more difficult for the pump to keep up when extending the cylinder with a heavy load. I say this because the pump has to provide more pressure to overcome the restricted flow while trying to keep up with a heavy load forcing fluid thru the rod end restrictor. Again I'm saying this might occur in some cases.
What are your thoughts?

I 100% agree with you in theory, but I know for a fact that I have come across several different machines that simply needed restrictors on both ends to work properly.

The restrictor at the rod end only just did not do the trick. Put them at both ends and the problem was solved.

Why, I have no idea,:confused3: I just know that restrictors at each end has taken care of the problem in several different cases and has never caused a problem that I know of.

This is why I recommend (a set of flow restrictors) with any top or tilt units that I quote. Again, to the best of my knowledge, none of my units have had this problem when flow restrictors are installed at each port.

I can only comment on how things have actually worked for myself and my customers. When there are other unknown factors at play, people should either trouble shoot in a methodical way or just live with the problem.

Sort of has to be one or the other.

As far as the pump having to keep up against gravity with the restrictors at each end, because of the restrictors and the slowed flow that they provide, the pump has no problem keeping up with the fluid flow.

 

[npalen]

I guess it boils down to the pressure differential between the pump output and the rod end of the cylinder given the two restrictors and a heavy load on the rod end. Lets assume that the pressure differential is hypothetically zero. The volume of fluid exiting the rod end of the cylinder is less, because of the bore/rod differential, than the fluid that has to fill the base end to prevent a vacuum. So the pump is having to force more fluid thru an orifice of the same size as the one restricting a lesser flow rate at the rod end. Saying that the pump "can't keep up" is probably confusing the issue because it can keep up the volume but it can't force more fluid into the base end than what is coming out of the rod end. (Depending on the load on the rod end of course)

Edit: Case in point would be a heavy "bush hog" putting a lot of cantilevered load on a small bore top cylinder. The rod area of this already "small" cylinder increases the pressure in the rod end even more.
When lowering the "tail end" of the bush hog by extending the cylinder the pump is being asked to replace a larger volume of fluid thru the same orifice size that is restricting a lesser volume of fluid at the rod end
Not trying to be obnoxious here but rather trying to wrap my brain around what might happen on some tractors with heavy 3PH implements.