Check valve question

[Oldstuff]

I am about to buy a cylinder to add to the rear of my L3400 for my top link, I am looking at other posts here on this site and see some add a check valve and others do not. I use my tractor with a rotary cutter mainly but also have a 7-shank cultivator for putting in my food plot and a rear blade for a little bit of rear blade works on a gravel lane. My ground is pretty level with just a few gradual up and down areas, the lane I blade sometimes is not as level.

I cannot understand why I would need/want a check valve in this top link system, I am mowing, blading and cultivating now with no problems and am using the basic 3 pt lift as the tractor was originally made.

Can you guys explain why I do or do not want a check valve in this system?

 

[K5lwq]

If the rear remote valve leaks internally a check valve will keep it from moving once you have it set. You do lose the ability to put the cylinder into float mode with the check valve.

Most people will put checks on the side link and not the top link. Others don’t use checks at all. It depends on your preference.

 

[Oldstuff]

Thanks K5, that is what I was thinking but wanted to hear another opinion.

Oldstuff

 

[skipmarcy]

If you're using a ground-engaging implement such as boxblade, various plows etc., minor changes in the toplink angle/length will have great effect on how the equipment performs. Very minor changes in the toplink when boxblading make huge differences - once you find the sweet spot you want to keep it - a pilot operated check valve does just that. I've had one on my toplink cylinder for 20 years now. The only time I ever want "float" in my toplink is with my bushog and that is built-in on my Howse with the slotted frame that the toplink pin goes thru on the equipment.

 

[LD1]

IT seems that no matter what I am doing (plowing, cultivating, blading, etc) I am constantly adjusting the toplink on the fly to get desired results. Not because it moves or leaks down or anything. But because The ground is constantly changing and I am adjusting based on load and results of the implement.

I have never needed the toplink to stay stationary for more than 5-10 min at a time. Therefore a check valve would do me no good

 

[ericm979]

My hydraulic top link can move in or out a bit when there is force on it, like when pulling with a forestry winch or box blade. I cycle it in and out pretty often as I need to tilt my implements back all the way to get the tractor in and out of the barn to clear the ramp. This means it gets retracted all the way and then extended back out at least a couple times every time I run the tractor. That should purge air from it right? I have tried purging the cylinder by running it in and out a few times with nothing on it. It seems to move less under force when I do that but it still moves.

Would a pilot valve kit fix this? I have no need of float as my valves do not have a float position and my rotary cutter has its own float built in.

 

[K5lwq]

My hydraulic top link can move in or out a bit when there is force on it, like when pulling with a forestry winch or box blade. I cycle it in and out pretty often as I need to tilt my implements back all the way to get the tractor in and out of the barn to clear the ramp. This means it gets retracted all the way and then extended back out at least a couple times every time I run the tractor. That should purge air from it right? I have tried purging the cylinder by running it in and out a few times with nothing on it. It seems to move less under force when I do that but it still moves.

Would a pilot valve kit fix this? I have no need of float as my valves do not have a float position and my rotary cutter has its own float built in.

Yes a pilot operated check valve will work for you. But the air needs to be out of the system or it still can move some. I would find out why air is getting in and correct that as well as adding a check valve.

 

[BufordBoone]

I have addressed the leak-down issue two ways.

Check Valve - lose the ability to put the cylinder in float. Easy to make on the fly adjustments without worry about leaking down. This is on a 10' offset cutter. It is way heavy on the right side. Without the check valve I'd have to adjust the cylinder about every 10 minutes of cutting.

Ball Valve - Keep the ability to put the cylinder in float but have to open the valve to adjust.

The Ball Valve is my preference for most operations. If not for the offset cutter, I'd have the ball valve on both tractors. I got it from Fit Right. He also offers (I think) and electric version that you could wire in and switch on or off.

The check valve is installed on the cylinder. The Ball Valve is installed at the hydraulic coupling site.

I setup my Ball Valve so that I can install or remove it easily. Male adaptor on one side, female on the other. Want to use it, plug it in. Want to move to other remote, easy to do.

 

[ericm979]

Yes a pilot operated check valve will work for you. But the air needs to be out of the system or it still can move some. I would find out why air is getting in and correct that as well as adding a check valve.

I'm trying to think how air would get in. I don't think it's coming from the tractor's hydraulic system or I'd be seeing effects with other cylinders. To get air into the top link cylinder it would need to be under vacuum at some point even if transitory. When the implement is raised in the air, the weight is trying to pull the rod out of the cylinder. So when its static there is pressure on the rode side and suction on the cylinder side. Which means that if the cylinder fittings or hoses or quick connects can allow air in, then it would get into the cylinder side.

I don't see a mechanisim for getting air into the rod side though, as gravity should ensure sure that it's always under pressure that is higher than atmospheric. But the behaviour I see would indicate there is air there. Or maybe the valve is letting fluid past under pressure.

I'm probably missing something. Also is there a way for this to happen without air in the cylinder?

 

[K5lwq]

The valve leaking internally is most definitely a possibility. All valves leak to a degree and some more than others. The check valve will fix that for sure. Maybe you don’t have air at all it just seems that way. I would try the check valve and go from there. One day I will add a hydraulic top link to my Branson and I definitely use check valves as that valve leaks pretty bad.