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Help on 3 point hydraulics (an update)

stevieb49829

stevieb49829

Well-known Member
Location
Spirit Lake, Idaho
Back in October, I got help from folks on my loader hydraulics power beyond capabilities. I took the advice and added the plug that converted my loader valve to power beyond, and now my 3 point works like it should. However, the plug was advertised as converting my valve to closed center. After some heavy duty thinking, it made sense. The plug plugs off normal return to tank. At that point the flow is stopped and can go nowhere, but in my case, it now follows the hose off the BYD port, straight to my second valve that runs the 3 point. But it begs the question: where does the flow go on a closed center system? Thanks again, and again, and again for all your knowledge and help. steve
 
The open or closed flow system depends on the type of pump.

An open flow system is used with a positive displacement pump, a gear pump. A pump that always moves oil and must return the flow to the tank.

A closed system uses a variable displacement pump, a vane pump or swash plate pump. The pump senses and maintains pressure. When the pressure drops, as in demand, the volume increases to maintain the needed pressure. When the demand drops, the pump volume drops so it is not building heat or robbing power.
 
A properly plumbed power beyond sleeve (as yours apparently is) blocks off the normal return to tank passages from the center (or pressure supply) passages. The return to tank port is still there, and still in use. When the valve is actually in use (like when operating the loader) the oil flowing out and back into the work ports is directed through those passages and back to tank so to speak. It's also in play when the loader relief valve opens providing that low pressure relief flow a free flowing path back to tank.

Often the sleeve is referred to as a closed center adapter because if you install a plug into the port instead of a fitting and a line leading to another valve, then the valve can actually be used on a closed center system. In that case no fluid ever exits that fitting. The tank return port is still used, but only for oil returning through the work ports.

If you read through this material it may help give you a sense of why you're better off with a functioning power beyond sleeve in your valve than you were without one.

https://crossmfg.com/parts/valves/ba-bc-series-valves/power-beyond-option
 
No, I think you're mistaken on the call. I didn't call anyone. That must have been someone else. Since you haven't explained what tractor you have or what the original issue was, I won't comment on whatever the fix turned out to be. Only that if it works, it must be right. That's true in MOST cases.

Adding or changing hydraulic valves and attachments can be as simple or as complicated as you make it. It can be pretty simple once you understand a few basic concepts. I deal with this sort of thing on a regular basis so most of it now it takes no thought at all. If you have any more questions you can reply here or to my Email. I will try to explain whatever I can.
 

I think your a bit confused on how power beyond works
You can not have power beyond flow and closed center on a valve at the same time

A open center flows fluid from the main supply passage and return ports into a common return port

Notice the plug does not extend into the open center passage
mvphoto111306.jpg


Closed center completely blocks flow from the open center passage and only allows return flow to exit the end outlet
This plug converts the valve from open center to cooled center
This conversation should not be done on older tractors with gear pumps

Notice the plug extends into the main passage completely blocking flow
mvphoto111307.jpg


Power beyond sleeve divides the flow between the main passage and the return ports
This allows fluid to continue to flow beyond this valve to another device such as your 3 point lift, fluid from the return ports flows through the end outlet back to the tank or tractors sump

mvphoto111308.jpg
 
Thanks, Destroked. I do understand the difference. In your second diagram, the plug they used is the one I needed to use my power beyond. That's what was throwing me. But after a couple of discussions with Harry, at Cross Mfg, they convinced me it is the way this 2 spool is designed. What isn't shown in the second diagram is a port directly below the head of the ''open center passage'' arrow, with a plug in it, and ''BYD'' stamped next to it on the outside of the valve. I plumbed my second valve to this port, and inserted the required ''closed center conversion plug''. I do understand that I could have used a power beyond sleeve, as shown in your 3rd diagram, but that would have run the flow out the side of the valve, instead of out the top with all the other ports. My valve is a SDV series 2 spool, not the BA and BC series these diagrams were designed for. Thanks for the good info. It may help others understand the differences between closed and open centers. steve
 

I see with your modified drawing the closed center conversion plug is used to redirect flow through the extra port your valve has
So even though it has a closed center plug it still acts as a open center system with power beyond
If you plug that port you have a closed center valve
 
I think Cross designed this valve, and the available plugs to be as versatile as possible. The problem was they had no drawings that showed the use of what they were calling a closed center plug to send flow to the BYD port. Maybe I should copywrite my modification of their drawing, eh?
 
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