hydraulic diagram & plumbing

[Cord]

First Question: Does anybody know where I can find the graphic spool diagram for a standard 4-way valve? I'm looking at a solenoid valve and I'm not certain that it's the correct function for what I want it to do.

Second question: Can two open center valves be installed in the same circuit? Do they need to be in series or can I installed a T in the supply line? The valves don't need to function at the same time.

 

[RonMar]

1. Try the Prince Hydraulics site. They have some pretty good diagrams.

2. In theory you could have an infinite number of open center valves but they must be in SERIES. An open center valve is just as it's name implies. The inlet port is a direct path to the outlet port. Untill one of the spools diverts flow to a working port, the fluid flows through the valve body relatively unobstructed(all flow, no pressure) so there is no load on the engine powering the system. If you put two valves on a "T", as you try to get work out of one of the valves, nothing will happen as the fluid will just bypass the work through the open center of the other valve.

With 2 valves in series, there will be no alternate path so as you operate one of the spools, there will be no other path but to the cylinder/motor and pressure will build and work will be performed(and a load will be placed on the pump and engine). You will however only really be able to get any work out of one spool at a time. In a system with double acting cylinders or motors, the flow is never really interrupted. As you divert fluid from the inlet port to a cylinder or motor working port, the return from that cylinder or motor is sent to the valve outlet. This fluid heading down stream from the valve being operated could be diverted by another valve. But as the second cylinder or valve starts to perform work(fluid pressure builds), it will put backpressure on the return side of the first cylinder and hydraulically increase the weight it is moving. The first cylinder would move slower and in turn feed fluid from it's return slower causing the second cylinder to also slow down.

 

[MadReferee]

</font><font color="blue" class="small">( You will however only really be able to get any work out of one spool at a time. In a system with double acting cylinders or motors, the flow is never really interrupted. As you divert fluid from the inlet port to a cylinder or motor working port, the return from that cylinder or motor is sent to the valve outlet. This fluid heading down stream from the valve being operated could be diverted by another valve. But as the second cylinder or valve starts to perform work(fluid pressure builds), it will put backpressure on the return side of the first cylinder and hydraulically increase the weight it is moving. The first cylinder would move slower and in turn feed fluid from it's return slower causing the second cylinder to also slow down. )</font>

Close, but not quite right. You missed the whole idea behind a power beyond valve setup.

Assuming 2 open center valves in series, the first one will almost always have power beyond. The fluid exhausting from the cylinder will go to the return to tank outlet not back into the main flow via the power beyond outlet. Depending on the valve design, unsued fluid by the activated spool will be available to other spools in that valve and what is still not used is dumped back into the main flow (at the power beyond outlet) to the next valve. Power beyond eliminates the problem of back pressure that you described as all exhaust fluid goes directly to the tank. Whatever flow that remains available continues on to the next valve in series.

 

[Cord]

Ok...a summary please. If I don't have powerbeyond on the up stream valve, do I connect the outlet of the up stream valve to the inlet of the down stream valve?

 

[MadReferee]

You could but it is NOT recommended. The back pressure problems could lead to more serious hydraulic failures. From my perspective, and that of most hydraulic professionals, it would be "use at your own risk".

What is your application? An aux valve for a tractor TNT? Are you tapping off the loader valve (most loader valve's have power beyond).

 

[Cord]

Well, I currently have a traditional two handle, two spool valve on my loader. The valve is a open center with out power beyond. The hole isn't even drilled (it's labled on the casting). I need to add a third spool for a grapple. Space is very tight, and I really don't have the room for a second valve. I found a solenoid valve on ebay that looks like it would work. The valve is a 4-way single spool, spring return, open center valve. I realize that buying a new valve would be the solution, but I don't have the several hundred it will cost me.

 

[RonMar]

I think what you are looking for is a hydraulic double selector valve. This valve you need has 6 ports. You would connect the two central or common ports to the working ports off of one of your existing loader valve spools such as the one used to dump/rollback the bucket. Two of the remaining ports on the selector valve would connect to the dump/rollback cylinders. The two remaining ports would connect to the grappel cylinder. This is a two position valve. In one position, the fluid will flow to/from the loader valve working ports to the dump cylinders and control the bucket like it does now and the grappel cylinder will be hydraulically locked in place. When the valve is switched, the dump cylinder is hydraulically locked in place and the flow from the loader valve then controls the grappel cylinder. You can see a manual version of one of these valves at northern tool at the following link.
http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=6970&productId=20870&R=20870

I am looking into adding a grappel circuit also but think I will go with the three spool valve with float as my current 2 spool loader valve dosn't have float(I miss having float on the lift spool for gradeing). It will also be much simpler to install.

 

[MadReferee]

Here is a 12v version of the same thing. Several here on TBN have used this valve with much success. It's from Surplus Center and priced at a few cents under $200.

Double selector valve for grapple

 

[Cord]

Thanks for the link. Most of the remote valves that I was finding were in the $400 range. I guess I was originally thinking that the grapple could be fed with a third spool, instead of splitting one of the existing spools. I could then T the line and have an accessory outlet on the tractor. Some day I'd like to build a lawn trailer with a hydraulic dump.

Here are the two valves I was looking at. I believe these would act as a standard 4-way valve:
ebay ebay

Is it just me or do all of these solenoid valves look like there are parts missing?

 

[MadReferee]

Don't let the price fool you on those eBay valves. Those valves are designed for a D03 mounting plate which you must still purchase. They are not particularly suited for your application.