Can I plumb spool valve sets in series?

[NormL]

I posed this question in Built it forum where I have been posting the progress on my mini back hoe. No-one has come forward with any advice and I'm needing some to keep safe. Here's the question: Is it possible to plumb a 4-spool, 2-spool, and single spool - all of them open center - together in series? I need to valve seven cylinders in total and was only able to afford to buy a 4-spool set. A neighboring farmer gave me a 2-spool set he had never used and I had the single spooler from a bale loader I am using for some of the components. The 4 and 2-spoolers are made to accept 1/2" plumbing and the single takes3/8". The pump I'm using is off the bale-loader already mentioned. I have only a basic understanding of hydraulics and must plead ignorance of a good deal of the do's and dont's involved. I'm hoping someone on this site can give me some guidance...

 

[J_J]

Yes, you can plumb open center valves in series.

There is however a problem if the valve does not have a PB port.

Most valves have a 500 psi limit for back pressure on the OUT port, and may damage the seals in the valve if pressure is higher.

 

[BukitCase]

Simple answer - only if all but the LAST valve in the series string have a Power Beyond option - most, if not all, hyd. valves will NOT take full system pressure on their OUTLET ports - it will usually blow the seals and make big messes, etc.

If TWO of your three valve banks have PB ports, you could run from pump to first valve, PB out to second valve, PB out of #2 to third valve, TANK out of third (last) to return to tank.

Tank outlets of first two valves would get teed into tank outlet of last, NON-PB valve, and that one common tank return line goes back to the tank.

Any inline filter would typically go just before the tank itself.

The valve section closest to pump would take priority, so if you move a lever on that first valve (and it can use ALL the pump's output) nothing beyond that will work simultaneously.

When I say "closer to pump", I mean flow-wise, NOT physical location.

It would help if you have brand/part #'s and pix of the valves you have, maybe someone will see something they recognize (like a PB port, or lack of it) ...Steve

(JJ posted while I was typing this - guess ya gotta be quick :=)

 

[NormL]

Thanks for replying, gentlemen! I appreciate all the helpful advice I can get. The post I did on Build it yourself has pix on it. I'll try a link to it here and maybe that will help with the PB question. http://www.tractorbynet.com/forums/...s-time-either-get-started-15.html#post3400963

 

[NormL]

Here is the 4-spooler that I have. It is supposed to have PB and the return pressure limit is 1100 lb. As a working pressure that seems a little low. Thoughts? BM40 4-Spool Directional Control Valve | Princess Auto

 

[J_J]

No, not really, as most return/OUT ports are about 500 psi.

That valve will handle just about anything you can flow through it.

Any return port expended fluid will normally goes to tank.

What is the relief valve pressure on your machine?

The high pressure fluid will flow through the valve and exit the PB port.

You will probably never see the 1100 psi return port pressure unless you restrict the return lines, or make the mistake of using the OUT flow for a downstream valve.

 

[NormL]

[What is the relief valve pressure on your machine?]

I don't know that yet. It's a Cessna and before I installed it, I ran the numbers on Google. Nothing came up for some reason so I only know it was what was used to operate the hydraulics of a New Holland bale loader. I will be installing a gauge before I try using it.

[You will probably never see the 1100 psi return port pressure unless you restrict the return lines, or make the mistake of using the OUT flow for a downstream valve.]

That is what I meant with 1100 lb being a low "operating pressure". I could expect seal failure before I got much, if any, digging done? Now I need education in how PB works and how I plumb the 4-spooler for it.

 

[J_J]

PB port with an adapter is the port used to pass fluid downstream to the next valve. It is necessary to maintain hyd system integrity. Each port the pump flows through needs to be able to handle high pressure.

So when you are connecting valves in series, you connect the pump to the IN port of the first valve , and the PB port of that valve is connected to the IN port of the next valve., and so on.

The last valve does not need a PB port as the low pressure is just going to tank.

 

[NormL]

PB port with an adapter is the port used to pass fluid downstream to the next valve. It is necessary to maintain hyd system integrity. Each port the pump flows through needs to be able to handle high pressure.

So when you are connecting valves in series, you connect the pump to the IN port of the first valve , and the PB port of that valve is connected to the IN port of the next valve., and so on.

The last valve does not need a PB port as the low pressure is just going to tank.

Looks like there is more to it than just running a hose or hard line from whichever is the PB port? There is little to go by for labeling on that valve body. I bought it off the shelf and neglected to ask for a spec/diagram sheet. When I go back there to stock up on the fittings I need to run the lines from, I will have to get the rest of the information I should have gotten when I made the purchase! The letters P and B are cast near one of the ports - not close together like PB. More like P---B, on either side and under the port opening.

 

[J_J]

The PB port is on the side under the tank port.

The inlet side is facing you and you see the relief valve.

Everything you every wanted to know about the BM40 valve.

https://www.google.com/url?sa=t&rct...=CTbaR5BB3nuD7u6gIkwFmg&bvm=bv.49784469,d.eWU

Page 30 will show the carry over plug CO plug = PB adapter.