determination of inlet- outlet on an unmarked closed center valve body

bemodoc · Mar 30, 2014

Hi. everyone new to the forums.I have read a lot of the forums on the differences between open center and closed center hydraulic systems which were very informative but leaving me needing to know more about the internal workings of the closed center systems.I have a JD 401b industrial tractor that did have a front 6 way dozer blade and a rear compactor wheel on it.I removed these and adapted an international 3514 fel to it and adapted a JD E-9250 backhoe to it.The 3514 was an open center system,changed the fel control valve over to a JD closed center off of the 6 way dozer.The JD E-9250 backhoe has the closed center valve already.My question is the valve body on the 9250 is not marked inlet-outlet or any other letters,numbers,etc and the port openings are the same size.How would you determine the high pressure port and the return port,also how and when does the oil return to the tank ? As in the example as raising then lowering the bucket or curling and dumping the bucket.I am at point of plumbing the hoe and do not want to blow any thing up.I have applied air to all of the hoses, 90% of the time the air seems come out of one port the 2nd port only once had very noticeable air.The air was applied from the distribution block backwards with the valve held open,checked in both directions with one hose disconnected at a time.I actually spent over 2.5 hours at a John Deere dealership with one of their mechanics going through old manuals,microfiche files,computer and cd roms and could not come up with anything conclusive.We kind of both come to wonder if it made any difference with either port as to inlet-outlet.But I need to know positively,there seems to me there should be a standard rule of thumb for determing this but who knows in hydraulics.I know one thing I am glad the John Deere mechanic didn't charge me mechanics wages for all the time he spent.I know this is long for a newbie and I apologize, if you gentlemen can help me I would be very appreciative.Thank you.

J_J · Mar 30, 2014

In a closed center hyd system, no fluid flows through the valve in neutral.

The ports used are IN port OUT port, work ports.

The pump may have a standby pressure, and this pressure is waiting at the IN port of each valve , which are in parallel, waiting for something to happen.

When you activate a closed center valve, fluid is directed to the cyl or motor, and the out flow from the motor or cyl will pass through the OUT port.

Some valves are convertible, where you take an open center valve and closed off the PB port. This will make that valve a closed center valve.

Most valves are marked in some way.

bemodoc · Mar 30, 2014

Thank you for the quick reply.I understand that but does it make a difference which port I hook up my high pressure line up to.This 401b does have the accumulator system with the closed center pump.I bought this 9250 hoe that had been off the machine for a while and the machine is gone so I didn't see how it was hooked up.

J_J · Mar 30, 2014

Does the valve have a relief valve on it, and if so, the relief is normally located close to the IN port.

So in order to test a closed center valve, you use and adapter air hose fitting and pressurize the valve.

In neutral, no flow.

Push the lever fwd, air will flow out a work port, and pull the lever back, and air will flow from the other work port.

If you put the air in the tank ports, and pull or push the lever, air will flow from a work port.

Show picture of valve.

bemodoc · Mar 30, 2014

Sorry.JJ I am new to this I replied to the thread instead of the reply at the bottom your answer.thank you

bemodoc · Mar 30, 2014

I thought about making an adapter and suppling steady air pressure to the valve body,i will have to do that.I just checked for a relief valve don't see one.I will take a picture right now and try to figure how to down load it.

J_J · Mar 30, 2014

A lot of closed center valves do not have a relief valve . The system relief is located in the pump area.

Convertible hyd valves might have a relief valve but does not need one.

bemodoc · Mar 30, 2014

I am going to try to load these pictures now.The first valve body section to the left of the picture is the inlet-outlet section the upper one is painted the lower is unpainted. The rear pictures show the two ports, hoses