Cetop Valve Not Changing Motor Direction

[CD_UK]

Very simple circuit - Cetop 3 valve on a single manifold with PRV, feeding a reversible gear motor.
Whichever solenoid is activated, the motor turns in the same direction.

If I swap the hoses over, the motor does change direction, (although the valve still does not reverse the flow when the opposite coil is activated).

I have tried a replacement valve (of different brand) and I get the same result.
(A hydraulic supplier, clutching at straws, suggested perhaps I may have received a valve that was mislabelled, but after replacing it and getting the same results, I'm ruling this out now as the cause)

Cetop valve is 3-position, all ports open in neutral position.

Any ideas?

 

[zeusfaber]

What sort of valve is it? "CETOP 3" tells you where to find the ports on the soleplate, but not what is meant to happen inside the valve.

Assume you've already confirmed positively that you are activating the solenoids you think you are.

A.

 

[hydtools]

DC coil polarity?

Ted

 

[FluidPowerUser]

DC Coils don’t have polarity in general. Unless they are marked with +/-, they can be connected either way.

Check the connections to the block. If the pressure is connected to the T port, the motor will turn in whichever direction has the highest force acting on it.

 

[73lafuite]

Hello,
Your story seems impossible. When you have found the solution to the problem I will have learned a little more.
Just an idea: the motor should have a 3rd drain port. Otherwise it must have 2 check valves inside which evacuate internal leaks towards the orifice which has the lowest pressure.
Do you have the same torque on the motor in both directions of rotation? Or in one of the two directions it does not provide torque so if it is blocked the pressure does not rise?
Cordially

 

[CD_UK]

Thanks very much for the replies.

Coils are DC, and operating correctly. Manually overriding them achieves the same result, so it's not a coil issue. The coil plugs have led indicators, and are receiving power independently, (i.e. both are not accidentally being powered simultaneously).

Pressure and tank lines are correctly plumbed in as per the P and T indications on the manifold.

The motor does indeed have a 3rd (case drain) port, which goes directly to tank.

The motor spins a flail rotor, and requires the same torque whichever direction.

 

[73lafuite]

I would disassemble the distributor from its base plate. And I would puff with a cigarette or compressed air while operating the spool. If air always exits from the same side then the spool in the valve is an asymmetrical 4/2 valve spool.
Normally with a completely open center the springs, pushers, centering washers are identical on both sides. And the spool is symmetrical with respect to its center.

 

[CD_UK]

Thanks. I'll give that a try when I'm in the workshop.

Still very odd how two valves (of different brands even more so), are behaving this way. Will be very coincidental if I find the incorrect spool has been installed in both.

 

[73lafuite]

Hello,
Also check with the manual pushers and or by disconnecting the Hirschmann plugs that the correct coil is powered and that there are never 2 coils powered at the same time.
I always told my automation engineers that they were less reliable than hydraulic engineers...