Common Directional Control Valve Failures and the Solutions

Figure 1: Eaton DG series directional control valves of different models.

In the process of using the directional control valve, various failures may occur in the slide valve, electromagnet, and reversing valve. For different failures, the solutions are also different. Here are four types of common failures and the solutions.

1. The Slide Valve is Stuck

(1) The fitting clearance between the slide valve and the valve body is too small, and the spool in the hole cannot move or cannot properly move:
Check the clearance, or replace the spool.
(2) The spool is damaged and the oil is polluted:
Check, repair the mold or reconfigure the spool, and change the oil.
(3) The geometry of the spool is unqualified; the assembly of the spool and the valve hole is not concentric, giving rise to axial hydraulic jamming:
Check, correct the deviation and coaxiality, and check the hydraulic jam.

Figure 2: Seat hydraulic directional control valve SEC 6.

2. Failures in Oil Circuit

(1) The oil control pressure is not enough. The slide valve does not move, and cannot reverse or cannot properly reverse:
Increase the control pressure, check whether the spring is too hard, and replace it if necessary.
(2) The throttle valve is closed or blocked:
Check and clean the orifice.
(3) The oil drain ports at both ends of the slide valve are not connected to the oil tank or the oil drain pipe is blocked:
Check and connect the drain pipe back to the tank. Clean the oil return pipe to make it unobstructed.

3. Failures in Electromagnet

(1) The AC electromagnet was burnt because the slide valve was stuck and the iron core could not be sucked to the bottom:
Clear the jamming fault of the slide valve and replace the electric iron.
(2) Magnetic flux leakage and insufficient suction:
Check the cause of magnetic flux leakage and replace the electromagnet.
(3) Poor welding of the electromagnet wiring and contact:
Check and re-solder.

4. Solenoid Valve cannot Reverse

Figure 3: Different types of ICS directional control valves.

(1) The spring is broken, missing, or too soft to restore the slide valve to the neutral position, so that it cannot reverse:
Check, replace or refill springs.
(2) If the voltage is too low, the electromagnet cannot be pulled in:
Correct the voltage.
(3) The screw for installing the valve is too tight, and the inner hole of the valve body is deformed, preventing the spool from moving:
Adjust the tightening torque of the screws to the manufacturer's recommendations.
(4) The hydraulic oil is polluted and the gap is uneven. The pressure distribution in the circumferential direction of the spool is different, and the static friction force on the side with the smaller clearance increases. Therefore, the action of the spool is inflexible, and the spring cannot operate normally, so that the spool cannot reverse:
Clear the channel.
(5) The length of the push rod of the electromagnetic reversing valve is not enough after wear, so that the spool moves too little or too much, causing the reversing to be ineffective:
Check and repair, and replace the push rod if necessary.

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