4 Common faults of WEH16 electro-hydraulic reversing valve

Common faults and analysis of 4WEH16 electro-hydraulic reversing valve are as follows:

Reversing is unreliable or cannot be reversed

Fault manifestation: The system pressure suddenly drops to a low pressure state (such as 0.3MPa) during reversal. The pressure recovers after restarting, but the fault recurs when reversing again.

Reason analysis:

Electromagnet failure: The electromagnet is damaged or the wire is disconnected, resulting in the inability to push the valve core to move.

The reset spring force of the pilot valve or main valve is insufficient: the spring is aged or broken and cannot reset the valve core.

The valve core is stuck: The main valve core or the pilot valve core is stuck due to roughening, dirt blockage, poor processing accuracy and other reasons, and cannot move.

Transition function problem: The main valve core stroke is too long (such as 20mm), and it needs to go through the neutral transition function during reversal. If the control oil pressure is insufficient, the pressure difference between the two ends of the main valve core is small, resulting in unreliable reversal.

Problems with the control oil circuit: The control oil pressure is too low or the flow rate is insufficient to push the valve core to move; the control oil circuit leaks, resulting in pressure loss.

Solution:

Check the electromagnet and wires, and replace damaged parts.

Replace the return spring and ensure that the spring force meets the requirements.

Clean the valve core, repair or replace the valve body and valve core with poor processing accuracy.

Install a pre-control pressure valve (such as a plane seal check valve) in the P cavity of the main valve to increase the pressure difference between the two ends of the main valve core.

Adjust the control oil pressure and repair the leakage point.

Abnormal system pressure

Symptoms of failure: The system pressure cannot be established or the pressure fluctuates greatly.

Reason analysis:

Oil contamination: Dirt in the oil blocks the sliding gap of the throttle valve or valve core, causing the reversing valve to become stuck or the oil return to be blocked.

Oil return back pressure is too high: The oil return filter element is clogged or the oil return pipeline design is unreasonable, resulting in increased oil return resistance and affecting system pressure.

The oil viscosity is inappropriate: the oil viscosity is too high and the valve core moves inflexibly; the oil viscosity is too small, resulting in increased internal leakage.

Solution:

Replace the clean oil, clean or replace the throttle valve and filter element.

Check the oil return pipeline, clean or replace the clogged filter element, and optimize the oil return design.

Choose an oil of appropriate viscosity based on system requirements.

The electromagnet is overheated or the coil is burned out

Fault manifestation: The solenoid temperature is too high or the coil is burnt, causing the solenoid valve to have no action.

Reason analysis:

Unstable voltage: The coil is under-voltage or over-voltage, resulting in insufficient suction or overheating of the electromagnet.

Coil quality problems: The coil insulation is damaged or the turns are short-circuited, resulting in burnout.

The residual magnetism of the electromagnet is large: The residual magnetism of the DC electromagnet is too large, causing the valve core to not reset.

Solution:

Use a multimeter to check the coil voltage to ensure that the voltage is stable and meets the requirements.

Replace the coil with qualified quality and repair the damaged parts of the insulation.

Choose a DC electromagnet with small residual magnetism or take degaussing measures.

Valve body leakage

Failure manifestation: Serious external or internal leakage of the valve body, resulting in a drop in system pressure or a waste of oil.

Reason analysis:

Damaged seals: O-rings, gaskets and other seals are aged or damaged, causing leakage.

Poor machining accuracy of the valve body or valve core: the fitting gap between the valve body hole and the valve core is large, resulting in increased internal leakage.

Improper installation: The roughness or flatness of the valve body installation surface does not meet the requirements, resulting in loose sealing.

Solution:

Replace damaged seals to ensure reliable sealing.

Rearrange the valve core to ensure that the clearance between the valve body hole and the valve core is reasonable.

Repair or replace valve bodies and valve cores with poor processing accuracy to ensure that the roughness and flatness of the installation surface meet the requirements.

Slow start of direction change

Fault manifestation: The working parts start slowly when changing direction, and the movement speed is slower than the normal speed.

Reason analysis:

The opening of the throttle valve is too small: The opening of the throttle valve that controls the movement speed of the reversing valve spool is too small, causing the spool to move slowly.

Insufficient suction force of the electromagnet: insufficient thrust of the electromagnet and insufficient movement force to push the valve core.

Insufficient control oil pressure and flow: Insufficient control oil pressure or flow causes the reversing valve core to move slowly.

The valve core is not flexible in movement: The valve core is not flexible in movement due to lint, dirt, etc.

Solution:

Appropriately increase the opening of the throttle valve and increase the movement speed of the valve core.

Repair or replace the electromagnet to ensure adequate suction.

Check the control oil circuit to find out the reasons for insufficient pressure and flow and eliminate them.

Clean or repair the valve core to ensure flexible movement.