# Analysis and troubleshooting of Manifold block hydraulic directional valve and electro-hydraulic directional valve

The electro-hydraulic directional valve and the hydraulic directional valve are mainly used in the hydraulic system where the flow exceeds the normal working range of the electromagnetic directional valve to control the action of the actuator or the flow direction of the oil. Previously, we talked about “Detailed Structural Explanation of hydraulic directional Change Valve” and “Detailed Structural Explanation of Electro-hydraulic directional change Valve”. Today, we will talk about fault analysis and elimination of hydraulic directional change valve and electro-hydraulic directional change valve.

The difference between the hydraulic directional valve and the electromagnetic directional valve lies in the difference of the force that pushes the spool to move. The former is the hydraulic pressure of the pressure oil, and the latter is the suction force of the electromagnet. The specific fault analysis and troubleshooting methods of the hydraulic directional valve are as follows.

Failure of hydraulic reversing valve :(1) no reversing or bad reversing

Reason: the control pressure oil pressure that pushes the spool to move is not enough, or the control oil pressure is enough, but the oil return of the other end of the spool control oil cavity is not smooth, the reason for not smooth may be dirt blocking, or the opening volume is not large enough, or the oil return pressure is large. All of these conditions cause the spool of the hydraulic reversing valve to be unable to move or move flexibly, which can not be reversed or produce bad reversing.

The solution:

1. Properly increase the pressure of the control oil. The control oil pressure range of the 6.3mpa series hydraulic directional valve is 0.3-6.3mpa, and the control oil pressure range of the 32mpa series valve is 1-32mpa, and it is impossible to reverse the hydraulic valve when it is lower than the lowest value.

2. The middle position in the unloading state of M, H, K and other hydraulic reversing valve, if the control oil is taken from the system, it must be installed on the oil return road a back valve, and the back adjustment value should be large enough to friends enough pressure control oil to make the raft core movement reversing.

3. If the return spring is broken and cannot be reversed, the return spring must be replaced.

4. When disassembling and repairing, the valve cover direction is incorrectly installed, which will lead to no oil intake or oil return of the control oil, resulting in no reversing. At this time, the assembly direction of the valve cover should be corrected, and the control oil port on the valve cover should be directly opposite the control oil port on the end face of the valve body: for the control oil introduced from the top cover plate, the direction of the cover plate should also be paid attention to.

Failure of hydraulic reversing valve :(2) large reversing vibration and reversing impact exist

Cause: the reversing impact occurs when the oil port pressure changes sharply during the reversing, and the general valve core reversing speed is too fast at this time.

Solution: in order to make the pressure change slowly, it is necessary to try to make the spool reversing speed slow, can be in series on the control oil circuit at both ends of the valve small adjustable one-way throttle valve: or take the shoulder of the reversing spool platform design or processing into a cone surface or open triangular throttling groove and other measures, impact problems can be solved.

Common failure reasons and elimination countermeasures of electro-hydraulic directional valve

Fault symptom Cause analysis and elimination measures

The main

valve

heart

Don’t

shipment

Electromagnet fault electromagnet coil burned out check the cause, repair or replace

Electromagnet driving force is insufficient or magnetic leakage inspection reason, repair or replace

Electrical circuit fault elimination fault

The control signal is not added to the electromagnet after checking the control signal

Electromagnet core stuck maintenance or replacement

Pilot solenoid valve failure valve core and valve body hole stuck (such as parts of poor geometric accuracy, valve core and valve hole with too tight; (the oil is too dirty) repair with clearance to meet the requirements, so that the valve core is flexible; Filter or replace the oil

The spring is bent and the slide valve is stuck. Replace the spring

Main valve center stuck valve center and body hole geometric accuracy difference repair and research clearance to meet the requirements

The valve core and valve hole match is too tight to repair and research clearance to meet the requirements

There is something wrong with the surface of the valve core, remove the burr and rinse it clean

Hydraulic control system fault control oil circuit no oil

(1) The control oil solenoid valve is not reversed

(2) the control oil circuit is blocked (1) check the cause and eliminate

(2) Check the cleaning, and make the control oil pipeline unobstructed

Control oil pipeline pressure is insufficient

(1) The valve end cover leaks oil

(2) The throttle valve at one end of the oil discharge chamber of the slide valve is adjusted too small or blocked (1) Tighten the end cover screw

(2) Clean the throttle valve and adjust it appropriately

Oil change the oil is too dirty to make the valve core stuck filter or replace the oil

The oil temperature is too high, so that the parts produce thermal deformation, the phenomenon of stuck check the oil temperature is too high cause and eliminate

The oil temperature is too high, the oil produces colloid, stick to the valve core surface and stuck to clean, eliminate high temperature

The oil viscosity is too high to make the valve core difficult to move and stuck to replace the appropriate oil

Poor installation deformation of valve body

Install screws tighten the screws if the torque is not uniform. Tighten the screws so that the force on the screws is uniform

The pipe installed on the body is reinstalled “gently”

The return spring does not meet the requirements of the spring force is too large to replace the appropriate spring

Spring bending, deformation, resulting in the valve core stuck

A broken spring cannot be restored

Insufficient flow through the valve center after reversing

The push rod in the solenoid valve is too short to replace the suitable length of the push rod

The geometric accuracy of valve core and valve body is poor, the clearance is too small, and the phenomenon of stuck when moving is not in place to meet the requirements

The spring is too soft, the thrust is insufficient, so that the valve core stroke can not hit the terminal to replace the spring suitable for elasticity

Excessive pressure drop insufficient choice of parameters the actual flow is greater than the rated flow should be used in the rated range

Hydraulic control valve heart reversing speed is not easy to adjust adjustable device failure one-way valve sealing poor repair or replacement

Throttle valve processing precision is poor, the minimum flow to replace the throttle valve

Oil leakage at the valve cover of the oil discharge chamber Replace the seal and tighten the screw

Conical throttle valve regulating performance is poor to use triangular groove throttle valve

Electromagnet overheating or coil burned electromagnet fault coil insulation is not good replacement

Electromagnet heart is not suitable to be replaced

Low or unstable voltage conversion value should be within 10% of rated voltage

Electrode weld is not good re-weld

Load change reversing pressure exceeds prescribed reduction pressure

If the reversing flow exceeds the specified, replace the suitable electro-hydraulic reversing valve

The oil return port back pressure is too high adjust the back pressure to make it within the specified value

Defective assembly of electromagnet core and valve core axis of coaxiality poor assembly, to ensure good coaxiality

The electromagnet suction is not enough, the assembly is not good, the push rod is too long, repair the push rod to the appropriate length

Electromagnet core contact surface is uneven or bad contact to eliminate dirt, re – assembly

Impact residual vibration reversing impact large-diameter reversing valve, due to the large size of electromagnet, fast suction speed and impact need to use large-diameter reversing valve, electro-hydraulic reversing valve should be selected

Hydraulic directional valve, because the control flow is too large, the movement speed of the valve core is too fast, and the impact is generated by reducing the throttle valve and slowing down the movement speed of the valve core

The one-way valve ball in the one-way throttle valve is missing or broken, causing no damping effect to repair the one-way throttle valve

The screw that vibrates to fix the electromagnet loosens the fastening screw and adds the anti-loosening washer