Blog - Hydraulic Solenoid Valve Testing

//Hydraulic Solenoid Valve Testing

Hydraulic Solenoid Valve Testing

The hydraulic solenoid valve switches the hydraulic fluid flow direction in hydraulic systems. Usually there are several hydraulic solenoid valves mounted in hydraulic units, each valve controls different action of actuator. Some problems of slow movement, noise or less cylinder force is caused by hydraulic solenoid valve. The key to fix the problem is tested strictly before valves delivery and the manufacturer testing method. There are six steps of testing hydraulic solenoid valve as follow.  –

Hydraulic Solenoid Valve Testing Method:
1. Pressure Resistance Test
– To Pressurize 1.5times of the maximum working pressure to each oil ports at speed of 2% rate per second, holding the pressure at 5min. after approaching the testing pressure.

2. Spool Symbol Test – Solenoid Directional control valve is tested in accordance with the valve spool function, directional position and spool reset. Confirmation hydraulic flow status of each oil port. 

3. Spool Directional Function Test
Directional Test:
Adjusting the flow control valve (part no.: 2-1) and check throttle valve (part no.: 6-1 or 6-2) until the pressure on P oil port  reaching nominal pressure. Then to adjust the flow control valve (part no.: 2-2) to specified backpressure at T port, making sure the flow rate of tested valve is testing flow. 
Above these test conditions, the directional solenoid valve is energized and de-energized tested and continuous action more than once, then test the valve status of spool switching and central position. 

Pressure Holding Test:
At the above test conditions, the valve spool should be in the original position and switching position at each 5 minutes. Then, to energized and de-energized of hydraulic solenoid valve, confirm the tested valve spool switching and spool central position conditions.

4.  Pressure Loss Test – Switching the tested valve to all oil ports through and keeping the flow rate equals to testing flow rate, then checking the pressure gauge(part no.: 3-1,3-2,3-3,3-4) to measure the pressure at each point and figure out the pressure loss at A, B, P, T ports. 

Hydraulic Solenoid Valve Testing symbol

(1) Hydraulic pump

(2-1, 2-2) Pressure relief valves
(3-1, 3-2, 3-3, 3-4) Pressure gauges
(4) Directional valve tested
(5) Flowmeter
(6-1, 6-2) Flow control check valve
(7) Accumulator
(8) Throttle Valve
(9) Thermometer
(10) Check valve
(11) Fine filter
(12) General filter

For 4way and 2postion, 3position valve, when the oil flow direction is P to A, B to T, the pressure loss is known as △P(A to T)=P – A, △P(B to T)=B – T.  When the oil flow direction is P to B, A to T, the pressure loss is known as △P(P to B)=P – B, △P(A to T)=A – T.

For the 4way 3position tested valve, if the fluid flows from P to T when the spool in central position, the pressure loss should be tested when the spool in the center, the pressure loss is known as △P(P to T)=P – T. But for other spool functions, the spool central position tested is not needed.

5. Inner Leakage Tested – Regulating pressure relief valve (part no.:2-1) until the P port of tested directional valve (part no.:4) is nominal pressure. According to hydraulic solenoid valve spool function and structure, to measure the oil leakage from the A (or B) and T ports while switching the valve spool at each different position. It should be noted before inner leakage testing, the tested valve should be energized and de-energized like normal operation once or twice, then to measure the inner leakage after 30 seconds, in order to get correct number.
For different spool valve function, the leakage measurement diagram is as follows:


Single Directional Solenoid
Valve Spool Leakage Testing

“H” Type Spool Directional
Solenoid Valve Leakage Testing

“E” Type Spool Directional
Solenoid Valve Leakage Testing

“U” Type Spool Directional
Solenoid Valve Leakage Testing


“J” Type Spool Directional
Solenoid Valve Leakage Testing

“L” Type Spool Directional
Solenoid Valve Leakage Testing

“F” Type Spool Directional
Solenoid Valve Leakage Testing

“G” Type Spool Directional
Solenoid Valve Leakage Testing

6. Oil Leakage Tested – Cleaning up the hydraulic solenoid valve and valve testing spacing nearby, checking the valve static seal & dynamic seal as follow;
(1) Static sealing: With a clean absorbent paper sticks to the static seal , to remove the paper after trial, if there is any trace of oil in the absorbent paper is the oil permeability .
(2) Dynamic sealing: Place a white paper at the bottom of dynamic seal on tested valve, to confirm if there is oil drops is dripping on the white paper after the trial.


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