Created on:2022-03-29 10:31

Fault analysis and troubleshooting of diverter collector valve

Fault analysis and troubleshooting of diverter collector valve

1. Synchronization failure

The so-called synchronization failure refers to the movement of several actuator elements at the same time. The causes and troubleshooting are as follows.

(1)       Cause analysis.

1) Because the fit clearance between the valve core and the valve body hole is too small, the valve core is also easy to get stuck radially when the system oil is polluted or the oil temperature is too high.

2) The system pressure is too low and the pressure does not rise, resulting in synchronization failure.

3) In the dynamic process of the diverter valve, the synchronization effect can only be achieved after the feedback reaches the balance of the valve core. If the system operates frequently (load pressure changes frequently or reversing frequently), there is no time for feedback and synchronization.

4) For the diverter valve without spring alignment, if no oil passes through when it stops working, the valve core will stop at any position. When the instant of start-up has not played a regulating role, the flow at the two oil ports fluctuates greatly. If the actuator acts immediately, synchronization failure will occur.

5) The diverter valve core is stuck radially due to poor geometric accuracy or burrs.

6) Due to poor installation of hydraulic cylinder (or hydraulic motor) or other reasons, the cylinder action is not flexible, resulting in synchronization failure.

7) Oil channeling due to unequal load pressure in cavities A and B; The orifices inside the diverter valve are connected. When the actuator stops stroke, oil will blow out, which will affect the synchronous action in the next step.

8) If the matching clearance of the valve core of the synchronous valve is too large or the clearance is too large due to wear, the normal operation of the synchronous valve will be affected due to leakage.

(2) Troubleshooting.

1) Pay attention to the cleanliness and temperature of the oil in use to ensure the flexibility of the movement of the valve core.

2) In practical application, ensure that the pressure drop of the primary orifice (fixed orifice) shall not be less than 0.6 ~ 0.8MPa, otherwise the diverter valve will not work and the diverter valve will not work.

3) In practical application, do not use the hydraulic system of synchronous actuator with very frequent action.

4) In practical application, the diverter valve shall be put into use at least 5S after each connection.

5) The valve core shall be repaired and burrs shall be removed to ensure the flexibility of the valve core during feedback movement.

6) Check and correct the installation position of hydraulic cylinder.

7) The hydraulic control check valve can be connected in the synchronous circuit.

8) Brush plating valve core or re matching valve core shall be adopted to ensure proper fit clearance.

2. Large synchronization error

The synchronization error is mainly caused by the symmetry of the fixed orifice of the diverter and collector valve, the oil flow pressure difference before and after the fixed orifice, hydraulic force and leakage. The specific analysis is as follows.

(1) Cause analysis.

1) The flow through the synchronous valve is too small, or the pressure difference in and out of the oil chamber is too small, which will reduce the front and rear pressure difference of the fixed orifices on both sides.

2) When the synchronous valve is installed vertically, the synchronization accuracy will be affected by the self weight of the valve core.

3) The radial clamping force of the valve core is large, resulting in the increase of the movement resistance of the valve core. Therefore, the hydraulic oil pressure difference between the K and G chambers that push the valve core to achieve automatic compensation needs to be increased, so that the difference between the oil hydraulic pressure difference before and after the fixed orifices on the left and right sides is large. According to the orifice flow formula, the flow difference through cavities A and B will be large, and the speed synchronization error will be large.

4) The load pressure deviation (PG Pb) is large, which affects the synchronization accuracy. Therefore, the hydrodynamic imbalance acting on the valve core affects the feedback balance speed and difficulty of the valve core.

5) The load pressure vibrates frequently and strongly. At this time, the shunt valve will produce shunt error and its accumulation in the process of automatic regulation, which will affect the synchronization accuracy.

6) There are many components connected between the diverter valve and the actuator, and their leakage is large, which increases the synchronization error of the circuit.

7) Shunt valves can be connected in series, parallel or series parallel combination in synchronous system. When connected in series, the speed synchronization error of the system is the superposition value of the speed synchronization error of each shunt valve connected in series. Therefore, the more valves in series, the greater the speed synchronization error. Therefore, from the point of view of reducing the error accumulation of speed synchronization valve, the system synchronization error can be smaller in parallel (the average value of each speed synchronization error).

8) The synchronous valve is wrongly installed into a spring with high stiffness. Under the condition of ensuring that the valve core can be reset, reduce the spring stiffness or even cancel the spring, which can improve the synchronization accuracy.

(2) Troubleshooting.

1) Properly increase the differential pressure in and out of the oil chamber, ensure that the differential pressure is generally not less than 0.8MPa, and the service flow shall not be less than 25% of the nominal flow.

2) Synchronous valves shall be installed horizontally.

3) The causes of radial clamping force shall be eliminated one by one.

4) The solution can adopt the method shown in Figure 117, and use the correction orifice to reduce or eliminate the influence of hydrodynamic force on the accuracy of speed synchronization. That is, part of the flow through the branch with large load pressure flows through the modified orifice to the branch with small load pressure, which can improve the accuracy of speed synchronization. This can be achieved by setting a correction orifice inside the valve body flow passage or outside the valve body as shown in the figure.

5) Load fluctuations must be minimized.

6) Generally, other control elements are not connected between the diverter valve and the actuator as far as possible to avoid increasing the synchronization error of the circuit due to the different leakage of these control elements or other reasons.

7) Shunt valves shall be connected in series as little as possible in the synchronous system, and shall be mainly connected in parallel or combined in series and parallel.

8) The wrong spring shall be corrected to the spring with appropriate stiffness.

3. The end-point action of the actuator is abnormal

In the synchronous system with synchronous valve, sometimes one actuator moves to the end point, while the other actuator stops moving and cannot reach the end point. This is due to the blockage of the normally open hole on the valve sleeve. If the normal through hole on the right side is blocked, when the movement of the left actuator reaches the end point, the pressure in chamber K increases, causing the valve core to move to the right, causing the right 4 variable throttle hole to close. At this time, the right side 4 is usually blocked by the small hole fork because the variable throttle hole is closed, so there is no flow in the G cavity, so that the right actuator stops moving. When this situation is found, it shall be cleaned in time to keep the normally open hole unblocked.

In addition, adjustable limiters shall be set at both ends of the diverter valve core, which can also avoid the above situation. That is, the pressure at the oil outlet of the diverter valve that reaches the end of the stroke first increases, and the valve core moves. Due to the adjustable stopper, it is not possible to completely close the other oil port and the other hydraulic cylinder cannot continue to move to the end of the stroke. The accumulated error can also be eliminated by adjustment.

 

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