4 major reasons for hydraulic valve malfunction and corresponding preventive measures
Hydraulic valves are almost indispensable hydraulic components in all hydraulic systems. Hydraulic valves play a role in controlling the speed, direction and pressure of actuators in hydraulic systems. Hydraulic valve malfuction will have a huge impact on the entire hydraulic system, and may even directly cause the hydraulic system to fail to operate or cause a machine crash. Today, starting from the relatively concentrated phenomenon of hydraulic valve failure, we made a brief summary of the causes of hydraulic valve failure, hoping to provide you with some reference.
1. Reasons for hydraulic valve failure
1) Mechanical failure
(1) Abrasion: The friction between the moving pairs of mechanical parts such as hydraulic valve cores, valve sleeves, and valve bodies continues to occur during use, causing the size, shape, and surface quality of the parts to change and cause failure.
(2) Fatigue: When working under long-term variable loads, the springs in hydraulic valves will become soft, shortened in length, or completely broken due to fatigue; the valve core and valve seat will also suffer from cracks, peeling, or other damage due to fatigue.
(3) Deformation: When the residual stress of hydraulic valve parts during processing and the external load stress during use exceed the yield strength of the part material, the parts will deform and fail to complete normal functions.
(4) Corrosion: Hydraulic oil is mixed with too much water or acidic substances. After long-term use, it will corrode the relevant parts of the hydraulic valve, causing it to lose its due accuracy and become invalid.
2) Hydraulic clamping
When pressure oil flows through the cylindrical slide valve structure of a hydraulic valve, the radial unbalanced force acting on the valve core causes the valve core to get stuck, which is called ‘hydraulic clamping’.
3) Hydraulic impact
Due to the rapid reversal or closing of the oil passage in the hydraulic system, the oil flowing in the system suddenly reverses or stops flowing, causing the pressure to rise sharply, forming a large pressure peak, which is hydraulic shock.
4) Cavitation
In a hydraulic system, the phenomenon of bubbles caused by pressure drop because of changes in liquid flow rate is called ‘cavitation’. It deteriorates the performance of the hydraulic system and reduce its reliability.
2. Corresponding preventive measures
1) The mechanical failure of hydraulic valves is closely related to the design of the valves and the processing of the parts, so the preventive measures we can take during maintenance are relatively limited.
2) Improving the cleanliness of the hydraulic oil will help reduce the sticking of the valve core due to impurities. When installing the slide valve, tighten the valve body threads as required by the design to avoid sticking of the valve core due to deformation caused by force. Pay attention to the temperature of the hydraulic oil and try to avoid deformation caused by excessive temperature changes. Since the gap between the valve core and the valve body is very small, any slight deformation may cause poor operation and jamming.
3) Try to slow down the switching speed of the reversing valve. You can also slow down the switching speed by adding appropriate damping (throttle port), thereby extending the switching time and reducing the impact. You can also add an accumulator to absorb the impact and reduce the impact. Using a hose instead of a hard pipe can also play a buffering role to a certain extent.
4) Reducing the air content in the hydraulic oil can greatly reduce the occurrence of cavitation, so it is necessary to pay attention to the sealing of the pump and the sealing of the joints in the pipeline to ensure no leakage. Reduce the probability of air mixing into the oil, ensure the oil suction pipeline is unobstructed, ensure that the oil suction pressure is greater than the air separation pressure, and prevent volatile substances such as water from mixing into the oil.
In summary: In addition to processing and manufacturing factors, the mechanical failure of hydraulic valves is mainly related to the management and maintenance of hydraulic equipment. Therefore, do not wait until the hydraulic system fails to work properly before paying attention. Usually, more pre-judgment and pre-processing should be done to eliminate equipment failures caused by hydraulic valve failure in the bud.