Technical Article

hydraulic cylinder leakage detection - Advantages, disadvantages, and improvements of the pressure h

The advantages and disadvantages of pressure holding detection method 

The pressure holding method is a qualitative detection method for internal leakage in hydraulic cylinders, which directly detects the leakage situation through pressure drop. It is easy to operate and has a short time. Taking the detection of internal leakage from a rodless chamber to a rodless chamber as an example, while ensuring no external leakage, the electromagnetic directional valve works in the left position, the hydraulic cylinder rodless chamber oil pressure is the test pressure, and the rodless chamber oil pressure is zero. When the piston rod is fully extended to the maximum stroke position, the hydraulic control check valve is controlled to maintain pressure. During the pressure holding process, due to the lack of oil pressure in the rodless chamber, the piston body remains stationary. If there is no internal leakage in the tested hydraulic cylinder, the holding pressure does not change, and there is no pressure drop; On the contrary, if there is a pressure drop, there will be internal leakage in the tested hydraulic cylinder. The use of this method to determine whether the internal leakage of the tested hydraulic cylinder meets national standards often relies on the experience of the operator, but there is no clear criterion for determining the specific amount of internal leakage and whether it is qualified.

Improvement of pressure holding detection method

Under the condition of ensuring that the hydraulic cylinder has no external leakage, the pressure drop observed by the pressure holding method comes from three aspects: firstly, the hydraulic test bench itself is a hydraulic system, including various hydraulic valves, and there is internal leakage in the system itself, especially for hydraulic test benches that have been used for a long time, the internal leakage is greater; The second is the leakage at the connection of the pressure test joint, including the internal leakage of the hydraulic valve inside the joint; The third issue is the internal leakage of the tested hydraulic cylinder.

To accurately determine the pressure drop value of the hydraulic cylinder, it is necessary to first eliminate the internal leakage at the connection between the hydraulic test bench and the pressure test joint, but the internal leakage of these two cannot be completely eliminated in practical work. Therefore, it is necessary to detect the internal leakage at the connection between the hydraulic test bench and the pressure test joint before conducting the hydraulic cylinder leakage test.

After determining the internal leakage pressure drop value at the connection between the hydraulic test bench and the pressure test joint, conduct an internal leakage test on the hydraulic cylinder. The pressure drop value obtained from the final test minus the pressure drop value caused by internal leakage at the connection between the hydraulic test bench and the pressure test joint is the pressure drop value caused by internal leakage of the hydraulic cylinder. Finally, the accurate hydraulic cylinder leakage is calculated by converting the pressure drop and internal leakage.