Gap sealing is widely used in many components of the hydraulic system of valve testing machines, and the sealing performance of gap sealing is related to the size of the gap (the leakage amount is proportional to the cube of the gap), pressure difference (the leakage amount is proportional to the pressure difference), sealing oil length (the leakage amount is inversely proportional to the length), processing quality, and oil viscosity. Due to poor lubrication between the motion pairs, improper material selection, and poor machining, assembly, and installation accuracy, early wear can occur, resulting in larger clearances and increased leakage. Secondly, sealing elements are widely used in hydraulic components in the system, and the sealing effect of the sealing elements is related to the sealing material, surface quality, structure, etc.
In the system, if the sealing material is poor, the physical and chemical properties are unstable, the mechanical strength is low, the elasticity and wear resistance are low, etc., leakage occurs due to poor sealing effect; The groove size design for installing seals is unreasonable, and there are also poor dimensional accuracy and roughness. Small pre compression and poor sealing can also cause leakage.
In addition, the surface roughness of the joint surface is poor, the flatness is not good, the deformation after compression and the fastening force is uneven; The oil leakage and return pipelines of the components are not smooth; If the oil temperature is too high, the viscosity of the oil will decrease or the viscosity of the selected oil will be too low; The system pressure is set too high, and the pre compression shrinkage of the seal is too small; Defects in the casing of hydraulic castings can cause an increase in leakage.
2. Measures to reduce internal leakage and eliminate external leakage in the hydraulic system of valve testing bench
Why do we need to conduct pressure and leakage tests on the valves on the valve testing bench?
When using a valve testing bench, we need to conduct pressure and leakage tests on the valve before it can be put into use. Do you understand why we need to conduct pressure and leakage tests on the valve? Below is a detailed introduction for everyone:
The test medium for valves is generally room temperature clean water, and important valves can use kerosene. The safety valve constant pressure test can use nitrogen gas, which is more stable, or steam or air can be used as a substitute. For diaphragm valves, use air for testing. Whether using a new valve or a repaired valve, pressure and leakage tests must be conducted before installation.
Valve pressure test refers to the strength test of the valve body. Valve leakage test refers to the sealing surface tightness test, which is a check of the main performance of the valve.
On site debugging of valve testing bench
There are three steps to perform pressure and leakage testing on the valve using a valve testing bench:
1. Open the valve passage, fill the valve chamber with water (or kerosene), and increase the pressure to the required strength test pressure. Check the valve body, valve cover, gasket, and packing for leaks.
2. Close the valve circuit, pressurize one side of the valve to the nominal pressure, and check for leaks from the other side.
3. Invert the valve and test the opposite side.
1、 The nominal pressure for valve testing ranges from 0.4Mpa to 32Mpa. These commonly used pressure valves have a strength testing pressure of 1.5 times their nominal pressure. The valve sealing test pressure is equal to 1.1 times the nominal pressure.
2、 Valve testing method: The pressure and leakage testing of the valve are carried out on the valve testing bench. The structure of the valve testing platform has a compression component on top and a bottom
