Analysis of the causes of hydraulic valve failure: cavitation

In this paper, we will analyze the last cause of the failure of the Hydraulic Valve in the future: cavitation.
In this paper, we will analyze the last cause of the failure of the hydraulic valve in the future: cavitation.

In a hydraulic system, a phenomenon in which a bubble is caused by a pressure drop due to a change in a liquid flow rate is called "cavitation."

1, the cause of cavitation

1 When the pressure of a part of the hydraulic system is lower than the critical pressure of air separation dissolved in the oil at a specific temperature, the originally dissolved air in the oil will be largely separated to form bubbles.

2 If the pressure continues to drop, when the saturated vapor pressure of the solution is lower than the specific temperature, the oil boils and evaporates rapidly, generating a large number of bubbles, which are mixed in the working oil to make the oil originally filled in the pipe or the component become Intermittent state, forming a "cavitation."

2, the hazards of air pockets

1 When the bubble flows into the high pressure zone with the oil, it suddenly shrinks. Some of them burst rapidly under the impact of the high pressure oil flow, recondensing into a liquid, reducing the volume occupied by the original to form a "vacuum", and the surrounding high pressure oil particles At a very fast speed, it rushes toward the vacuum center, causing a partial violent pressure shock;

2 At the same time, the kinetic energy of the oil particle is converted into pressure energy, where the pressure and temperature rise sharply, causing severe vibration and strong noise.

3 The surface of the component near the condensation of the bubble is repeatedly subjected to pressure shock under high temperature conditions, and the acid gas separated in the oil has a certain corrosive effect, causing the surface material to peel off, forming a small pitting and a honeycomb, that is, generating Cavitation.

4 Cavitation and cavitation deteriorate the hydraulic system performance and reduce reliability.

3, the prevention of cavitation

1 The main measures of hydraulic equipment to prevent cavitation and cavitation are to reduce the air content in the oil. Pay attention to the shaft seal of the pump in the system, the sealing at the pipe joint, the height of the oil level, the inlet port of the return pipe, etc. Inhale the air.

2 Pay attention to the oil temperature to prevent the oil from vaporizing at high temperature.

3 The oil suction pipeline should be large enough and kept clear, so that the system oil pressure is higher than the critical pressure of gas oil separation.

4 Prevent the hydraulic oil from mixing with volatile substances and moisture, so as not to volatilize in the low pressure zone to form bubbles and become steam bubbles.