Causes of Vibration and Noise in Hydraulic System

1. There are many sources of vibration and noise in the hydraulic system, including mechanical systems, hydraulic pumps, hydraulic valves, and pipelines. The vibration and noise of the mechanical system are mainly caused by the mechanical transmission system that drives the hydraulic pump, mainly in the following aspects.

1) Unbalance of the rotating body

In practical applications, most motors drive hydraulic pumps through couplings, and it is very difficult to achieve a complete dynamic balance of these rotating bodies. Bending vibration produces noise.

2) Improper installation

Hydraulic systems often cause vibration and noise due to installation problems. If the system pipeline is poorly supported and the foundation is defective, the hydraulic pump and the motor shaft are not concentric, and the coupling is loose, which will cause greater vibration and noise.

1. The hydraulic pump (hydraulic motor) is usually the most important hydraulic component that produces vibration and noise in the entire hydraulic system. The reason for the vibration and noise of the hydraulic pump is due to the mechanical vibration on the one hand, and the pressure flow of the liquid on the other hand. caused by accumulation changes.

1) Periodic changes in hydraulic pump pressure and flow

During the process of oil suction and oil pressure, the gears, vanes, and plugs of the hydraulic pump make the corresponding work generate periodic flow and pressure, and the corresponding working chamber produces periodic flow and pressure changes, which in turn causes the pump The flow and pressure pulsation of the hydraulic pump to cause the components of the hydraulic pump to vibrate, and the vibration of the components causes the vibration of the air in contact with it to change in density, and then the sound pressure wave that generates noise spreads out.

2) Cavitation phenomenon of hydraulic pump

When the hydraulic pump is working, if the resistance of the hydraulic oil suction pipeline is too large, at this time, the hydraulic oil will not be able to fill the suction chamber of the pump, resulting in a partial vacuum in the suction chamber, forming a negative pressure. If this pressure just reaches the air separation pressure of the oil When the pump is pumped, the air originally dissolved in the oil will be precipitated in large quantities to form free air bubbles. With the rotation of the pump, the oil with air bubbles is transferred to the high-pressure area, and the air bubbles are reduced due to the high pressure. Rupture and disappear, forming a high local high-frequency pressure shock.

3) Mechanical vibration in the hydraulic pump

The hydraulic pump is composed of many parts. Due to the manufacturing error of the parts, improper assembly may cause vibration and noise in the hydraulic system.

1. The noise generated by the hydraulic valve varies depending on the type of valve and the specific conditions of use. According to the cause of its occurrence, it can be roughly divided into two categories: mechanical sound and fluid sound.

1) Mechanical sound

Most hydraulic valves are composed of a valve core, valve body, control parts, fasteners, seals, and other parts. They move the valve core through external force, and the valve core moves to the corresponding position to change the liquid flow to meet the Work requirements. During this process, the mechanical contact of the moving parts in the valve generates noise.

2) Fluid sound

When the hydraulic valve is throttling, reversing, and overflowing, the flow rate, direction, and back pressure of the liquid flow in the valve body undergo various changes, resulting in the vibration of the valve parts and the wall surface of the pipeline, resulting in noise. According to the causes of pressure vibration, it can be divided into cavitation sound, flow sound, hydraulic impact sound, and shock sound. Vibration and noise of pipeline This is mainly caused by the interaction of the vibration of hydraulic components such as pumps and valves on the pipeline. Studies have shown that when the length of the pipeline is exactly equal to an integer multiple of half the wavelength of the vibration pressure, the pipeline will generate strong high-frequency noise.

In addition, external vibration sources may also cause pipeline resonance; when the cross-sectional area of ​​the pipeline changes suddenly (sudden expansion and contraction or sharp turn), the liquid flow in it will change, which is prone to turbulence and noise.

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