Hydraulic noise analysis:

Noise of 1 plunger pump or motor

(1) the suction phenomenon is caused by the hydraulic pump is one of the main causes of excessive noise. When mixed with air in the oil liquid, vulnerable to the formation of cavitation in the high-pressure area, and to spread the pressure wave form, caused by oil shocks, resulting in cavitation noise generated.

The main reasons are:

The 1 hydraulic pump of the oil filter, plug into the pipeline or oil viscosity is too high, can be caused by the oil pump into the mouth of the high vacuum degree, so that the air infiltration.

The 2 hydraulic pump, pump shaft end seal damage pilot, or into the tubing seal bad, cause air to enter the O 3 tank oil level is too low, so that direct suction pump air into the pipeline.

When there is a higher noise hydraulic pump work, should first check the above site, found that the problem timely treatment.

(2) hydraulic pump excessive wear of internal components, such as the cylinder piston pump with valve plate, the plunger and the plunger hole matched parts wear, strain, so that the hydraulic pump leak serious, when the hydraulic pump output pressure, flow pulsation will produce small flow oil, causing higher noise. At this time may be appropriate to increase the angle pilot system of variable mechanism, to improve the internal leakage of the pump output flow.

Piston servo valve spool, a hydraulic pump to control the flow of the meeting because of partial wear, strain, so that the piston fluctuation in the process of moving, causing the hydraulic pump output flow and pressure fluctuations, resulting in larger vibration and noise in the pump outlet. At this time of wear and tear, injury serious element of brush plating grinding or replacement treatment.

(3) the hydraulic pump valve plate is easily one of the most important components caused by noise. The valve plate in use for surface wear or sludge deposition opening in the unloading groove, will cause the shorter unloading slot and change the unloading position, resulting in the phenomenon of trapped oil, sparking a high noise. In the normal repair process, the grinding flat disk to repair the assignment will also appear shorter unloading slot of the consequences, if not timely at this time due to its slender, will also have a greater noise. In the process of assembly, the large valve plate unloading tank must be installed in the high pressure cavity pump, and pointed the direction and the cylinder rotation relative to the need to, otherwise the system will also bring more noise.

Noise of 2 relief valve

The overflow valve is easy to produce high-frequency noise, the performance of the pilot valve is mainly due to instability, namely noise leading valve chamber before the high-frequency oscillation of combustion pressure causes the air to vibrate.

The main reasons are:

(1) mixed with the air in the oil liquid, the pilot valve before the cavity formed cavitation caused by high-frequency noise. At this time, should be timely exhaust air and to prevent outside air to enter the.

(2) the needle in the process due to the frequent use of open and excessive wear and tear, the cone valve and valve seat can not be closed, causing the pilot flow instability, pressure fluctuations caused by noise, at this time should be repaired or replaced in time.

(3) the pilot valve by the spring fatigue deformation caused by the pressure regulating function is not stable, which makes the pressure fluctuations caused by noise, you should replace the spring.

The noise of the 3 hydraulic cylinders.

(1) the oil mixed with air or hydraulic cylinders in the air is not completely drained, cavitation phenomenon at high pressure caused by a large noise. At this time, must be timely exhaust air.

(2) the cylinder head or piston rod seal tight bend, in the process of movement will also because of other strong noise. At this point, should be the timely replacement of oil seal or straightening the piston rod.

The 4 line noise

Pipe bending die too loose or fixed Nagarze also can generate vibration and noise. Therefore, arrangements should be in the pipeline to avoid dead corner, on off clip shall timely tightening.

Reason two, vibration and noise of hydraulic system and elimination measures

1, the source of vibration and noise

Cause the source of vibration and noise in hydraulic system a lot, generally there are mechanical system, hydraulic pump, hydraulic valve and pipeline and other aspects. The vibration and noise of the mechanical system of vibration and noise of the mechanical system, is mainly caused by mechanical transmission system drives the hydraulic pump, mainly has following several aspects.

1) rotary body imbalance in the practical application, the motor mostly through coupling to drive the hydraulic pump to work, to make the rotary body make the dynamic balance is very difficult, if the imbalance force is too large, it will lead to bigger bending vibration of shaft in the rotation of the noise generated.

2) improper installation of hydraulic system often due to problems caused by installation, vibration and noise. Such as the system of supporting pipeline and poor foundation defects or hydraulic pump and motor shaft concentric, and loose coupling, which will lead to larger vibration and noise.

The 2 hydraulic pump (hydraulic motor) is usually the main hydraulic components of the vibration and noise of the whole hydraulic system. The reason for the vibration and noise of hydraulic pump, on the one hand is due to mechanical vibration, on the other hand is due to the accumulation of liquid pressure and flow changes.

1) periodic variation of pressure and flow of hydraulic pump

Hydraulic pump gear, vane and piston in the oil absorbing, oil pressure in the process, the process makes the corresponding work generates periodic flow and pressure changes in the working cavity, make corresponding production cycle flow and pressure, and then cause the pump flow and pressure pulsation, component caused by hydraulic pump vibration, while the component vibration and the vibration caused by contact with air to produce change in density, thereby generating spread out the noise wave.

2) of cavitation in hydraulic pump

Hydraulic pump at work, if the hydraulic oil suction pipe resistance is too large, at this time, the hydraulic oil to the oil absorption cavity less than full of pump, oil absorption cavity caused by local vacuum, negative pressure is formed. If the pressure just reached the separation of air pressure oil, air originally dissolved in the oil liquid in the can precipitate, forming the free state bubbles. With the pump rotating, the oil liquid with bubbles into the high-pressure zone, this bubble due to high voltage and narrow, rupture and disappeared, the formation of local high pressure high impact

3) the mechanical vibration in the hydraulic pump.

The hydraulic pump is composed of many parts of the component, due to manufacturing errors of parts assembly, noise may be inappropriate for vibration and noise caused by the vibration and noise of hydraulic valve hydraulic system, hydraulic valve 3 generation, because the valve type, the conditions of use and other specific circumstances vary with different. By reason of its occurrence can be divided into mechanical noise and fluid acoustic two categories.

1) hydraulic valve mechanical noise were for the most part is composed of a valve core, valve body, control parts, fasteners, several components such as seals, he is the motion through the external force to the spool, spool movement corresponding to the location so that the liquid flow change, meet the job requirements. In this process, generate mechanical contact the valve moving parts noise.

2) fluid acoustic due to hydraulic valve in the throttled, reversing, the overflow valve body, so that the liquid flow direction and pressure changes, the occurrence, causes vibration of valves and pipe wall, resulting in noise. According to the causes of pressure oscillation can be divided into the cavitation noise, the flow of sound, noise and vibration noise of hydraulic impact. The vibration and noise of the pipeline which is mainly due to the pump, valve and other hydraulic components in the vibration of pipeline caused by the interaction of. Research shows that, when the integer pipeline length is just equal to half the wavelength of the vibration pressure of the pipeline will produce high-frequency noise, strong.

In addition, the external source may also cause pipeline resonance; while the cross-sectional area when the pipeline of sudden changes (rapidly expand and shrink or swerve), will make the liquid flow change, easy to produce turbulence noise.

To prevent oil mixed with air hydraulic systems are often being started in a period of time after a certain period of time, small noise, noise increases, at this time if the observation of hydraulic oil in the tank, can be found in hydraulic oil change to yellow, which was mainly due to oil mixed with tiny air bubbles, so the color changing. In this case the main measures from two aspects, one is the fundamental solution, prevent air from entering the. Two is the mixed oil body air as soon as possible.

The specific method for:

1 pump oil pipe joint seal to be strict, to prevent inhalation of air;

2 the reasonable design of the oil tank. To prevent cavitation in hydraulic valve produce cavitation of hydraulic valve production, mainly do to make oil pump to reduce the resistance. Commonly used measures including oil, with larger diameter pipe, oil filter with large capacity, at the same time, to avoid the oil filter blockage; the pump suction height should be smaller.

To prevent the generation of pipeline internal turbulent flow and vortex

In the design of the hydraulic system pipeline, pipeline section should try to avoid the sudden expansion or contraction; such as the use of pipe, the radius of curvature of the pipe diameter should be more than five times, these measures can effectively prevent the generation of turbulent and swirling flow pipeline.

By using the accumulator absorbing pressure pulsation in the pipeline or the muffler

The pressure pulsation in the pipeline system is the main reason of vibration and noise. The accumulator is arranged in the hydraulic circuit, can effectively absorb vibration, and in the event of vibration absorber is arranged near the site can effectively reduce the system vibration.

Avoiding system resonance occurs

Vibration often occurs in hydraulic system (hydraulic pump, hydraulic motor, motor) caused by bottom plate, pipe and other parts to produce resonance; resonance valve or pump, road and other components of the resulting larger noise. For this phenomenon, by changing the length of the pipeline to change the inherent vibration frequency of pipeline, and some of the valve mounting position is changed to eliminate.

Vibration isolation

The main source of vibration in hydraulic system (pump, motor) often by adding rubber pad or spring and other measures, so that with the bottom (or tank) isolation, also can use the source arranged on the bottom plate isolation and the whole system approach, which can receive the good effect of vibration damping and noise reduction.