The harm of noise seriously affects people's lives. As the hydraulic system is developing towards high pressure, high speed, and high power, the noise of hydraulic equipment is getting bigger and louder. The noise of hydraulic equipment will directly affect the normal work of hydraulic equipment, and then make the quality and precision of the workpiece produced not up to standard, so we must pay attention to the noise problem of hydraulic equipment, for some important hydraulic equipment noise problems, and also to strictly control them. Using scientific and reasonable control measures to solve the noise problem of hydraulic equipment, and promote the sustainable and stable development of the hydraulic system.
1. Noise analysis of hydraulic equipment
(1) The noise generation mechanism of pumps and motors. The size of the noise is affected by factors such as speed, pressure, and displacement, among which the noise is most affected by speed, and the faster the speed, the greater the noise. In hydraulic equipment, the largest source of noise is the pump and motor, so to reduce the noise of the pump and motor, it is necessary to reduce the speed as much as possible, and according to the speed, with the corresponding displacement and pressure, to achieve the required power. Pumps and motors generally produce noise in three forms, namely audible noise, vibration noise, and pulse noise. Audible noise is the form of noise transmission by air as the medium, vibration noise is the form of noise transmission through the equipment structure, and pulse noise is a form of noise transmission by fluid as the transmission medium. In the hydraulic equipment, the audible noise produced by the hydraulic pump is not large, but it produces a great deal of vibration noise and pulse noise, vibration noise and pulse noise energy is one thousand times the audible noise, and if the energy of the two acts on the pipeline and related equipment, it will lead to greater audible noise, which has a great impact on the hydraulic system, and will also improve the economic benefits of the enterprise. Therefore, we must take reasonable and effective measures to control these three types of noise.
(2) The noise mechanism of the valve. In the hydraulic system, the valve is the main component to control the flow of fluid, and the valve noise is often caused by the change of pressure when the fluid passes through the valve and the noise is more obvious at the throttle valve and the relief valve. Valve noise is generally divided into two types: whistling and hissing. Some of the damaged components of some valves that have been used for a long time will scream, and this noise can be eliminated as long as the damaged components are replaced with new ones. Under normal circumstances, the cause of the roar is resonance, and the noise caused by this reason is difficult to eliminate, and only the valve of other structures can be replaced to eliminate this scream. If the fluid flows through the valve, the pressure changes will produce an unbalanced force, and the bubbles in the fluid will be affected by the unbalanced force and burst and making a hissing sound. The noise produced by the valve is not much, and it is almost inaudible outside the control room. The elimination of this hiss can theoretically be achieved by means of high back pressure, but in general, the working state of the valve cannot be considered as a high back pressure state. Therefore, if in some cases that require high noise standards, a very expensive bubble-free valve can be used to eliminate valve noise.
(3) Pipeline noise generation mechanism. Due to the presence of fluid with periodic pulse vibration in hydraulic pumps and motors, it will also lead to pulse vibration of components and pipelines in the hydraulic system, and it will also produce noise. When the vibration frequency of the pipeline is close to the fixed frequency of the hydraulic system, the resonance generated will lead to greater noise, and in serious cases, it can cause the pipeline and equipment to be damaged, and then accidents occur.
2. Noise control measures
(1) Reduce or eliminate the air content in the hydraulic oil. To effectively reduce the noise generated by the hydraulic pump, it is necessary to reduce or eliminate the air content in the hydraulic oil. Relevant data show that the air content in hydraulic oil is closely related to the noise of the pump. And if the hydraulic oil contains 0.1% of the volume of air, the pump noise will be very significantly larger; If the hydraulic oil contains 1% of the volume of air, the noise control of the pump will fail, and the noise is likely to be larger than the noise of other mechanical transmission devices. Therefore, various effective measures should be taken to reduce the noise of the pump, from reducing or eliminating the air content in the hydraulic oil. The tank can be set higher than the hydraulic pump to prevent air from mixing into the hydraulic oil; Make short and thick hydraulic oil suction inlet pipe, and try to reduce the joint of the pipe to reduce the probability of air mixing into the hydraulic oil; Improve the design of the tank, so that the space above the hydraulic oil level in the tank can accommodate the displacement of the oil pump for two minutes, and then eliminate the small amount of air brought in when the oil is returned; The baffle can also be installed at the appropriate position of the tank to extend the flow distance of the oil return in the tank, to provide enough time for the air in the oil return to escape automatically.
(2) Use of mechanical vibration reduction. The hydraulic pump can also be fixed on the elastic support to reduce the noise of the hydraulic pump. When the hydraulic pump and the elastic support are fixed to each other, an elastic system is formed, and each elastic system will have a unique natural frequency. If the natural frequency is lower than the frequency applied by the outside world, a part of the vibration force will be transmitted to the support, to achieve the effect of vibration isolation. And the lower the natural frequency is compared with the external applied frequency, the less the vibration force is transmitted, and the better the vibration isolation effect is.
(3) Pipeline anti-vibration measures. For the prevention and control of pipeline noise, a hose can be selected, and a flexible connection mode can be adopted when connecting pipelines. In addition, because the hose is a good sound emitter, the short hose should be used as far as possible when arranging the pipeline, and the steel pipe should be installed in the middle, and the hose should be installed at both ends. Only the use of hoses to connect the pipeline can not effectively reduce the vibration of the pipeline, but also needs to perform elastic installation of the pipeline, to reduce some vibration and air noise transmitted to the base. For the spatial arrangement of the pipeline, it is necessary to choose the appropriate pipeline length and a scientifically and reasonably arranged system to prevent the adverse effects of resonance. The vibration and air noise of the pipeline can also be reduced by applying damping materials, and the high-frequency noise can be best suppressed in this way. If possible, hydraulic blocks can be used instead of pipes to reduce vibration. Appropriately increasing the diameter of the pipeline and reducing the flow speed of the hydraulic oil in the pipeline are also anti-vibration measures that can effectively reduce noise.
3. Conclusion
In summary, hydraulic equipment is widely used in people's lives, and the noise of hydraulic equipment is one of the problems that needs to be solved. Noise control of hydraulic equipment needs to run through the design of hydraulic equipment, and reducing noise from the source can really solve the noise problem of hydraulic equipment, and then effectively improving the work efficiency and work quality of hydraulic equipment.
