Sources and solutions for noise in slide valve vacuum pumps

Mechanical impact noise is the main component of the noise in a valve pump. During normal operation, the valve body and the inner wall of the pump body (at the junction of the large and small cylinders on the intake side) undergo mechanical impact, generating strong mechanical impact noise. Factors affecting mechanical impact noise include: the clearance between the pump body and the valve ring, the clearance between the eccentric wheel and the valve ring, and the offset between the pump shaft center and the center of the large cylinder in the pump body. In design, the clearance at the impact point is usually adjusted to reduce or even eliminate the impact, thereby lowering the mechanical impact noise of the valve pump.
1. Liquid impact noise and gas-liquid discharge noise are significant components of pump noise.

During the compression process of a slide valve pump, the slide valve drives the pump oil at high speed against the pump cylinder wall and slide valve rod near the exhaust port, generating strong liquid impact noise. Furthermore, during the exhaust process, the high-speed passage of lubricating oil and gas through the exhaust channel produces strong gas-liquid discharge noise. These two types of noise are most pronounced at the end of the exhaust phase. To reduce these two types of noise, a lower rotational speed and a smaller pump cylinder diameter can be selected during the design phase to reduce the velocity of liquid impact and gas-liquid discharge, thus reducing noise. During normal pump operation, reducing the oil intake pump reduces the amount of oil impacting the pump wall and the amount of oil discharged, further reducing noise. Gas-liquid discharge noise can also be reduced by improving the exhaust valve's flow path, maximizing the channel area, and decreasing the velocity of the lubricating oil passing through the exhaust valve.
2. Bearing noise is uncommon in slide valve pump noise.

Slide valve pumps operate at low speeds, and the bearings are well-lubricated, resulting in extremely low noise levels during normal operation. Bearing noise primarily refers to the noise emitted when the bearings are not functioning properly. If the bearings in a slide valve pump are damaged during processing, transportation, or installation, they may produce an abnormal "ticking" sound during normal operation. This noise has a low frequency and weak intensity, but is still noticeable.

3. Cavitation noise is rarely seen in slide valve pump noise. For medium and large slide valve pumps, the pump speed should not be too high, otherwise cavitation may occur, reducing the pump's lifespan.

4. The oil tank is also a factor affecting the noise of a slide valve pump.
Welded steel plate oil tanks are prone to vibration; cast iron oil tanks are less prone to vibration, and cast iron itself has sound-absorbing properties, so using a cast iron oil tank can reduce pump noise by 2-3 decibels (A). The built-in oil-gas separator in the oil tank can have its obstruction appropriately increased without affecting the exhaust pressure, further enhancing the noise reduction effect, which can also reduce pump noise by 1-2 decibels.
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