There is a common equipment in life, that is the vacuum pump, he can through a certain method, make a closed space to maintain the vacuum state. Related products are numerous, how to choose the best vacuum pump in 2019?
1. Confirm the installation environment of vacuum pump
Including ambient temperature, relative humidity, atmospheric pressure, air corrosion, dangerous zone level, dust and water requirements.
2. Confirm operating conditions
Refers to liquid suction side level pressure (absolute), discharge side level pressure, intermittent or continuous work, position fixed or moving, installation and maintenance convenience.
3. Confirm the nature of the medium
Including medium name, temperature, density, viscosity, saturated vapor pressure, solid particle diameter and content, gas content, corrosivity, volatility, flammability, toxicity.
4. Select the material of the overcurrent parts of the vacuum pump
According to the physical and chemical properties of the vacuum pumping medium, the following aspects are mainly considered:
(1) corrosion of the medium
The corrosion resistance of the overcurrent parts of the vacuum pump can meet the use requirements, can not pursue too high corrosion resistance, otherwise, will greatly increase the purchase cost of the vacuum pump.
(2) whether the medium contains solid particles
Because the hardness and content of solid particles directly related to the vacuum pump flow components of the durability.
(3) temperature (pressure) of the medium
The higher the temperature (pressure) of the medium, the higher the material strength of the parts of the vacuum pump. Generally, when the temperature is less than 250℃, steel castings or steel pieces should be selected.
(4) medium with requirements for hygiene grade or prohibited pollution
Select the appropriate overflow component material. In addition, the vacuum pump structure should be easy to clean.
5. Select the performance parameters of the vacuum pump
(1) calculation method
A. Flow rate: it is directly related to the production capacity and conveying capacity of the whole device. If the process design can calculate the vacuum pump normal, minimum, maximum three kinds of flow. When choosing vacuum pump, take the maximum flow as the basis, give consideration to the normal flow, in the absence of the maximum flow, usually can be 1.1 times of the normal flow as the maximum flow.
B. Head: generally, the head with a margin of 5%-10% is used for selection. Special attention: centrifugal vacuum pump flow, especially the residual head should not be too large, otherwise, vacuum pump may occur cavitation, resulting in flow, head can not meet the requirements. Once this happens, generally, can be cut impeller outside diameter or turn down the vacuum pump outlet valve remedial measures.
C. Power: generally, the form and size of the power of the vacuum pump shall be selected by the manufacturer and marked in the product samples.
D. Cavitation allowance
Check whether the device cavitation allowance and must cavitation allowance of the vacuum pump match. When it is not satisfied, effective measures should be taken to realize it.
(2) analogy method and experimental method
When the resistance value of the vacuum pump pipeline system cannot be calculated accurately, the flow and head of the vacuum pump can be determined by analogy or test.
6. Select the type of vacuum pump installation
Horizontal, straight, vertical and other types (right Angle, variable Angle, corner, double, detachable) are selected according to pipeline layout and installation site.
7. Determine the number and reserve rate of vacuum pumps
For normal operation of vacuum pump, usually only one, because a large vacuum pump with the parallel operation of two small vacuum pump, (the head and flow rate is the same), big vacuum pump efficiency is higher than the small vacuum pump, so from energy saving point of view would rather choose a large vacuum pump, instead of two small vacuum pump, but in case any of the following circumstances, can consider two vacuum pumps in parallel cooperation:
(1) large flow, a vacuum pump can not reach this flow.
(2) for the vacuum pump that needs 50% reserve rate, it can be equipped with three sets in total.
(3) for some large vacuum pumps, can choose the 70% flow requirements of the vacuum pump parallel operation, no standby vacuum pump, in a vacuum pump maintenance, another vacuum pump still bear the production of 70% of the throughput.
(4) for the vacuum pumps that must be continuously operated 24 hours a day, one shall be operated, one shall be reserved and one shall be maintained, three in all. If necessary, the vacuum pump provider can assist in the selection.