How to select vacuum pump
Customers often ask about the selection of vacuum pump. In fact, the selection of vacuum pump is mainly based on the two indexes of pumping rate and limiting vacuum degree. It is not difficult to know that the limit vacuum degree is determined by the production process conditions. However, when selecting the vacuum pump, there is often a lack of data on the pumping capacity of the vacuum pump. The following vacuum pump manufacturer introduces some calculation methods for reference.
The pumping volume of vacuum pump should include: non condensable gas released from the production process, dissolved air released from cooling water, equivalent position of saturated vapor pressure of fluid in the process, and air leakage from the loose connection of equipment and pipeline. However, since the amount of non condensable gas released in the process is generally very small and can be ignored, the key components are the last two items.
The amount of air leaking from the vacuum system can be determined by one of the following four methods:
1. According to the total volume of vacuum system equipment and pipeline;
2. Equipment and piping accessories assembled according to the vacuum system;
Although this method is conservative, the results obtained can adapt to the situation of large fluctuation of air leakage and is suitable for operation.
3. According to the joint length of vacuum equipment, pipeline and other accessories, the air leakage per meter is 0.05 ~ 0.07 [kg/gh], and then doubled.
Then some parameters of vacuum pump are selected
1. The limit pressure of vacuum pump should meet the working pressure of the process. Generally, the limit pressure of vacuum pump is lower than the process requirement by about one order of magnitude.
2. Each kind of vacuum pump has a certain working pressure range. Therefore, the working point of vacuum pump should be selected in this range, instead of allowing it to work at the allowable working pressure for a long time.
3. Under its working pressure, the vacuum pump should be able to discharge all the gas produced in the process of vacuum equipment.
4. If the process is not allowed, the pump without vibration should be selected or anti vibration measures should be taken.
5. Understand the composition of the extracted gas, whether there is condensable steam in the gas, whether there is particulate dust, whether there is corrosiveness, etc. When choosing the vacuum pump, it is necessary to know the gas composition and select the corresponding pump for the extracted gas. If the gas contains steam, particles and corrosive gas, it should be considered to install auxiliary equipment such as condenser and dust collector on the air inlet pipeline of the pump.
6. When choosing oil seal vacuum pump, the influence of oil vapor (oil fume) discharged from vacuum pump on environment should be considered. If the environment does not allow pollution, oil-free vacuum pump should be selected, or the oil vapor should be discharged to the outdoor.
7. Selection of vacuum unit: when using a vacuum pump can not meet the requirements of pumping and vacuum, several vacuum pumps need to be combined to complement each other to meet the process requirements.