Customers often ask questions about the selection of vacuum pumps. In fact, the selection of vacuum pumps mainly depends on the pumping rate and the ultimate vacuum degree. It is not difficult to know that the ultimate vacuum degree is determined by the production process conditions. However, when choosing the pumping capacity of the vacuum pump, there is often a lack of data, which makes it helpless. Next, the EVP vacuum pump manufacturer will introduce some calculation methods for your reference.
The pumping capacity of vacuum pumps should include the non-condensable gas released from the production process, the dissolved air released from cooling water, the equivalent value of saturated vapor pressure of the fluid in the process, and the air leaked from the imprecise connection between equipment and pipeline. However, since the amount of non-condensable gas released during the process is generally small and negligible, the key components are the last two.
1. The amount of air leaking from the vacuum system can be determined by either of the following four methods:
1. According to the total volume of vacuum system equipment and pipeline;
2. Equipment and pipeline accessories assembled according to vacuum system;
Although this method is conservative, the results obtained can be adapted to the situation where air leakage fluctuates greatly and is suitable for operation.
3. According to the joint length of vacuum equipment, pipeline and other accessories, the air leakage per meter is calculated as 0.05-0.07 [kg/h], and then doubled.
Secondly, some parameters of vacuum pump are selected.
1. The limit pressure of the vacuum pump should meet the working pressure of the process. Usually, the limit pressure of the pump is about one order of magnitude lower than the process requirement.
2. Each pump has a certain range of working pressure. Therefore, the working point of the pump should be selected in this range, instead of allowing it to work outside the allowable working pressure for a long time.
3. Under its working pressure, vacuum pump should be able to discharge all the gas produced in the process of vacuum equipment.
4. Whether the vibration caused by the vacuum pump during working has an impact on the technological process and environment, if the technological process is not allowed, the non-vibration pump should be selected or anti-vibration measures should be taken.
5. Understand the composition of the extracted gas. The gas contains no condensable vapor, particulate dust and corrosiveness. When choosing a vacuum pump, it is necessary to know the gas composition and select the appropriate pump for the pumped gas. If the gas contains steam, particles, and corrosive gas, it should be considered to install auxiliary equipment such as condenser, dust collector in the intake pipeline of the pump.
6. When choosing oil seal vacuum pump, we should consider the influence of oil vapor (oil fume) discharged from the vacuum pump on the environment. If the environment is not allowed to be polluted, oil-free vacuum pumps should be selected, or oil vapor should be discharged outdoors.
7. Selection of vacuum unit: When using a vacuum pump can not meet the requirements of pumping and vacuum, several pumps need to be combined to complement each other in order to meet the technological requirements.
Finally, if we consider the cost, we can consider the preferential price of domestic vacuum pump. If the economy permits, we can consider the import, and the service life is longer.