Simply put, vacuum pumps are mechanical devices that enable the removal of air and gas molecules from a sealed area to create an area devoid of air and/or gas. Generally, their purpose is to clean and seal. Vacuum pumps come in wet or dry variants depending on the media being pumped through them.
Vacuum Pumps can be used in a wide variety of industries and applications to remove air and gas molecules from a process including the food and beverage industry, semiconductor and electronics industry, pulp and paper, medical, plastics and woodworking to name but a few. Common examples of vacuum pump applications include vacuum packaging machines, pick and place machines, drying of components, bottle filling and holding and lifting.
Pumping speed, that is, the rate at which gas and air can be removed from a volume is the main factor that defines a vacuum pump’s performance. More specifically, pumping speed refers to the volume flow rate of a pump at its inlet, often measured in volume per unit of time.
It is important to note that the pumping rate depends on the chemical composition of the gas being pumped as well as the type of pump that is being used. For example, momentum transfer and entrapment pumps are more effective on some gases than others.
Another measure of a vacuum pump’s performance is its throughput. Throughput measures pumping speed multiplied by the gas pressure at the inlet by calculating the number of molecules pumped out per unit of time at a constant temperature.
Throughput is also useful when assessing a leak in the system. It allows you to measure the volume leak rate multiplied by the pressure at the vacuum side of the leak. This way the leak throughput can be compared to the pump throughput.
In addition, positive displacement and momentum transfer pumps maintain a constant pumping speed. However, as the chamber's pressure drops, and the volume contains less and less mass, the throughput and mass flow rate drop exponentially although the pumping speed remains constant. Meanwhile, the leakage, evaporation, sublimation and backstreaming rates continue to produce a constant throughput into the system.
The most expensive component in the lifespan cost of a vacuum pump is its energy consumption. In fact, a vacuum pump’s energy consumption typically costs five times more than its purchase price over the pump’s lifespan while maintenance costs are about 30%.
The key is to choose the most energy efficient and reliable system, which will allow you to reduce the total cost of ownership dramatically.
When choosing a vacuum pump, a deciding factor is the quality and desired vacuum level of the pump. There are three types of vacuum:
The differentiating factor is the scarcity of the number of molecules obtained, which is measured by the pressure exerted by residual gases. The lower the pressure, the more the number of molecules per cm³, and as a result, the vacuum level quality is higher.
Industrial vacuum pumps are categorized as ultra-high vacuum (UHV) types. An UHV type is characterised by pressures lower than about 100 nanopascal (10−7 pascal, 10−9 mbar, ~10−9 torr). These are typically two stage vacuum pumps.
A two stage vacuum pump design is generally preferred when seeking to produce UHV vacuum levels in an industrial pump capacity.
A two stage design contains two sets of rotors and vanes, which allow it to utilize a low vacuum stage and a high vacuum stage. The high vacuum stage takes in process gas and transfers it to a second, low vacuum stage that compresses the gas to atmospheric pressure, improving the vacuum performance of the pump.
If deeper pressure with better vacuum level performance is necessary, a two stage vacuum pump is the better solution.