What are the types of vacuum pumps used in vacuum graphite furnaces?

There are various types of vacuum pumps used in vacuum graphite furnaces, which can be divided into the following main types based on their working principles, performance characteristics, and applications:

1. Mechanical volumetric vacuum pump
Dry screw vacuum pump
Working principle: By rotating two interlocking screws in the pump chamber, gas is compressed from the inlet to the outlet.
Features: No oil pollution, low noise, low vibration, suitable for industries with high cleanliness requirements, such as semiconductors, electronics, etc. Simultaneously possessing strong corrosion resistance and reliability.
Oil seal rotary vane vacuum pump
Working principle: Seal various working clearances through the circulation of oil, while also providing cooling and lubrication effects.
Features: It can provide high vacuum degree and high pumping rate, suitable for occasions that require high vacuum degree and high pumping rate, such as metallurgy, chemical industry, materials research and other fields. But regular maintenance is required, such as replacing oil and filters.
Roots vacuum pump
Working principle: By rotating two “8” – shaped rotors inside the pump chamber, gas is drawn in from the inlet and compressed to the outlet.
Features: Large pumping capacity, simple structure, easy maintenance, widely used in industries such as chemical and food. However, due to the presence of pulsation during the pumping process, it may not be suitable in certain situations where high stability is required.

2. Jet type vacuum pump
Diffusion pump
Working principle: Utilizing steam flow to drive gas flow.
Characteristics: Mainly used in high vacuum fields, it can achieve extremely high vacuum degree, but the pumping rate is relatively low and requires preheating time. Usually used in fields such as scientific research and semiconductor manufacturing.

3. Momentum transfer pump
Molecular vacuum pump
Working principle: Utilizing the difference in collision probability between gas molecules and the inner surface of the pump under molecular flow conditions to achieve pumping.
Features: Low ultimate pressure, fast pumping speed, especially suitable for applications in high vacuum fields. But it is more sensitive to gas types and temperatures, and has a higher price.

4. Other types
Oil-free vortex vacuum pump
Working principle: It consists of two asymmetric vortex disks, one fixed and the other driven by an eccentric shaft to rotate around the fixed vortex disk.
Characteristics: Environmental protection, high efficiency, low noise, widely used in many fields.
Water ring vacuum pump
Working principle: Compressing and discharging gas through the movement of the water ring.
Features: Simple structure, reliable operation, suitable for various occasions.
When choosing a vacuum pump for use in a vacuum graphite furnace, multiple factors need to be considered, such as the type, composition, temperature, and dust impurities of the gas being pumped, the requirements of the vacuum chamber for oil pollution, investment, and economic indicators for daily maintenance and operation. At the same time, it is necessary to determine the appropriate type and specifications of vacuum pump based on the specific working conditions and requirements of the vacuum graphite furnace.

In summary, there are various types of vacuum pumps used in vacuum graphite furnaces, each with its own characteristics and applicable scope. When choosing, multiple factors should be considered comprehensively to ensure that the selected vacuum pump can meet specific work requirements.