Diffusion Pump Concept And Common Types

- Aug 15, 2019-

Diffusion pump concept and common types

 

The diffusion pump USES a high-speed steam direct injection pump in the throat to decompose the gas molecules into a pump at the bottom of the exhaust. Hosted by Wolfgang gaid in 1915 and using mercury vapors, they are high vacuum free molecular flows that move gas molecules and can be better understood for diffusion than traditional fluid dynamics, the regime operates pumps of the first class. Gad used the name diffusion pump design because he found that the gas could not be diffused on the steam flow based, but would be carried out with it by the exhaust gas.However, the working principle of the jet pump may be more accurately described by air, as diffusion plays an important role, and in other high vacuum pumps. In modern textbooks, diffusion pumps are classified as momentum transfer pumps. Diffusion pumps are widely used in industrial and research applications. Most modern diffusion pumps are used as working media. Cecil lebocchi discovered the possibility of using silicone oil in 1928.

 

oil diffusion pump

The oil diffusion pump operates with a low vapor pressure oil. Its purpose is to achieve higher vacuum (low pressure) by using positive displacement pumps only than is possible. Although its use is primarily related to the high vacuum range (down to 10-9 mbar), today's diffusion pumps generate pressures close to 10-10 mbar when appropriate with modern fluids and accessories. What makes the diffusion pump high and ultra-high vacuum attractive is its high pumping all gas and pumping speed per unit cost lower than other types of pumps used in the same vacuum range. The diffusion pump cannot be discharged directly into the atmosphere, so the front stage mechanical pump is usually used to maintain the outlet pressure of about 0.1 mbar.

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Working principle diagram of six inch oil diffusion pump and oil diffusion pump

 

High speed jet produces boiling liquid and guides the assembly through jet steam. The nozzle inside changes from laminar flow to supersonic and molecular. Usually used in fighter jets to enhance pumping operations. The diffusion pump USES external cooling or air flow or waterline. Due to the influence of steam jet cooling outside the diffusion pump shell, the working fluid is concentrated, recovered, and directed back to the boiler. Pumping gas continues to flow into the pump at increasing pressure on the base, through the diffusion pump outlet where the compression assisted front stage mechanical pump and exhausted environmental pressure is carried out.

 

Unlike turbo molecular and cryogenic pumps, diffusion pumps have no moving parts and are therefore quite durable and reliable. They can operate in the 10-10 to 10-2 millibar range under pressure. They can only drive convection, which is very inefficient for energy.

 

One of the main disadvantages of diffusion pumps is the tendency of backstream oil into vacuum Chambers. This oil can contaminate the surface or interior of the back chamber with hot wire or discharge contacts that may result in deposits of carbon and silicon. Due to backflow, oil diffusion pumps are not suitable for use in highly sensitive analytical equipment or other applications requiring a very clean vacuum environment, but mercury diffusion pumps may be used in ultra high vacuum Chambers with mercury deposition. Usually cold traps and baffles are used to minimize backflow, although in some cases the pumping capacity is lost as a result.

 

A common mistake in the operation of an oil diffusion pump is in the atmosphere of hot oil contact. If this happens, the oil will be burned and replaced. A system should always be cooled to room temperature prior to contact with the atmosphere.

 

One of the main disadvantages of diffusion pumps is the tendency of backstream oil into vacuum Chambers. This oil can contaminate the surface or interior of the back chamber with hot wire or discharge contacts that may result in deposits of carbon and silicon. Due to backflow, oil diffusion pumps are not suitable for use in highly sensitive analytical equipment or other applications requiring a very clean vacuum environment, but mercury diffusion pumps may be used in ultra high vacuum Chambers with mercury deposition. Usually cold traps and baffles are used to minimize backflow, although in some cases the pumping capacity is lost as a result.

 

A common mistake in the operation of an oil diffusion pump is in the atmosphere of hot oil contact. If this happens, the oil will be burned and replaced. A system should always be cooled to room temperature prior to contact with the atmosphere.

 

steam-jet pump

 

Steam ejector is a diffused vacuum distillation and freezing pump popular drying. A steam jet pump is considered to have to be removed from the steam vacuum chamber. Steam ejectors can have one or more stages, and there is no condenser inch between stages.

 

Compressed air injection pump

Among them, the diffusion vacuum pump is a multi-stage compression driven jet air. This is very popular in applications where the object is moved out all over and the vacuum sucker line.

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