Vacuum Pumps

Gas transfer pumps transfer gas molecules via momentum exchange or positive displacement, and the gas is slightly above atmospheric pressure when it is expelled. 

Kinetic transfer pumps work on the principle of momentum transfer and can achieve high compression ratios at low pressures.

Positive displacement pumps work by isolating a quantity of gas, compressing it, sealing it in the chamber, and moving it through the pump at high pressure before expelling it. These pumps create low vacuums and two are often used together to provide a higher vacuum. Examples of positive displacement vacuum pumps are liquid ring vacuum pumps and roots blowers.

Entrapment pumps, also known as capture pumps, operate at low flow rates, but have the ability to produce extremely high vacuum (down to 19-12Torr). They do not have any moving parts, creating an oil-free vacuum, and operate by using either chemical reaction, cryogenic condensation or ionic reaction. Entrapment pumps can be used with positive displacement pumps or kinetic transfer pumps to create an ultra-high vacuum.

Vacuum pumps are classified as wet or dry depending on whether the compressed gas is exposed to liquid or not during the process. Wet pumps are lubricated by oil or water which can contaminate the gas, whereas dry pumps do not have fluid in the pumped gas, relying on a tight seal or diaphragm to separate the gas from the pumping mechanism. However, dry pumps can never be entirely oil-free as lubrication is often used in the pump gears and bearings and there is always a risk of contamination.

The main purpose of centrifugal pumps is to transfer fluids through the pressure created by the centrifugal force.

Similar to rotary vane pumps, a low friction pump where the rotor is the only moving part. They can be single or multistage.

Claw vacuum pumps are based on static compression systems and generate contact-free vacuum. They have two rotors that turn in opposite directions within the compressor housing and synchronised by a precision gear.

Using two parallel, synchronised rotors, rotary screw pumps use opposing rotation to trap gas and move it into the compression chamber.

Gas is taken in via the side channel where a rotating impeller forces it in the direction of rotation. The centrifugal force blows the gas from the impeller blades and discharges it from the pump.

Positive displacement blowers are reliable and durable and have been in use since the mid-19th century. The air flow is dependent on the position and direction of two or three conjugate rotors, with isochoric compression (also known as external compression) the result of the rotors moving against the wall of the chamber. The pressure is increased by intermittently transporting air into the system creating resistance in order to achieve the relevant pressure increase. The blower operates at a controlled output level to overcome this resistance.

Rotary screw blowers use two ‘screw’ rotors that rotate in different directions drawing the air between them, using the rotors to trap the gas within the casing wall, and compressing the air as the space decreases. It produces a steady air flow with minimal vibrations. The rotary screw blower operates without the need for lubrication in the compression chamber which, combined with the fact that the rotors never touch each other, produces optimal performance and maintains extremely high standards of purity. They only use a comparatively small amount of energy, making them more cost-efficient to run at the same time as being easy to maintain as there is less wear and tear.

Turbo blowers offer a low energy, low cost solution. They have been designed to work under constant pressure, delivering compressed air without pulsations. Radial blades are used to draw air into the impeller where it is forced through the diffusers and volute. Working on Bernoulli’s principle of pressure being inversely proportional to velocity squared, kinetic energy is converted into pressure, and velocity energy converted into pressure energy.

Robuschi has developed an innovative aeration turbo blower specifically for wastewater treatment. It has been designed for efficiency, reliability, and environmental impact. It can deliver pressures up to 1,500 mbar(g) and airflow rates of up to 26,500 m³/h. Maintenance costs are decreased by the use of a high speed magnet motor coupled to the impeller. Turbo blowers have low vibration and noise levels, and the air foil bearings do not need to be oil lubricated, guaranteeing cleaner air.