Vacuum systems are used for picking up objects and for cleaning of dirt. The former use is common in manufacturing systems where tiny objects can be sucked onto a robotic arm and be carried to another process. Very often the vacuum systems are built into the manufacturing machines. In other cases, there is a central vacuum system to carry out this function. For cleaning of dirt, this can be compared to the household vacuum cleaner. A central vacuum system for removal of dirt has distribution pipes to reach a wide area.
For a vacuum system that need not achieve very low vacuum, the pump is usually a centrifugal blower. The blower can be designed for high-speed rotation and vacuum up to 6 inches water gauge can be achieved. Centrifugal blowers are not able to achieve very high vacuums. For high vacuums, either a vane vacuum pump, or a water ring vacuum pump is used.
The vane pump is the same type described in the section on positive displacement pump. The only difference is the direction of the flow and the fluid that is being pumped.
For the vacuum vane pump, the fluid is air. The direction of flow is exactly opposite to the pump. It is pumped out instead of in.
To maintain the seal between the vane and the pump housing some oil is introduced. The oil also serves to lubricate the rubbing parts.
The water ring vacuum pump has a circular impeller rotating in an elliptical housing. Some water is introduced into this housing, not to fill it completely, but to maintain a water seal between the impeller perimeter and the housing. When the impeller is rotated, the water inside is flung out to form a ring in the shape of the housing. The air volume in the impeller becomes smaller when it passes through the narrow part of the housing. Similarly the volume becomes bigger when it passes through the wider part of the housing. The effect is like a column of water moving in a reciprocating manner to suck and compress the air. The suction and discharge ports are arranged accordingly.
The water ring vacuum pump may also contain systems for cooling the water.
Usually a vacuum reservoir is installed to act as a buffer against fluctuations in vacuum pressures caused by variation in usage.
It is extremely difficult to check for leaks in a vacuum system. Very often leaks cannot be heard, felt or seen. Ultrasonic listening devices can be helpful to detect and trace the locations of leaks.