Vacuum pressure, created by any pressure lower than atmospheric pressure, is the method of choice for companies to move products. The two most popular vacuum pump contenders are compressed air-driven pumps, commonly referred to as generators, and electromechanical pumps.

Compressed-air driven vacuum pumps rely on Bernouli's Principle, which states that there is a consistent relationship between pressure and velocity: high velocity of a fluid leads to low pressure, and vice-versa. Air-driven pumps force compressed air through an orifice or nozzle, increasing the velocity and creating low-pressure air.

A mechanical pump uses the same pumping mechanism as a compressor, except that the unit is installed so that air is drawn from a closed volume and exhausted to the atmosphere. Rotary vane pumps are the most commonly used mechanical pumps.

How Air-Driven and Rotary Pumps Compare

• Lubrication. Some rotary vane pumps require lubrication, and the precisely correct amount of lubrication at that. Too much lubrication can result in an oil feed rate that is too fast, or a heavy oil condensation. Insufficient lubrication can lead to too slow an oil feed rate, and eventually, complete pump failure. Multistage air-driven pumps (see diagram) have no gears or moving parts that create friction, so they require no lubrication -- another environmentally friendly, maintenance-reducing advantage.


• Rebuilding. The long list of standard replacement parts that comes with mechanical pumps typically includes shaft seals, gaskets, O-rings, valves, bearings, vanes, springs, and many other items. The wear and tear on these parts may require a total rebuild (and a need to keep spare pumps on standby). Air-driven pumps have practically no moving parts and require little or no maintenance. The only moving parts are flap valves that open and close internal chambers as the pump adjusts to varying loads.


• Continuous vs intermittent operation. A rotary vane pump's electric motor can't be cycled on and off to break a vacuum. A "vacuum valve" component can be added to accomplish intermittent use of the vacuum, but the rotary vane pump motor must run continuously. In comparison, multistage air-driven pumps are far more energy efficient. The intermittent use of these pumps is controlled by a pneumatic valve, which is simply cycled to turn the vacuum as well as the pump on or off. These pumps do not need to maintain continuous operation.