Current industry activity is strong in production of enclosed cleaning machines which allow cleaning solvents to be used under vacuum conditions. This year and next, I’ll devote several columns to that technology. I’ll try to focus on what’s not commonly known; what’s unusual; and what users should know. This month and next, I’ll cover the engine powering the vacuum vapor degreaser—a vacuum pump.

A VACUUM IS...
...a volume of space which is, to a degree, void of matter. It is technically impossible to produce a vacuum by suction, because fluids¹ can’t be pulled. Rather, the vacuum- producing device expands the volume of space to be evacuated into some larger volume, thereby reducing the pressure in the volume being evacuated. So, a vacuum pump doesn’t pump a vacuum.

TYPES OF VACUUM PUMPS
There are many types of vacuum pumps designed to produce various levels of vacuum for specific types of research, development, and production work, and for use in enclosed cleaning machines. The four types most commonly used with enclosed cleaning machines are described below.

Rotary Vane Vacuum Pumps (also called fixed displacement pumps) are positive displacement devices. This means that the volume of movement within the pump is the same volume of fluid which will be removed from the work chamber during every pump revolution. Of course, the mass of fluid being removed within the work chamber during every revolution depends chiefly upon the pressure and temperature within the work chamber, and so varies within the cycle time of evacuation.