Mean air pressure at sea level is 1000 millibars (mb) which is the equivalent of 1 kg per cm². If the air is now extracted under a suction housing, the ambient air pressure presses the suction housing to the surface.
In vacuum lifting technology, the vacuum is generated by an electric pump which initially evacuates (sucks the air out of) a tank kept directly at the machine. The vacuum is generated to 98 %.
The pump runs continuously all the time the machine is working. It is even capable of withstanding higher temperatures during continuous operation (oil circulation cooling).
For lifting purposes, the suction housings are connected with the tank by means of an electric valve and vacuum pipes. The valve is opened by pressing a button to force the air out of the suction housing into the tank. This happens suddenly so that the suction housing is also suddenly pressed to the part being lifted. The vacuum area is now expanded by the space underneath the suction housing. Between the suction housing and the part that is to lift acts the rubber seal. The seals have an extremely long service life. New seals often hold the vacuum for days at a time, even when the pump is switched off. Over time, wear-and-tear together with mechanical loads can result in minor vacuum losses. This is also one reason why the pump must be kept running while the machine is in use!