As a vacuum (fachsprachlich: negative pressure differential ) is defined as the relative pressure if it is below the ambient pressure. In short, it is often referred to as negative pressure , although negative pressure difference is meant ( there is no negative absolute pressure).
The maximum possible negative pressure is thus achieved with a vacuum and corresponds to the surrounding reference pressure, mostly air pressure, so that up to about 1 bar is possible at sea level. Current standards use 1 bar as the reference pressure (up to 1978 atm ).
Applications of static negative pressure
- Suction cup as a fastening element
- Holding & transporting smooth flat objects with a suction pad
- Clamping workpieces on a vacuum table
- To accelerate filtration or dewatering processes, whereby there are continuous and discontinuous processes
- Use of negative pressure for the brake booster of cars and light trucks as well as for their central locking
Applications with dynamic suction
- A vacuum cleaner creates a vacuum by pushing air out. The effect, which is perceived as suction, arises because the ambient air has a higher density and counteracts this inequality by pushing through the inlet into the device and carrying the dust with it.
- The sewage system has established itself as an application of negative pressure in aviation in modern passenger aircraft. Waste water from the toilets is removed by a negative pressure. For this purpose, a suction pump, typically designed as a radial fan, lowers the pressure in the entire sewage system as required. Since the pressure in the pressurized cabin is kept at the relative overpressure of a maximum of 8,000 ft (2,400 m), the negative pressure in the sewage system can be maintained during the flight with the help of the low atmospheric pressure prevailing outside and the cabin pressure then presses the sewage into the sewage system.
- A space toilet works similarly .