Compressed air from A to Z

Here you can find technical terms and explanations on the topic of compressed air

1. What is an aftercooler?
The compressed air is cooled in the aftercooler; the humidity is thus condensed from the air. Air and condensation flow separately into the vessel.

2. What is an intake filter?
The air is absorbed via the intake filter and cleaned. The service life of the intake filter is largely dependent on the operational conditions of the compressor.

3. What is the fan wheel?
The fan wheel cools the entire unit, in particular the aftercooler and cylinder. For AC motors it is necessary to observe the direction of rotation marked by the red arrow.

4. What is the purpose of the safety valve?
Because of legal requirements a safety valve is necessary, which blows off at a defined pressure, e.g. 1-2 bar above ultimate pressure.

5. What effect does the cylinder have?
The intake air is compressed in the cylinder. Piston compressors are available in one- and two-cylinder versions. For two-cylinders in series or as a V-motor we distinguish between the single-stage and two-stage design.
Single-stage: The compression is effected per cylinder at ultimate pressure.
Two-stage: Pre-compression in the first cylinder and post-compression in the second cylinder.

6. What is the purpose of the pressure switch?
The pressure switch automatically controls the on and off impulses of the compressor using the vessel pressure. When the maximum pressure is reached the compressor automatically switches off. If the pressure drops by approx. 2 bar through removal of air, the compressor is automatically restarted.

7. What is the purpose of the check valve?
The check valve prevents air from the vessel returning to the compressor.

8. What is the load relieving valve?
The load relieving valve is installed under the pressure switch. It releases existing excess pressure when the compressor is automatically switched off. The compressor can start load-free.
Caution: In the event of a power failure there is no automatic relief by switching off and on.

9. What is the purpose of the pressure vessel?
It is used as an air cell, but also as the condensation chamber. Interior-coated vessels have a particularly long life.

10. What is a condensate drain valve?
It is installed at the lowest point on the vessel so that the condensate can be drained on a
regular basis.

11. What is the purpose of the pressure reducer?
Pressure reducers control the desired working pressure at high control accuracy and are equipped as standard with a pressure gauge. The adjustment button is lockable so that during operation the pressure cannot be adjusted.

12. What is a water separator with filter?
Water separators with filters drain semi-automatically and comprise a mechanical filter with 20 µm and a further separation level through the centrifugal acceleration of the compressed air.

13. What is a filter pressure reducer?
Filter pressure reducers extend the advantages of the pressure reducers by semi-automatic draining before the pressure reducer.
They are equipped as standard with a pressure gauge and a replaceable filter element with 20µm (factory series) and/or 50µm (compact series). Special designs of the filter element are possible. The condensate collecting tanks of the factory series are made of metal and equipped with a level display. The sight glasses of the compact series are made of transparent all-plastic.

14. What is a mist oiler?
Mist oilers enable the removal of compressed air containing oil for all pneumatic tools lubricated with oil. A consistent oil supply, as a conditioning stage after the filter pressure reducer, is guaranteed using fine control. The oil volume supplied can be regulated using the adjustment needle.
Increase = Turn counter-clockwise. Reduction = Turn clockwise.

15. What is the intake capacity?
Theoretical output capacity: It is calculated from: stroke volume x speed.

16. What is the filling capacity?
The quantity of compressed air which a piston compressor makes available as compressed energy. The compressor manufacturer provides the specification of the filling capacity in the technical description of the device. In comparison to the intake capacity, it is the actual capacity which is available for its pneumatic tools.

17. What is the effective delivery quantity?
A standardised measuring procedure. The volume flow is measured in accordance with VDMA 4362 or ISO 1217.  

18. What is the purpose of star-delta switches?
Compressors with an engine power of 5.5 kW or greater must start up using a star-delta switch due to conditions imposed by local power plants. The star-delta switch and a solenoid valve decrease the energy consumed during the start-up phase.

19. What does the pressure content product mean?
According to the EC Directive, containers are divided into classes based on their manufacture and marking. The relevant parameter is the pressure content product. 
Pressure content product (DIP) = vessel volume (l) x max. pressure (bar)
The CE marking must be visible on each of these containers.

20. TÜV inspection dates
For stationary compressors, an internal inspection must be carried out every 5 years and a pressure test at 1.3 times the final pressure must be carried out by TÜV every 10 years.

21. TÜV/Type Inspection
Compressors with pressure vessels with a pressure content product (content [l] x pressure [bar]) from 200 to 1000, which have a ZUA number (type inspection), may be put into operation by the "qualified person" (expert). The periodic inspections, if prescribed, may also be carried out by the "competent person".
From DIP=1000, the initial commissioning must be carried out by an expert (e.g. TÜV), as must the periodic inspections.