Service units

From FestoWiki - english
Jump to: navigation, search

A service unit, or even just a single module of a service unit should always be used for compressed air in industrial applications.


Service unit type MS

Compressed air preparation

Why is compressed air preparation necessary?
Dirt particles, water and chemical contamination can have highly negative effects both on the compressed air consumption and on the compressed air network.
Whereas solid dirt particles lead to mechanical abrasion, for example between the cylinder wall and the piston seal, moisture can lead to corrosion of parts.
The rust particles thus generated can in turn cause mechanical damage or can clog up the flow cross sections.
Compressed air preparation is carried out in order to provide consumers with compressed air which has three main properties

  • Quality (water content, particles, oil content)
  • Quantity (minimum and maximum cross sections)
  • Pressure (minimum and maximum pressure and precision)

Connection size

What criteria are applied when choosing the connection size of a service unit?

For service units, you must not only observe the connection size, but also the flow and control range values. If the control range is OK, the right choice of a service unit is based on the air flow rate.
Whilst oversized service units generally cause no damage, they do generate unnecessary costs.


Service units

The term service unit doesn't actually indicate which service devices are installed. The most common service devices in a service unit are the following


Quality classes for compressed air

Classification of the quality classes for compressed air according to ISO 8573-1:2010

ISO 8573


Solid particles Water Oil
Maximum number of
particles per m³
concentration [mg/m³]
Pressure dew point



[g/m³ ]

Total oil content
(liquid, aerosol and vapour)


0.1-0.5 µm 0.5-1 µm 1-5 µm
0 In accordance with specifications by the device user, stricter requirements than class 1
1 ≤ 20,000 ≤ 400 ≤10 - ≤ -70 - 0.01
2  ≤ 400,000 ≤ 6,000 ≤ 100 - ≤ -40 - 0.1
3 -  ≤90,000 -≤1,000 - ≤ -20 - 1
4 - -  ≤10,000 - ≤ +3 - 5
5 - - ≤100,000 - ≤ +7 - -
6 - - -  ≤ 5 ≤ +10 - -
7 - - - 5 - 10 - ≤ 0.5 -
8 - - - - - 0.5 - 5 -
9 - - - - - 5 - 10 -
X -   -- > 10 - > 10 > 10

Did you know?

  • How much does compressed aircost?

    On average, it costs approx. 3 cent per 1 m³.

  • How much does air weigh?

    One cubic metre of air (1000 litres) weighs 1.292 kg (DIN 1343).

  • Does Festo have a condensate collecting bowl in its product range?

    We recommend using filter silencers type LFU

  • Does the service unit have to be fitted with a manual on-off valve?

    According to EN 983 point 5.1.6, the systems must be designed so that it is possible to disconnect them completely from the energy sources and also to reduce energy in the
    system in order to prevent unexpected start-up. In pneumatic systems, this can for example be done by disconnecting the system from the energy supply and

   dissipating the pressure in the system. The suitable shut-off device, which features a pressure relief mechanism, must be lockable.

  • Does the automatic condensate drain work even if no air is consumed?

    There are only a few restrictions for the automatic condensate drain to function correctly. These are the vertical mounting position and a minimum provided flow rate at switch on moment of 125 l/min. If the flow rate lies below this value, it may be that the condensate drain, which is open in depressurised state, has not closed.

  • What is the difference between an automatic and semi-automatic condensate drain?

    The semi-automatic condensate drain opens automatically if the component is depressurised. A fully automatic condensate drain also does this. In addition, a fully automatic
    condensate drain also opens even if pressurised and when the condensate reaches a specific level.