How do I care for the air compressor

Compressor maintenance & care in 7 steps

The Compressor maintenance should be carried out regularly so that unnecessary defects, operational failures or even accidents are avoided in advance.

In the following we therefore show how the complete Maintenance of a standard compressed air compressor in 7 easy steps is carried out.

Compressor maintenance & care in 7 steps

How do you maintain a compressed air compressor? This is a frequently asked question that is rightly asked and which reaches us regularly.

Because, like a car, you should also maintain and care for your compressor at regular intervals, whether it's commercial or private.

We have now created a simple 7-step guide including a legend of all maintenance parts with which you can care for your compressor and keep it in good working order.


1. Let the compressor warm up

Before we start with the compressed air compressor maintenance, it is recommended as a first step to let the device warm up once.

During the subsequent maintenance, all components, especially on the motor, compressor block and air lines, can be examined under the influence of heat and pressure. The oil can also be drained more easily if necessary.

2. Function test of the safety and operating elements & leak test of the compressed air lines


While our unit is just warming up and has already built up pressure, in the second step of the compressor maintenance we can now directly test the function of the safety and operating elements such as emergency stop / on / off switch, pressure relief valve and pressure reducer as well as the tightness of the compressed air lines on the compressor check.

All safety / operating components are usually located on the compressor maintenance unit (see Fig. 2).

2.1 Testing the emergency stop / on / off switch

We test the emergency stop or on / off switch (4 / Fig. 2) by simply pressing it. As soon as this has been pressed, the compressor must switch off immediately.

2.2 Test compressed air lines on the compressor

After the compressor has switched off, the compressed air lines (6 / Fig. 2) between the compressor, boiler and air extraction point can be checked for leaks.

The simple test without a measuring device can be implemented by feeling with the hand along the lines and by hearing a possible quiet hissing sound at the screwed cable connections.

The compressor should have reached its maximum pressure of 8 bar to 10 bar.

2.3 Test the function of the pressure reducer

After the leak test, we can now test the pressure reducer (1 / Fig. 2). To do this, we turn the regulator slightly counterclockwise until the working pressure on the manometer (3 / Fig. 2) drops and adapts.

Do not turn the pressure reducer all the way down, as we still need some pressure in the boiler for the next test.

2.4 Test the pressure relief valve

As soon as all lines and the function of the pressure reducer have been checked, it is the turn to test the pressure relief valve (5 / Fig. 2).

This is used for rapid manual pressure reduction in the boiler and can usually be operated by pulling a finger on a small ring. During actuation (keep pulling) the boiler pressure, which can be read on the pressure gauge, should drop relatively quickly.

3. Disconnect the compressor from pressure and power

As soon as the functionality of the emergency stop and pressure relief valve has been checked, the next step is to switch the compressor completely to zero and pressureless in order to be able to carry out further maintenance work safely and professionally.

It is sufficient to completely switch off the compressor Not to operate the on / off switch or the emergency stop. Instead, the compressor must be completely disconnected from the mains by pulling the power plug out of the socket.

In order to get the air storage tank completely pressureless, the pressure can either be released by actuating the pressure relief valve or e.g. a simple compressed air gun.

4. Drain the condensation water

Since moisture is always sucked in with the room air, condensate collects in the air tank.

Condensate, which collects in larger quantities and for a longer period of time in the boiler, can lead to faster rusting through and more frequent switching on of the compressor, as the condensate in the boiler takes away the air storage volume.

To prevent this, all compressed air compressors are equipped with a condensate drain valve (10 / Fig. 1) on the underside of the boiler.

In order to be able to drain water from the compressor, a flat container is placed under the drain tap and the tap is then opened.

So that the accumulated condensation can now drain off completely, it is advisable to tilt the compressor slightly alternately in both directions.

5. Check the oil level / change the oil

It is also very important during compressor maintenance to check the oil level or, if necessary, to carry out an oil change directly.

5.1 Check the oil level


Checking the oil level is also immensely important during the maintenance of the compressor, since too little oil in the compressor can lead to expensive consequential damage such as piston seizure or the crankshaft, bearings or connecting rods sticking.

In most cases, the oil level is checked very simply via the oil sight glass (4 / Fig. 3), which is attached to the side of the compressor. Older compressors sometimes have an oil dipstick for this, as we know it from the car.

If the oil level is too low or if the red point in the middle of the sight glass is reached or below, this should be refilled with a compressor with oil of the appropriate viscosity.

To do this, open the oil filler neck (1 / Fig. 3), insert a funnel and slowly let in enough oil until only a small air bubble is visible on the top of the sight glass or the upper mark on the dipstick has been reached.

If the compressor runs quietly and gets a little louder over time, this is mostly due to the increased mechanical friction in the piston and crankcase due to the oil level being too low.

Danger: If too much oil is filled in, this can lead to the Simmerrings leaking and the excess oil mixing with the compressed air in the boiler. As a result, there is an increased amount of oil in the compressed air until the oil drops below the maximum level again.

5.2 Change the oil

Depending on how many operating hours the compressor has already had since the last oil change (see maintenance schedule below), it may be possible to completely replace the old oil with a new one.

To carry out an oil change on the compressor, the existing compressor oil is first drained into a collecting container using the oil drain screw (2 / Fig. 3). After all the oil seems to have run off, tilt the compressor slightly again so that the last drop of oil can run off.

Then close the oil drain plug again, open the oil filler neck and fill in sufficient new oil using a funnel.

With oil-free compressors, this maintenance step of checking the oil level / changing the oil is completely omitted.

6. Clean or replace the intake air filter

One point that is easily overlooked in compressed air compressor maintenance, but should not be underestimated, is cleaning or replacing the intake air filter (s) (5 and 6 / Fig. 1).

A cleaned air filter can not only increase the intake performance and energy efficiency of the compressor, but clean air is also a decisive criterion for the service life of the air compressor.

The intake air filter is usually located at the top on the intake side of the compressor and should either be cleaned (blown out) or replaced with a new one, depending on the degree of contamination and condition.

7. Visual inspection: inspect wear parts and power lines

The last step of our compressor maintenance is the visual inspection of all important wear parts and the power lines.

If you have a belt-driven compressor, the V-belt should be checked for coarser tears, its porosity and the correct tension (not too tight and not too loose) and, if necessary, retightened or replaced.

The electrical connection cable is examined for damage and tears in the insulation as well as for loose or rusted contacts on the plug.

The boiler should also be checked for traces of rust. Is it harmless rust film or is there serious corrosion damage (risk of explosion) that requires a new compressor or the consultation of a specialist?

It is also advisable to check all directly accessible screw connections on the compressor, air lines, air extraction point and impellers and tighten them if necessary.

How often does a compressor have to be serviced? (Compressor maintenance schedule)

How often a compressor needs to be serviced depends on how intensively and regularly it is used.

This is why it makes no sense, especially in the commercial sector, to use a general time schedule such as “maintenance once a year”.

Rather, the maintenance intervals of air compressors are based on the operating hours that you have been using since the purchase or the last service.

For commercial use we have the following as a rough guide Compressor maintenance schedule created

  • Drain the condensation water in the boiler - after every day of use
  • First oil change - after approx. 100 operating hours
  • Further oil changes - every 1000 hours of operation
  • Oil level check - monthly
  • Oil Loss Control - Monthly
  • Clean Air Filter - Monthly
  • Replace air filter - every 500 hours of operation
  • Belt tension control - monthly
  • Check compressed air lines - every 1000 operating hours
  • Check electrical lines - every 1000 hours of operation

For the occasional private use is for the frequency annual compressor maintenance mostly sufficient. Except for draining the condensation, this should be done at least every 3 months.

Which compressors are subject to inspection and how often do they have to be inspected by the TÜV?

From a certain container size and pressure capacity, commercially used compressors have an increased risk of accidents due to explosions due to cracks and leaks in the compressed air tank.

Therefore, these regular TÜV tests (internal test & strength test) must be subjected.

When is a compressor subject to inspection?

From when or which compressors have to undergo a regular TÜV test, depends on their Print Volume Product (PS / V) from, which results from the Boiler volume (V) and the maximum Boiler pressure (PS) calculated.

The Compressed Air Operational Safety Ordinance (BetrSichV) specifies the Limit at 1000 PS / V firmly. Above this value, it is a compressed air system that requires monitoring, which must be checked by the TÜV at regular intervals.

Compressed air compressors with a pressure volume product of 200 - 1000 hp / V do not have to be TÜV approved but at least by a qualified person be checked in operation.

Compressed air compressors below 200 hp / V however, do not need to be checked by TÜV or a trained person.

A PS / V of 1000 results, for example, from a larger compressor with a 100 l tank and a maximum tank pressure of 10 bar.

Sample calculations:

  • 10 bar (PS) x 50l (V) = 500 PS / V - not subject to TÜV inspection
  • 8 bar (PS) x 100l (V) = 800 PS / V - not subject to TÜV inspection
  • 10 bar (PS) x 100l (V) = 1000 PS / V - subject to TÜV inspection

Accordingly, a compressor with a 50l or sometimes 100l boiler (if below 10 bar boiler pressure) does not have to go directly to the TÜV, as it usually does not reach more than 8 to 10 bar boiler pressure and the PS / V thus remains below the limit of 1000.

It should be noted, however, that even with 50l compressors, initial commissioning no longer has to be carried out by trained persons, but directly by TÜV or DEKRA (only applies for commercial purposes). This does not apply to compressors with an existing type test from the manufacturer. As before, these may be commissioned by qualified persons.

For more information see PDF from TÜV-Süd.

How often do compressors have to be checked?

According to § 15 BetrSichV, commercially used air compressors with a compressed air tank of less than 1000 PS / V must be subjected to an annual expert test.

For compressors from 1000 PS / V, however, an internal test (a.b.a. visual test) and a strength test every 10 years (container is placed under 1.3 times the test pressure) by TÜV or DEKRA must be carried out every 5 years.

To prepare for the TÜV, have the compressor serviced by professional companies

Especially before an upcoming TÜV test, it is often advisable to have the compressor serviced by a professional company.

In addition to the professional measuring devices, they also have the experience and usually know exactly what to do so that the compressor (regardless of whether it is a screw compressor or piston compressor) passes the TÜV test without complaints and is not temporarily shut down.

Note: This is just a guide with tips on compressor maintenance and care. The owners of assume no liability / responsibility for possible accidents caused by electric shock or pressure explosions.