Operating and Maintenance Manual 09/2019 – part I
Screw compressors
39
The safety valves are only intended for protection of: pressure tanks,
compressed air conduits or other neutral gases, sources of compressed air
from an excessive increase in pressure (above the limit for that type of
equipment).
The safety valves must not be used as relief devices for pressure
adjustment.
8.3.14 Radial / axial fan
To ensure long and trouble-free operation of the radial or axial fan, the following rules and
recommendations should be followed:
- Every 12 months check the valve for mechanical vibration. Max. permissible vibration force
is 2.8 mm/s (measured on the bearing cover in the motor bearing at the rotor side). The
periods between inspections may be shortened depending on a degree of fouling. It applies
to the radial impellers.
- Keep the impeller clean. Dirt deposits on the impeller may result in imbalance and its failure
(risk of fatigue cracks).
- Follow the motor manufacturer’s information concerning its keeping in operative condition
and maintenance.
- The fan air ducts must be free of foreign matters –hazards caused by the thrown out
objects.
- Do not bend blades - imbalance.
- Pay attention to unusual operation sounds.
- Any repairs must only be performed by the specialised qualified personnel.
Maintenance procedure:
- Stop the compressor and close the pressure conduit valve.
- Switch off the power supply and take measures to prevent it from being unintentionally
switched on again by unauthorised persons.
- Wait minimum 5 minutes and then open the compressor guard.
- Check that the system has been emptied by slowly unscrewing the oil filler cap (use
protective clothing) (Fig.10). The compressed air can be hot.
- Open the cover that hinders access to the fan.
- Make sure that the fan impeller is not moving.
- Do not remove the impeller to clean it.
- Clean the impeller with the cloth soaked in mild detergent solution. Clean the flow area of
the fan. Do not use any aggressive cleaning agents that may dissolve its paint. You are not
allowed to use any pressure washers or strong water jet for cleaning.
- Check thoroughly the impeller, especially the welds (it applies to the radial impellers) for
any cracks.
- Close the cover that hinders access to the fan.
- Start the compressor.
- Check the fan for correct operation.
When removal is necessary, the entire rotating unit needs to be balanced again according
to DIN ISO 1940, part 1. (it applies to the radial impellers). The axial fans used because of
light weight of their moving parts do not require to be balanced again.
Replacement or lubrication of the motor bearings must be performed in accordance with
the manufacturer’s recommendations. The permissible hours of the bearing operation to
the replacement or lubrication are presented in the table below. When any symptoms
indicating the bearing damage occur (unusual noise or increased temperatures), contact
the service immediately.
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