Installation Manual Series CF (excluding encapsulated screw compressors) 23042013 Rev. A / May 2007 19 of 60
4.6.3 Admixtures, impurities
Water
Water within the lubricant can lead to pene-
tration of lubricating film. Therefore final tem-
perature should always be beyond the dew
point in so far as no water can precipitate in
oil circuit.
Dirt
Abrasive impurities, such as grinding or blast-
cleaning residues, as a rule will create profile
damages and major bearing damage. There-
fore, best-possible filtration of the lubricant is
necessary (recommended filter fineness β
25
=
75 according to DIN ISO 4572).
When using oil filters with an internal bypass
as specified for instance in the implementing
regulations of German accident prevention
codes for avoidance of excessive tempera-
tures, it must further be ensured that this is
never activated. Particular attention has to be
paid to the fact that the bypass is not even
opened in the event of a machine cold start if
the pressure loss rises through the higher
viscosity. Such an effect is particularly dan-
gerous as in such a case any previously fil-
tered-out residues would be washed into the
compressor range as well as into the bear-
ings at a great concentration together with
the oil.
Foreign material in suction air
When installed in a marine atmosphere, a
high air humidity accompanied by chlorine
(salt) or a chemical atmosphere with gas ad-
mixtures in the intake air may greatly affect
the normal properties of lubricants.
It is not possible in these cases to make any
general recommendation.
4.7 Permissible flow rates
The following values are recommended as
maximum flow rates in pipes:
Air pipe
Suction side 15.0 – 20.0 m/s
Pressure side (air only) 20.0 – 25.0 m/s
(air/oil mixture) 6.0 – 8.0 m/s
Oil pipe *)
Pressure line 1.0 – 2.5 m/s
“Free” Oil drain 0.1 – 0.2 m/s
*) The stated flow rates are valid for the usual
viscosities of 32 – 68 cSt in the normal tempera-
ture range between 40°C and 80°C
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