Speck pumpen VZ 11 B Series, Руководство по эксплуатации

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OPERATING INSTRUCTIONS
26
7.3
Cavitation: Causes and how to
avoid them.
CAUTION
In case that the suction pipe I
s
is provided with
a shut-off device (slide or similar), and the
pump should be kept running, when this shut-
off device is closed, cavitation will be caused.
Consequently parts of the pump will be de-
stroyed, in case the pump is running a longer
period.
In case mainly steam shall be delivered, which
condenses during compression, also cavitation
is caused in the pump.
In order to avoid cavitation with its conse-
quences, a small quantity of gas will be added
at suction side or through the connection for
cavitation protection, which cannot condensate
at compression:
This can be effected through
•
a ventilation device h,
•
through a pipe with jet nozzle I
G
elevated
by 300 mm or
•
through a connecting pipe (with nozzle) to
the liquid separator a.
The use of a gas ejector also avoids cavitation.
If a large amount of dirt is deposited, it should
be removed constantly. However, when the
pump is idle it empties and the pipe mentioned
above should therefore be closed before
shopping the pump. This makes it unneces-
sary to refill up to the middle of the shaft before
restarting the pump.
If the pump is operated with water the hard-
ness of the water has to be observed by all
means, as very hard water causes lime depos-
its in the pump. In such cases the required
water has to be treated (to be softened) as ring
liquid before use or the pump has to be
opened from time to time to remove the depos-
its.
8
Maintenance
Version with mechanical seals.
The mechanical seals need no maintenance.
Ball Bearings
For VZ type range grooved ball bearings with
cover disks are used.
The ball bearings need no maintenance.