4. 5. 2. Overloading of driver
Possible cause Remedy
1. Pump discharge pressure is lower than specified at the
design stage, and in the confirmation of order (check
figures on the pump rating plate).
Partially close the isolating valve in the discharge line until the
pump discharge pressure corresponds with the figure on the
rating plate. If the driver is permanently overloaded, decrease
the driver speed if possible, or trim the impellers after having
previously consulted us.
2. The pump is pumping a fluid of higher S. G than specified
in confirmation of order. (If the temperature of a fluid
pumped, is lower than specified, this will result in a higher
S.G.).
If the specified S.G. and temperature cannot be attained, but
operating condition permit, the discharge valve can be throttled
to the point where the driver is no longer overloaded; or one or
more impellers and diffusers can be removed, or the impellers
can be trimmed. If none of the above measures are practicable,
a more powerful driver should be installed. Please consult us
first, stating exact operating conditions.
3. The by-pass non-return valve does not close when pump
is operating at full capacity.
Renew worn components. If this does not cure the trouble,
please consult us.
4. 5. 3. Excessive discharge pressure
Possible cause Remedy
1. Excessive speed. Check speed precisely. If it is not possible to decrease the
speed, one or more impellers and their diffusers should be
removed, or the outlet tips of the impeller vanes should be cut
back. Please consult us first.
2. The S.G. of the fluid pumped is too high (e.g. the
temperature of the fluid Is lower than specified).
If the pump must operate for prolonged periods under these
conditions, the measures outlined in 1. above should be taken.
3. The suction pressure is too high (on pumps operating with
positive suction head).
Check suction pressure. If no corrective steps can be taken on
the installation, the measures outline in 1. above should be
considered.
4. 5. 4. Pump leaks (other than at stuffing boxes)
Possible cause Remedy
1. The tiebolts are not tightened sufficiently. Shut down the pump, release the internal pressure, and tighten
the nuts on the tiebolts evenly after the pump has cooled down
completely.
2. Gasket or metal-to-metal sealing faces damaged. If the leakage cannot be cured by tightening the tiebolts, new
gaskets should be inserted or the metal mating faces should be
touched up (fig.22).
3. The fluid pumped is subject to sudden and violent
temperature fluctuation.
The pump may leak if the temperature of the fluid drops suddenly.
Wait until the normal operating temperature is restored. If the
leakage does not cease of its own accord, this may mean that the
gaskets or sealing faces are damaged.
If the leakage cannot be cured by tightening the tiebolts, proceed
as described under 2. above.
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