DESMI PUMPING TECHNOLOGY A/S
-9-
Tagholm 1
9400 Nørresundby - Denmark
Tel.: +45 96 32 81 11
Fax +45 98 17 54 99
E-mail:
www.desmi.com
8.
DISMANTLING
Before dismantling the pump make sure that it has stopped. Empty the pump of
liquid before it is dismantled from the piping system. If the pump has been pumping
dangerous liquids you are to be aware of this and take the necessary safety
measures. If the pump has been pumping hot liquids, take great care that it is
drained before it is removed from the piping system. If cold or very hot liquids have
been pumped, the operator must be aware that it is dangerous to touch the pump
surface and he must, consequently, take the necessary safety measures.
9.
START-UP
A self-priming centrifugal pump will not function until the pump casing has been filled
with liquid.
The liquid also serves as coolant for the shaft seal. In order to protect the shaft seal
the pump must not run dry.
WARNING
For safety reasons the pump is only allowed to operate against closed discharge valve for a short
time (max. 5 minutes and at a max. temperature of 80°C for standard pumps). Otherwise there is a
risk of damage to the pump and, at worst, of a steam explosion. If the pump is not monitored, the
installation of a safety device is recommended.
9.1
STARTING
Before starting the pump check that
- the shaft rotates freely without noise
- the pump casing is filled with liquid.
Start the pump for a moment to check direction of rotation. If the direction is correct (i.e. in the
direction of the arrow), the pump may be started.
10.
SYSTEM
BALANCING
It is often difficult to calculate a manometric delivery head in advance. It is, however, decisively
important to the quantity of liquid delivered.
A considerably smaller delivery head than expected
will increase the quantity of liquid delivered, causing increased power consumption and perhaps
cavitation in pump and piping. In the pump the impeller may show signs of heavy erosion caused
by cavitation (corrosion) which may at times render an impeller unfit for use in a very short time.
Not unusually do similar erosions occur in pipe bends and valves elsewhere in the piping system.
Therefore, after start-up, it is necessary to check either the quantity of liquid delivered or the power
consumption of the pump e.g. by measuring the current intensity of the connected motor. Together
with a reading of the differential pressure the quantity of water delivered can be determined against
the characteristics of the pump.
In cases where the liquid flow of the pump has to be reduced a valve in the piping system is the
most common solution. This valve
always
has to be placed on the suction side of the pump - never
on the delivery side.
Should the pump not function as intended, please proceed according to the fault-finding list. Bear
in mind, though, that the pump was carefully checked and tested at the factory and that the
majority of faults stem from the piping system.