DESMI Pumping Technology A/S 9
Tagholm 1
9400 Nørresundby –Dänemark
Tlf. nr.: +45 96 32 81 11
Fax +45 98 17 54 99
E-mail: desmi@desmi.com www.desmi.com
8. START-UP
A self-priming centrifugal pump will not function until the pump casing
has been filled with liquid. Remove the plug at the top of
the pump casing andfill the pump with cold liquid. Fit the
plug and the pump is ready for service.The liquid also
serves as coolant for the shaft seal. Consequently, the
pump must in no circumstances be started before it has
been primed with liquid. Furthermore, the pump must
never run dry.
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.
The pump is equipped with a relief valve, which opens at a pre-set pressure. Be careful: If
the valve opens, the escaping liquid will most likely be hot. The relief valve must in NO
circumstances be removed or re-adjusted !
As regards maintenance of the relief valve - see paragraph 10.
8.1 STARTING
Before starting the pump check that
- the shaft rotates freely without jarring sounds.
- the pump casing is filled with liquid.
Start the pump for a moment to check the direction of rotation. If the direction is correct (i.e.
in the direction of the arrow), the pump may be started.
9. 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.
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.
