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Self-priming operation
At the start sufficient liquid must be available in the pump filling up the internal clearance volume and
the dead spaces, allowing the pump to build up a pressure difference.
Therefore, for pumping low viscosity fluids, a foot valve with the same or larger diameter than the
suction pipe must be installed or the pump can be installed without foot-valve but in U-line.
Note! A foot valve is not recommended when pumping high viscous liquids.
•
To remove air and gases from suction line and pump, counter pressure at the discharge side
must be reduced. In case of self-priming operation, start-up of the pump should be performed
with open and empty discharge line allowing air or gases to escape at low back pressure.
•
Another possibility in case of long lines or when a non-return valve is installed in the discharge
line, is to install a by-pass with isolating valve close to the discharge side of the pump. This valve
will be opened in case of priming and allows air or gas evacuation at low back pressure.
The bypass should be lead back to the supply tank – not to the suction port.
3.17.6.3 Isolating valves
To allow proper maintenance it is necessary to be able to isolate the pump. Isolation can
be done by installing valves in suction and discharge lines.
•
These valves must have a cylindrical
passage of the same diameter of the
piping (full bore).
(Gate or ball valves are preferable).
•
When operating the pump, the valves
must be opened completely. The
output must never be regulated by
means of closing valves in suction or
discharge pipes.
It must be regulated by changing shaft
speed or by re-routing the media over
a by-pass back to the supply tank.
3.17.6.4 Strainer
Foreign particles can seriously damage the pump. Avoid the entry of these particles by installing a
strainer.
•
When selecting the strainer attention should be given to the size of the openings so that
pressure losses are minimised. The cross-sectional area of the strainer must be three times that
of the suction pipe.
•
Install the strainer in such a way that maintenance and cleaning are possible.
•
Make sure that the pressure drop in the strainer is calculated with the right viscosity. Heat the
strainer if necessary to reduce viscosity and pressure drop.
For the maximum allowable particle size see section 3.14.
3.17.7 Secondary piping
For dimensions of connections and plugs see chapter 6.0.
3.17.7.1 Drain lines
The pump is provided with drain plugs.
Be
Ba
A.0500.751 – IM-TGBLOC/01.00 EN (10/2020)
Suction
Bb
By-pass
PIPING
Discharge
31
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