Piusi EX50 Manual Para El Uso Y El Mantenimiento página 28

Installation, use and maintenance
10.2 NOTES ON SUCTION AND DELIVERY LINES
DELIVERY
The selection of the pump model must be made taking into account the characteristics of the system.
The combination OF: the length of the pipe, the diameter of the pipe, as well as the accessories in-
stalled, could create back pressure that are greater than the maximum predicted pressure, thereby
causing the pump's electronic controls to intervene and reducing the dispensed flow considerably.
In these cases, to guarantee correct operation of the pump, it is necessary to reduce the resistance of
the system using pipes that are shorter or that have a greater diameter, as well as line accessories with
smaller resistances (e.g. an automatic dispensing nozzle with greater flow rate capacity).
SUCTION
Self-priming pumps are characterized by excellent suction capacity.
During the start-up phase, when the suction pipe is empty and the pump is wet with the fluid, the elec-
tric pump unit is able to suck liquid from a maximum vertical distance of 2m.
It is important to note that it could take up to 1 minute for the pump to prime and that the presence of
an automatic dispensing nozzle on the delivery side will prevent the air trapped during the installation
from being released and, therefore, the correct priming of the pump. For this reason, it is always advis-
able to prime the pump without an automatic delivery nozzle, verifying the proper wetting of the pump.
Always install a foot valve to prevent the suction pipe from being emptied and to keep the pump wet
at all times. In this way, the pump will always start up immediately the next times it is used. When the
system is in operation, the pump can operate with back pressures of up to 0.5 bars on the suction inlet;
beyond this point, the pump may begin to cavitate resulting in a drop of the flow rate and an increase
in the noise levels of the system.
In light of this, it is important to guarantee small back pressures on the suction side, by using short pipes
with diameters that are equal to or larger than those recommended, reducing bends to a minimum, and
using filters with a large cross-section and foot valves with minimum possible resistance on the suction
side. It is very important to keep the suction filters clean because, when they become clogged, they
increase the resistance of the system.
The vertical distance between the pump and the fluid must be kept as short as possible, and it must fall within
the 2m maximum required for priming. If the distance is greater, a foot valve must be installed to allow the
suction pipes to fill up and the diameter pipes must be larger. It is however recommended that pump not be
installed if the vertical distance is greater than 3m.
WARNING
28 /132
If the suction tank is higher than the pump, an anti-siphon valve should be
installed to prevent accidental diesel fuel leaks. Dimension the installa-
tion in order to control the back pressures due to water hammering
It is a good system practice to install vacuum and air pressure gauges
right at the inlets and outlets of the pump, which allow verification that
operating conditions are within anticipated limits. To prevent the suction
pipes from being emptied when the pump stops, a foot valve should be
installed.
THE INSTALLER IS RECOMMENDED TO INSTALL A SUCTION FILTER.
M0217E