Inlet Circuit - Bertolini LIGHT DUTY Serie Manual Del Usuario

4.3 INLET CIRCUIT

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The inlet circuit must be built-up correctly sized in order to prevent the cavitation phenomenon that
occurs when the inlet pressure drops below a specific value. Cavitation damages the pump com-
ponents. To size-up the inlet circuit refer to the "information on technical installation" of the Master
product catalogue
following instructions. In general:
- The inlet pipelines must be straight as much as possible, reducing curves, elbows and rough
fluctuations of section.
- Do not use oil-pressure pipe fittings, 90° elbows, fittings with multiple ways, wing nuts etc.
- Do not use foot or one-way valves.
- Use inlet filter rated at 2.5 times the rated flow of the pump
- The diameter of the filter pipes must not be smaller than the diameter of the pump inlet
pipes.
In any case always check the pressure does not drop below -0,2 bar, using a pressure
switch/pressure gauge installed in the suction pipe fitting of the pump.
Furthermore make sure that:
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The inlet pressure of the pump should never exceed 5 bar.
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Filter with a filtering degree between 50 and 80 mesh must be installed. The presence of the filter
leads to suction loss that reduces the height from which the pump can suck. That is why it is im-
portant to fit a filter of sized nominal flow rate in order to ensure that this phenomenon is not too
excessive. We recommend to fit a filter rated at least 2.5 times the rated flow of the pump.

The filter must be installed as close as possible to the pump in an easily accessible position, and
must be inspected before each pump starting.

In case of inlet in pressure through a centrifugal pump, make sure the provided flow rate is at least
1.5 times more than the pump flow rate.

The tank must be rated at least 4 times the rated flow of the pump.

The pump inlet pipes must be located close to the tank bottom, water head of at least 200 mm, to
prevent the formations of siphons.

The suction area must be protected from turbulence created by the inlet pipe of the tank, and from
the return pipelines, through special bulkheads closed on the bottom.

We suggest to carry out the part of pipeline directly next to the pump with flexible hoses, suitable
to isolate the rest of the system from the vibrations caused by the pump-engine/motor unit.

Only use stiff or flexible anti-crushing hoses.

Do not install devices for detergent sucking in the inlet circuit of the pump.

The inlet line, before being connected to the pump, should be perfectly clean inside.
In case of application with electric motors the system must be provided with sensors to protect the
pump from the problems resulting from possible water overheating or poor suction.

Install a thermostat inside the tank indicating too high temperature and a level control device in-
dicating lack of water in the tank; in case of release, these sensors stop the motor.

Next to the inlet circuit install a Pressure switch, able to stop the engine/motor when the inlet
pressure decreases below the value of incipient cavitation.
.
To prevent cavitation it is necessary to limit the suction losses according to the
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