CSF Inox CN 2, Инструкции по установке, эксплуатации и техническому обслуживанию, Страница: 6 / 16

pag. 6
Pict. 2
Pict. 3
Va
2
2g
h
min = m
V
= m/s
The suction pipe must be as short as possible and rise as it moves towards the pump if it is sucking from
a tank (Pict.2). Always fit a bottom valve with a suction rose. If on the other hand the pump is below the
level of the liquid, the pipe should descend slightly (Pict.3). If the pump is used for transporting hot liquids,
fit expansion joints to compensate any expansion of the piping. The maximum velocity of the liquid in the
suction pipe must not be greater than 3 m/s. Velocities between 1 and 2 m/s are recommended. The suction
pipe must be designed in such a way as to prevent air from entering the pump.
For this reason, when sucking from a tank located at a lower level, the pipe must reach below the free
surface of the liquid. In order to prevent the formation of vortices and avoid the risk of sucking in air, always
keep a minimum head at the pipe inlet (h. min.) equal to at least the dynamic head plus a safety margin
of 0.1 m (Pict.2).
h min = + 0,1
In order to prevent the formation of vortices when it is not possible to observe the values of minimum
available head, it is possible to fit crosses in the piping. This system is suitable even for tanks with a
positive head.
- Avoid creating obstacles which could increase suction losses disrupting smooth fluid flow. Make sure
that there are no restrictions, sharp turns or tight elbows on the discharge line, since these increase
disturbance.
Pict. 1
YES
NO