SPERONI CS Serie Instrucciones De Uso página 11

h
pv
is the vapour pressure of the liquid at the operating
temperature, expressed in metres of liquid. hpv is
the quotient between the vapour pressure and the
specific weight of the liquid.
0.5
is a margin of safety.
From the above relation it can be gathered that the
maximum permissible suction lift in an installation
depends on the value of the atmospheric pressure
(i.e. the height above sea level of the installation) and
the liquid temperature. To facilitate the user's task,
tables are provided which - the datum being water
at 4°C and at sea level - indicate the decrease in the
hydraulic pressure head as a function of the height
above sea level and the suction losses as a function
of the temperature.
Water
temperature (°C)
20
40
60
80
90
110
120
Height above
sea level (m)
500
1000
1500
2000
2500
3000
Suction
loss (m)
0,2
0,7
2,0
5,0
7,4
15,4
21,5
Suction losses
in m.
0,55
1,1
1,65
2,2
2,75
3,3
3
9
The head losses can be read from the diagram shown
in our catalogue, and in order to reduce them to a
minimum - mainly where suction is remarkable (over
4-5 metres) or when operating at the highest flow
rates - it is advisable to use a section pipe larger than
the pump inlet. In all cases it is advisable that the
pump be installed as close as possible to the source
of the pumped liquid.
fig. 1 - Pump installation
A
Right
• Eccentric reducer
• Positive inclination
• Good immersion
• Ample bends
• Suction pipe dia.≥ pump inlet
• Check valve at the delivery
B
Wrong
Wrong
• Reducer and negative
• Reducer and negative inclination
inclination
generate air locks
generate air locks
• Scanty immersion=vortex
• Scanty immersion=vortex
and whirlpools
and whirlpools
• Sharp bends
• Sharp bends
• Narrow piping
• Narrow piping