ENGLISH
18
9.2 Minimum inlet pressure ( Z1 )
To have good performances of the pump avoiding
cavitation phenomenon it is necessary to calculate the
suction lift Z1.
To determine the suction level Z1, the following
formula must be applied:
Z1= pb – rqd. N.P.S.H – Hr – correct pV– Hs
where:
Z1 =
difference in level in metres between the
intake mouth of the pump and the free
surface of the liquid to be pumped.
pb =
barometric pressure in mcw of the place of
installation.( chart 1, pag. 94 )
NPSH =
net load at intake of the place of work.
Hr =
load loss in metres on the whole intake
duct.
pV =
vapour tension in metres of the liquid in
relation to the temperature expressed in
°C. ( chart 2, pag. 95 )
Hs =
safety margin = minimum 0.5 metres head.
If the calculated “Z1” is positive, the pump can
operate at a suction lift of maximum “Z1” metres head.
If the calculated “Z1” is negative, than the pump has
to be fitted with a positive lift of at least “Z1” mt.
Ex. : installation at sea level
and fluid at 20°C
required N.P.S.H: 3,25 m
pb :
10,33 mcw ( chart 1, pag. 94 )
Hr :
2,04 m.
t :
20°C
pV :
0,22 m. ( chart 2, pag. 95 )
Z1 : 10,33 – 3,25 – 2,04 – 0,22 – 0,5 = 4,32 approx.
This means that the pump can operate at a suction lift
of maximum 4,32 metres head.
9.3 Electrical connections
ATTENTION!!
ALWAYS OBSERVE THE SAFETY
REGULATIONS!!
Electrical installation must be carried out by an
authorised, skilled electrician who assumes all
responsability.
THE SYSTEM MUST BE
CORRECTLY AND SAFELY
EARTHED!!
Scrupulously follow the wiring diagrams inside the
terminal board box and those on table C, pag. 93.
−
Ensure that the mains voltage is the same as that
shown on the motor data plate.
−
The pumps must always be connected to an
external switch.
−
Three-phase motors must be protected with an
automatic switch (e.g. circuit breaker) calibrated at
the values shown on the data plate of the
electropump.
−
In the case of three-phase motors with star-delta
start, ensure that the switch-over time from star to
delta is as short as possible (see table B, pag. 92 ).
In
NKV
elecropumps the terminal
board may face in four different
positions:
slacken and remove the four
retaining screws between the motor
flange and the support. Turn the motor
into the desired position and replace the
screws.
9.4 Starting
Before starting the pump and the
suction pipe have to be properly
primed pump and pipe have to be fully
filled with clean water.
Starting
NKV
In accordance with accident-prevention
regulations, the pump must be run only
if the coupling (where provided) is
suitably protected. So the pump must be
started only after having checked that
the coupling protections are correctly
fitted
.
Fig. 4
pV
NPSH
pb
Hr
Z1
Содержание KVC
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