in the case of a risk of floo-
ding.
When the smaller units, posi-
tioned on single-piece, metal
baseplates, are placed directly
on a floor surface, only the
anchor bolts need to be imbed-
ded in concrete
(fig. 2)
.
For the larger units and, in particular for those moun-
ted on a
welded steel-section baseplate
, it is
necessary to provide for a foundation base in reinfor-
ced concrete to withstand the load and strain derived
from the unit and from the pipes, to maintain the
ali-
gnment
and to avoid vibration of the unit (see also
sections 6.4.3, 6.4.4.
).
Position the unit and provide support for the basepla-
te with separators or wedges to obtain proper hori-
zontal alignment with a spirit-level, leaving between
the baseplate and the rough scarfed surface of the
foundation a clearance of 1-2 inches (25÷50mm) for
the grouting.
With the welded metal
baseplates, it is sufficient
for the grout to rise a little
above the lower part to
allow for imbedding of the
anchor bolts and to provide
a stable base with uniform
distribution of the load over
the support surface of the
baseplate
(fig. 3)
.
Tighten uniformly all anchor bolts when the grout has
become solid (normally at least 48 hours after pou-
ring).
6.4.2. Pipe-work
The inside diameter of pipes depends on the delivery
required.
The diameter should be determined so that the liquid
flow velocity will not exceed 1.5 m/sec in the suction
pipe and 3 m/sec in the delivery pipe. In any case,
pipe diameters must never be smaller than the dia-
meter of pump connection ports.
Minimum internal diameters (DN) of suction pipes
for different capacities (Q) are indicated in the table
below.
DN
mm
50 65 80 100 125 150 200 250 300
Q max m
3
/h 10,5 19 28,8 45 75 108 215 350 508
The
suction pipe
must be perfectly air-tight and lead
upwards so as to
avoid formation of air po-ckets.
If a suction gate valve is mounted, the handwheel
must be positioned horizontally.
Use an eccentric transition piece to join the suction
connection with a horizontal pipe of larger diameter
(fig. 4)
.
For suction operation, a
foot valve with strainer
(constantly immersed) must be fitted.
For suction from a storage tank, a
check valve
must
be fitted. For operation with positive suction head, a
gate valve must be fitted.
Follow local specifications if network pressure is to be
increased.
Fit a gate valve into the
delivery pipe
to adjust deli-
very, head and absorbed power. Install a pressure
gauge.
When the geodetic head at delivery is above 15 m,
insert a check valve between the pump and gate valve
to protect the pump against water hammering.
6.4.3. Connecting the pipe-work
ATTENTION: The pipes connected to the pump
should be secured to rest clamps so that they do
not transmit stress, strain or vibrations to the
pump.
Pipes must be anchored on their own supports
(fig. 4)
.
Pipes must be modified if they do not correspond exac-
tly with th eposition of connections to avoid transmis-
sion of stress to the pump.
Position correctly any compensators (flexible expansion
joints) for absorption of expansion or vibration.
ATTENTION: forces and moments acting on the
pump flanges due to pipe loads may cause misa-
lignment of pump and driver shafts, deformation
and overstressing of pump ca-sing, or overstres-
sing of the fixing bolts between pump and base-
plate.
For connection of pipes to the flanged connection
ports, use standardized, circular counter-flanges
(type PN 10 or PN 16 up to DN 150).
During installation, make sure the gaskets between
flanges do not protrude inside pipes.
Make sure the inside of the pipe is clean before con-
nection.
In a new pipeline (especially when a suction strainer is
not fitted), insert a conical-type temporary strainer on
the suction side of the pump to prevent solids (e.g.
welding slags and scale) from entering the pump. It is
advisable to use a strainer with 20-12,5 mesh (number
of openings per linear inch) and a free area at least
three times greater than the pipe inlet area
(fig. 5)
.
Fig. 3 Foundation for unit mounted on welded,
steel-section baseplate.
4.93.038/1
4.93.038
Fig. 5 Conical-type temporary
strainer on the suction side.
pump
4.93.037
c
b
a
d
4.93.040
Avoid formation of air pockets in suction pipe:
a) eccentric transition piece;
b) gate valve with horizontal handwheel;
c) pipe leading upwards.
Avoid trasmission of stress to the pump:
d) supports and anchoring of pipes.
Fig. 4 Connection of pipes.
Page 14 / 88
N, N4 Rev. 13 - Operating Instructions
GB
Fig. 2 Foundation for unit mounted on single-piece,
channel-steel baseplate.
4.93.038/1
4.93.038
IST N_N4 09_2018_Rev13_MXS 11_03con gall 10/09/18 10:52 Pagina 14