Series MNKA bearing pedestal assembly 4
Page 11
9250-003-en
Revision 01
TM 10458
Published 06/2022
5.4 Pipelines
Before installing the pump, clean both the suction
line and supply line as well as the discharge line.
To prevent soiling or damage to the sealing sur-
faces, leave the flange covers on the flanges until
immediately before installation.
Use flange gaskets suitable for the pumped
medium.
For tightening the flange screws, observe the
screw tightening torques in
section 1.1
.
5.4.1 Nominal diameter
The operating point of a centrifugal pump is at the
intersection of the pump characteristic curve and
the piping characteristic curve, see
Figure 2
. The
pump characteristic curve is provided by the pump
manufacturer. The pipe characteristic curve is de-
termined by means of diagrams or PC programs.
Figure 2
Under no circumstances can the nominal diameter
of the pipe be determined from the nominal con-
nection diameter of the pump.
As a rough guide, the nominal pipe size can be
determined from the flow velocity.
The velocity in the suction line should not exceed
6.56 ft/s (2.0 m/s) and in the discharge line 16.4
ft/s (5.0 m/s).
The NPSH (net positive suction head) value must
also be considered when determining the nominal
suction line size. The NPSHR value required for
the pump is given in the data sheet.
The
NPSHA
present
in
the
system
should
be
at
least
1.64 ft (0.5 m) greater than the NPSHR
required for the pump. Otherwise, a drop
in pressure head, cavitation or even
pump failure will occur.
5.4.2 Nozzle loading
The pump can be nozzle loaded according to
ANSI/HI 9.6.2. For values see installation plan.
Temperature-related changes in the length of the
pipeline must be taken into account by suitable
measures, e.g. by installing expansion joints.
5.4.3 Suction line
Lay the suction lines so that they consistently rise
towards the pump. Otherwise, gas bubbles may
form which considerably narrow the suction line
cross-section. Install eccentric transition pieces
between different pipe diameters.
Do not install fittings that interfere with the flow di-
rectly upstream of the pump.
Figure 3
5.4.4 Supply line
Supply pipes should vent towards the tank and
must be laid continuously downward towards the
pump. If the pipe installations are horizontal in
front of the pump, a low point can be arranged in
front of it. From here, the pipe is then laid rising
again to the pump; the gas bubbles that form here
can escape through the pump.
Do not install fittings that interfere with the flow
directly upstream of the pump.
5.4.5 Discharge line
Do not place the shut-off valve directly above the
pump, but first provide a transition piece.
The discharge nozzle velocity of the liquid can be
reduced, if necessary.
)
m
(
A
)
s
/
m
(
Q
)
s
/
m
(
v
2
3
=
Pump characteristic
curve
Suction line
Pump suction
connection
Operating point
Pipe characteristic curve
