Mechanical Installation; Inlet Pipe - Grundfos KP Instrucciones De Instalación Y Funcionamiento

4.4 Mechanical installation

4.4.1 Piping
Do not let the pump support the pipes. Use pipe
hangers or other supports at proper intervals to
provide pipe support near the pump.
• Make sure that both the inlet and outlet pipes are
independently supported and properly aligned so that no strain
is transmitted to the pump when the flange bolts are tightened.
Use of expansion joints or vibration pads does not preclude
the need to properly support the pipes. Make sure that the
pipes are as straight as possible, so as to avoid unnecessary
bends and fittings.
• KP, KPV, KPVS pumps have 250 lb flanges which are drilled
according to the pump's service. Non-standard hardware may
be required.
• Do not apply force to pipes when making connections.

4.4.2 Inlet pipe

Select and install the inlet pipe in a manner that minimizes
pressure loss and permits sufficient liquid flow into the pump
during starting and operation. Many NPSH issues can be traced
to improper selection and installation of the inlet pipe.
Observe the following precautions when installing the inlet pipe:
• Run the inlet pipe as straight as possible to avoid unnecessary
bends and fittings. Ideally, make sure that the length is at least
ten times the pipe diameter. A short inlet pipe can be the same
diameter as the inlet port. A long pipe must be one or two
sizes larger than the inlet port, depending on the length, and
with a reducer between the pipe and the inlet port.
• Use an eccentric reducer, with the tapered side down. See fig.
7.
At no point must the diameter of the inlet pipe be
smaller than that of the pump inlet port.
• If possible, run a horizontal inlet line along an even gradient.
We recommend a gradual upward slope to the pump under
suction lift conditions, and a gradual downward slope under
positive inlet pressure conditions.
• Avoid any high points, such as pipe loops (see fig. 8), as this
may create air pockets and throttle the system or cause erratic
pumping.
• Install a gate valve in the inlet line to be able to isolate the
pump during shutdown and maintenance, and to facilitate
pump removal. Where two or more pumps are connected to
the same inlet line, install two gate valves to be able to isolate
each pump from the line.
• Always install gate valves or butterfly valves in positions that
prevent air pockets.
Do not use globe valves, particularly when NPSH is
critical.
8
• During pumping operation, the valves on the inlet line must
always be fully open.
• Install properly sized pressure gauges to enable the operator
to monitor the pump performance and determine whether the
pump conforms to the parameter of the performance curve. If
cavitation, vapor binding, or other unstable operating
situations occur, the pressure gauges will indicate wide
fluctuation in the inlet and outlet pressures.
Correct
Eccentric
reducer
Wrong
Air pocket
Concentric
reducer
Inlet pipe
Fig. 7
Correct
Air pocket
Air pocket prevention
Fig. 8
Taper is down
Wrong