Wilo SCPV Installation And Operating Instructions Manual page 17

Alignment Tolerances:
Pump Speed Angular
Alignment
A<1000 rpm 0.15 mm TIR
B 1000 rpm
0.1 mm TIR
to 1800 rpm
C 1800 rpm
0.1 mm TIR
to 3000 rpm
7.2.4 P i p e work
No stress must be imposed on the pump casing by
the pipe work; neither by the weight of the pipes
nor by the tightening of badly fitting pipes (Figure
6). All pipe worked attached to the pump must be
fully supported and the mating faces of the pipe
flanges must be parallel and all bolt holes coinciding
with each other. (See table of maximum forces on
flanges) It is important, therefore, that alignment
of the pump and motor
should be re-checked after the pipes are finally
fitted. Resetting or supporting the pipes must
correct any deviation in the alignment.
Avoid stress on the pump casing
a: Pump flange;
b: Pipe work
For difficult pumping on the suction side, to stabilize
the flow, a pipe length 15 times the diameter of
the suction branch should be installed before the
suction branch.
The flow rate in the suction line or inflow line must
not exceed 2 - 3 m/s.
Pipe velocity may need to be reduced further to
satisfy pump NPSH requirements and to control
suction pipe losses
7.2.5 Suction line (Refer Figure: 4&5)
The suction pipe should be as short as possible. An
arrangement of suction pipe work, which is
common to two or more pumps operating on
suction lift, is not recommended. If such an
arrangement is unavoidable, any points of possible
air ingress, such as valve and glands, should be
liquid sealed and isolating valves should be fitted at
appropriate points.
The diameter of the suction pipe required, depends
upon its length and bears no fixed relation to the
diameter of the suction branch of the pump. The
Installation and operating instructions Wilo – SCPV pumps
Radial
Alignment
0.15 mm TIR
0.15 mm TIR
0.1 mm TIR
size of the pipe must be such that friction losses are kept
to a minimum. For example a long suction pipe (or one with
numerous bends) which passes a given quantity of liquid
must be of larger bore than a short straight one passing
the same quantity of liquid. When the suction pipe is
increased to a size larger than the bore of the pump
suction branch, the form of taper pipe used must not allow
the formation of air pockets.
To avoid the formation of air pockets, the installation of
the suction pipe work must be arranged under the
following conditions:
With as few bends as possible.
It must be completely airtight.
There must be a gradual rise towards the pump.
The inlet of the suction pipe must lie well below the lowest
possible water level and it must be fitted with the strainer.
The strainer must be clear off the bottom and sides of well
or sump so that deposits of sediment or grit are not drawn
into the pump. The strainer must be of rugged
construction with holes in the side, suitable for type of
liquid to be passed. For clean liquid the cumulative area of
these holes must not be less than twice the area of the
bore of the pump suction branch.
Where the liquid is known to contain a high percentage of
solids, the cumulative area of
greater; it may even be necessary to provide special
apparatus, such as travelling screens, to ensure that the
pump is kept free of solid foreign matter.
As these pumps are generally expected to operate on
positive head, foot valve is not necessary. However, at site,
if liquid level falls below the minimum water level
mentioned in the drawing, the pump should not be started.
Layout of pump installation
1) Eccentric reducer (suction) or concentric reducer
(discharge)
2) Isolating valve
3) Suction line
4) Bend
5) Foot valve with strainer
6) Isolating valve
7) Regulating valve
8) Pipe Support
the holes must be much
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