Flowserve MN User Manual
Page 21
MN USER INSTRUCTIONS ENGLISH 71569189 11/04
Page 21 of 49
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4.6.2.1 Suction piping guidelines
a) The inlet pipe should be one or two sizes larger
than the pump inlet bore and pipe bends should
be as large a radius as possible.
b) Pipework reducers should have a maximum total
angle of divergence of 15 degrees.
c) On suction lift the piping should be inclined up
towards the pump inlet with eccentric reducers
incorporated to prevent air locks.
d) On positive suction, the inlet piping must have a
constant fall towards the pump.
e) Flow should enter the pump suction with uniform
flow, to minimize noise and wear. This is
particularly important on large or high-speed
pumps that should have a minimum of four
diameters of straight pipe on the pump suction
between the elbow and inlet flange.
f) Inlet strainers, when used, should have a net
‘free area' of at least three times the inlet pipe
area.
g) Do not install elbows at an angle other than
perpendicular to the shaft axis. Elbows parallel
to the shaft axis will cause uneven flow.
h) Except in unusual circumstances strainers are
not recommended in inlet piping. If considerable
foreign matter is expected a screen installed at
the entrance to the wet well is preferable.
i) Fitting an isolation valve will allow easier
maintenance.
j) Never throttle pump on suction side and never
place a valve directly on the pump inlet nozzle.
4.6.3 Discharge piping
A check valve and a gate valve are normally installed
in the discharge line. The check valve is normally
placed between the pump and the gate valve to
protect the pump from any excessive back pressure
and reverse rotation that may be caused by water
running back through the pump casing during a driver
or power failure. Any reverse flow through the pump
or excessive back pressure should be kept to its
absolute minimum. The check valve will also prevent
suspended solids from accumulating in the casing
and will increase wearing ring life.
•
Pipework reducers should have a maximum total
angle of divergence of 9 degrees
•
Fitting an isolation valve will allow easier
maintenance
•
A compound pressure gauge should be
connected to the suction and a pressure gauge to
the discharge side of each pump. Mount the
gauges at a convenient location as they are
necessary for any adequate check on the pump
performance
4.6.4 Auxiliary piping
4.6.4.1 Drains
Pipe pump casing drains and gland leakage to a
convenient disposal point.
4.6.4.2 Pumps fitted with gland packing
When suction pressure is below ambient pressure, it
is necessary to feed the gland packing with liquid to
provide lubrication and prevent the ingress of air.
This is normally achieved with a supply from the
pump discharge volute to the stuffing box.
If the pumped liquid is dirty and cannot be used for
sealing, a separate clean compatible liquid supply to
the gland at 1 bar (15 psi) above the suction pressure
is recommended.
4.6.4.3 Pumps fitted with mechanical seals
Single seals requiring re-circulation will normally be
provided with the auxiliary piping from pump casing
already fitted.
Special seals may require different auxiliary piping to
that described above. Consult seal User Instructions
and/or Flowserve, if unsure of correct method or
arrangement.
For pumping hot liquids, to avoid seal damage, it is
recommended that any external flush/cooling supply
be continued after stopping the pump.
4.6.5 Final checks
Check the tightness of all bolts in the suction and
discharge pipework. Check also the tightness of all
foundation bolts.
4.7 Electrical connections
Electrical connections must be made
by a qualified Electrician in accordance with relevant
local national and international regulations.
It is important to be aware of the EUROPEAN
DIRECTIVE on potentially explosive areas where
compliance with IEC60079-14 is an additional
requirement for making electrical connections.
It is important to be aware of the EUROPEAN
DIRECTIVE on electromagnetic compatibility when
wiring up and installing equipment on site. Attention
must be paid to ensure that the techniques used
during wiring/installation do not increase
electromagnetic emissions or decrease the
electromagnetic immunity of the equipment, wiring or