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3.4.5 Auxiliary pipes
Drains
Install the drain pipes from the pump casing and
stuffing boxes to a convenient disposal point.
Flushing pipes
• Pumps fitted with stuffing boxes
When the inlet pressure is below the ambient
pressure, supply the stuffing boxes with liquid to
provide lubrication and prevent the ingress of air.
This is normally achieved via a flushing pipe from the
outlet side to the stuffing box. You can fit a control
valve or orifice plate in the flushing pipe to control
the pressure to the stuffing box.
If the pumped liquid is dirty and cannot be used for
flushing the packing rings, we recommend a
separate clean, compatible liquid supply to the
stuffing box at 1 bar (15 psi) above the inlet
pressure.
• Pumps fitted with mechanical seals
Seals requiring recirculation will normally be
provided with a flushing pipe from the pump casing.
3.4.6 Measuring instruments
To ensure continuous monitoring of operation, we
recommend that you install pressure gauges on the
pump inlet and outlet flanges. The pressure gauge
on the inlet side must be capable of measuring
vacuum. The pressure tappings must only be opened
for test purposes. The measuring range of the outlet
side pressure gauge must be minimum 20 % above
the maximum pump outlet pressure.
When measuring with pressure gauges on the pump
flanges, note that a pressure gauge does not register
dynamic pressure (velocity pressure). The diameters
of the inlet and outlet flanges are different, and this
results in different flow velocities in the two flanges.
Consequently, the pressure gauge on the outlet
flange will not show the pressure stated in the
technical documentation, but a value which may be
lower.
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