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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