Brochure

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101101
The pressure taps are designed so that the velocity in the pipe aects the
static pressure measurement the least possible. To balance a possible bias in
the velocity profile, each pressure tab has four measuring holes so that the
measured pressure will be an average, see figure 6.4.
The measuring holes are drilled perpendicular in the pipe wall making them
perpendicular to the flow. The measuring holes are small and have sharp
edges to minimise the creation of vorticies in and around the holes, see
figure 6.5.
It is important that the pressure taps and the connection to the pressure
transducer are completely vented before the pressure measurement is
made. Air in the tube between the pressure tap and transducer causes er-
rors in the pressure measurement.
The pressure transducer measures the pressure at the end of the pressure
tube. The measurements are corrected for dierence in height Δz between
the center of the pressure tap and the transducer to know the pressure at
the pressure tap itself, see figure 6.4. Corrections for dierence in height are
also made between the pressure taps on the pump’s inlet and outlet side.
If the pump is mounted in a well with free surface, the dierence in height
between fluid surface and the pressure tap on the pump’s outlet side must
be corrected, see section 6.2.4.
6.2.3 Temperature
The temperature of the fluid must be known to determine its density. The
density is used for conversion between pressure and head and is found by
table look up, see the chart ”Physical properties of water” at the back of the
book.
Figure 6.5: Draft of pressure tap.
Figure 6.4: Pressure taps which average over
four measuring holes.
Pressure gauge
Venting
Dz