2.4 Other installation considerations
Numerous external factors can affect the meter's successful operation. To ensure that your
system works correctly, consider the factors covered in this section when designing your
installation.
2.4.1 Boundary effect
Boundary effect refers to the distortion in the wave forms in the process fluid that are
caused by reflections from the pipe wall. If the pipe wall is within the meter's effective
measurement region, the boundary effect produces measurement inaccuracy.
Figure 2-3: Region of measurement boundary or sensitivity (plan view)
A. Sensitive, or effective, region
The factory calibration compensates for the boundary effect. The meter can be calibrated
for free stream, 2 in (51 mm), 2.5 in (64 mm), or 3 in (76 mm) pipe. If the meter is installed
in a pipe that does not match the calibration size, the compensation will be inaccurate,
and process measurement will be inaccurate.
Verify that the meter was calibrated for the pipe size you plan to use.
2.4.2
Flow rates
Maintain constant flow rates and velocities that are within the limits specified for the
meter. The fluid flow provides a steady heat flow into the meter installation, and the flow
rate influences the self-cleaning of the meter tines, the dissipation of bubbles, and the
solid contaminants around the meter.
If you install the meter in a bypass configuration (such as in a flow-through chamber), use
a pressure drop across an orifice plate in the main process pipe, a pitot scoop
arrangement, or a sample pump to maintain flow. When using a sample pump, place the
pump upstream from the meter.
2.4.3
Entrained gas
Entrained gas, or gas pockets, can disrupt the measurement of a fluid. A brief disruption in
the signal caused by transient gas pockets can be corrected in the meter configuration,
Planning
Installation Manual
May 2019 MMI-20020989
10 Micro Motion Fork Density Meter
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