B-3
Appendix B
Process Conditions Process conditions and loop elements must be considered during site
selection to ensure an accurate, noise-free output signal. Avoid
placement near pumps (especially positive displacement pumps) or flow
variations may appear in the output signal.
Also, keep slurries as homogeneous as possible to prevent damage to
the flowtube electrodes and liner. Homogeneity can often be achieved by
locating the flowtube five straight pipe diameters downstream of loop
pumps, with additives upstream of the pumps.
Finally, design the process loop conditions to ensure that the flowtube
always remains full, with no entrapped air.
Adequate Space Allow space for the flowtube, bypass piping, and equipment
maneuverability during installation and removal. Note that integrally
mounted transmitters require more space at the flowtube site.
Earth Ground Specification accuracy and safety considerations require
flowtube grounding.
Low-Noise Environment Although a pulsed dc coil design reduces flowtube susceptibility to
extraneous noise, some environments are more suitable than others.
Avoid a close proximity to devices that may produce high intensity
electromagnetic and electrostatic fields. Such devices include electric
welding equipment, large electric motors and transformers, motor
devices or controls, and communication transmitters.
Conductivity Process fluid conductivity should be 5 microsiemens/cm (5 micromhos/
cm) or greater. For low conductivity fluids, 5–20 micromhos/cm, cable
length should be less than 25 feet and unshielded cable ends should
be maintained.
8732-0044C
Flow
FIGURE B-2.
Typical Bypass Piping Configuration.
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