Answer / carl_ellis

These remarks refer to the use or non-use of a coriolis mass
flow meter.

A coriolis mass flow meter should not be used

- where tight shutoff valve(s) cannot be installed upstream
and downstream for the purpose of stopping all flow so that
zeroing the coriolis flow meter can be accomplished (turning
off power to the pump is NOT the same as shutting off the
flow with a ball valve). Otherwise zero shift will plague
the operation.

- in a batch operation where the meter starts empty, then
fills, and at the end might run partially filled, unless
appropriate piping is implemented to keep the Coriolis flow
meter filled with fluid all the time.

- with suspended solids in a liquid medium that are abrasive
[abrasives erode the thin tube(s)]. Reducing the flow
velocity tends to reduce abrasion and erosion. A Coriolis
tube will quickly fail when it carries suspended solids like
sand. Unless of course, frequent replacement is just the
cost of doing business.

- with a corrosive medium that will corrode the flow tube

- with medium that is above the manufacturer's stated
process medium temperature (burns up the electronics)

- with a two phase media (liquids and gas or liquids that
will flash to vapor at the operating pressures and temperatures)

- with a medium that tends to solidify (Coriolis tubes are
very thin, very light and don't like to be brush cleaned)
unless periodic solvent cleaning is feasible.

- with a medium that tends to coat the tube, unless the
required solvent or mechanical cleaning is feasible.

- where the flow tube is subject to mechanical vibration

- when the meter is mounted where the flow is vertical down

- when the meter is mounted in horizontal piping at a high
point where gas/air can be trapped at a high point

- where the pressure drop across the flowmeter is higher
than the process can tolerate

- when the location is too close to another coriolis meter;
where each meter can be affected by crosstalk vibrations
from the other coriolis meter.

- hazardous or classified zones where the Coriolis' power
requirements exclude it from meeting hazardous area approval.

- for flow measurement requiring pipe sizes larger than
commercial coriolis meters (10 or 12" in 2014)

Carl Ellis
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