Which of the following could make a liquid flowmeter measurement unstable?

A. Loose flowmeter fitting
B. Loose flowmeter wiring
C. Air in impulse line
D. Swirling flow profile
E. Flowmeter located between two reducers
F. Defective piping support
G. Oscillating flow

If you thought that all of these issues could cause a flowmeter measurement to become unstable, you would be almost correct. Depending upon the process and flow technology employed, any of these issues could cause the flow measurement to become unstable except (perhaps) Answer G, oscillating flow. In this case, it is the process that is unstable — not the flowmeter.

Additional complicating factors

The complicating factor associated with addressing flowmeter instability is the tens (if not hundreds) of potential sources of flowmeter instability to consider. The first order of business should be to determine if the instability is a process problem or a flowmeter problem. Stabilizing the process by “fixing” the flowmeter is analogous to an ostrich putting its head in the sand. It is clearly counterproductive but (unfortunately) can be politically expedient. Consider hiring an outside consultant to diagnose the problems when plant personnel cannot locate and remedy the root cause of the problem,