Which of the following orientations can be used to install a Coriolis mass flowmeter to measure the mass flow of a liquid in a horizontal pipe?
A. U-tube down
B. Inverted U-tube
C. U-tube horizontal (parallel to grade)
D. Flag position
Coriolis mass flowmeters in liquid service must be completely full of liquid to measure accurately. The inverted U-tube orientation (Answer B) could accumulate gas and should not be used for liquid applications.
The flag position (Answer D) could be acceptable but would entail modification of the upstream and downstream piping to ensure that the flowmeter is full of liquid. Few Coriolis mass flowmeters are mounted horizontally (Answer C), so mounting the flowmeter with its U-tube down (Answer A) would be the practical answer.
Additional complicating factors
Not all Coriolis mass flowmeters have U-tube geometry, and some of these geometries can allow gas to accumulate in the flowmeter.
For example, a straight single-tube Coriolis mass flowmeter mounted horizontally between rising upstream piping and falling downstream piping can effectively create and inverted U-tube that can accumulate gas in the flowmeter.
Conversely, a single path self-filling and self-draining Coriolis mass flowmeter that forms a loop, jumps up and then forms another loop must be installed in the horizontal plane (Answer C) to remove all gas from the system because any other orientation can allow gas to accumulate in the flowmeter.
David W. Spitzer is a principal at Spitzer and Boyes, LLC, which offers engineering, focused market research, writing/editing white papers, strategic marketing consulting, distribution consulting, seminars and expert witness services for manufacturing and automation companies. Spitzer has written more than 400 technical articles and 10 books about flow measurement, instrumentation and process control. He can be reached at 845-623-1830 or via spitzerandboyes.com.
