David W. Spitzer
David W. Spitzer

What piping orientations are acceptable for flowmeters to measure the flow of water with 10 percent solids?  
A.    Flow up
B.    Flow down
C.    Flow horizontal
D.    All of the above

Commentary
If the solids remain homogeneously mixed in the water, any orientation within the limits of the flowmeter technology would be possible. Answer D would appear to be correct.  
    
However, solids and water are generally not miscible, so settling of the solids could occur in horizontal piping upstream of the flowmeter.  This can affect flowmeter performance because the liquid entering the flowmeter would not be homogeneous.  More catastrophically, high solids concentrations at the bottom of the pipe entering the flowmeter can effectively plug some flowmeters.  Answer C is not necessarily correct. 
    
Locating the flowmeter in a vertical pipe flowing upward mitigates most of the potential settling problem encountered in horizontal pipe and reasonably ensures that the flow is homogeneous. Answer A appears to be correct. 
    
Locating the flowmeter in a vertical pipe flowing downward can result in a stream of solids leaving the bottom of a horizontal pipe and falling onto the flowmeter.  This potential non-homogeneity will cause Answer B to not necessarily be correct. 

Additional Complicating Factors
For flow up in a vertical pipe, there is the possibility that extreme settling upstream of the vertical pipe could cause the liquid entering the flowmeter to be non-homogeneous.  In general, slurry flow measurement applications should be engineered carefully on an individual basis. 

David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes, LLC offering engineering, seminars, strategic marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies. He has more than 35 years of experience and has written over 10 books and 250 articles about flow measurement, instrumentation and process control.

Mr. Spitzer can be reached at 845 623-1830 or 
www.spitzerandboyes.com. Click on the “Products” tab to find his “Consumer Guides” to various flow and level measurement technologies.