Flow Control, Flow Control February 2019

Application Corner By David W Spitzer Flowmeter slippage Avoiding the avoidable E very now and then a portion of a published article or internet post catches my eye sometimes because it needs further explanation A recent article referring primarily to positive displacement flowmeters stated under the leakage heading that fluid leaking past the moving parts rather than turning them can occur when a meter starts from a zero flow condition To avoid slippage at low flow rates installers may have to increase flow rate at startup then back it off once the right momentum is achieved Notwithstanding that leakage and slippage are different but appear to be used synonymously installers may have little interest in whether the flowmeter operates because they are typically long gone before operation begins In addition having to increase the flow rate every time flow is started is an excellent reason to consider another flowmeter or flowmeter technology Some years ago I noticed that a particular flow control valve was manually opened for about 30 seconds every day to remove accumulated solids This was not acceptable because we wanted the operators to focus on the operation not on minutiae and busy work Within a few weeks a different style valve was installed that did not plug In this case installation of a flowmeter that requires more than normal attention is not advised unless it is the only flowmeter that will work in the application In addition operators do not necessarily have the luxury of increasing the flow during startup because the additional amount of the material may create a hazard in some operations and or waste a valuable raw material or product In some plants no suitable location may exist to store the additional material It is bad enough to inherit a problem installation such as the above flow control valve but efforts should be made to not install new inconveniences that you or your successors will need to address FC David W Spitzer is a regular contributor to Flow Control and a principal in Spitzer and Boyes LLC which offers engineering seminars strategic marketing consulting distribution consulting and expert witness services for manufacturing and automation companies Spitzer and Boyes is also the publisher of the Industrial Automation INSIDER He has more than 40 years of experience and has written more than 10 books and 400 articles about flow measurement instrumentation and process control Spitzer may be reached at 845 623 1830 or via spitzerandboyes com Click on the Products tab to find his Consumer Guides to various flow and level measurement technologies Having to increase the fl ow rate every time fl ow is started is an excellent reason to consider another fl owmeter or fl owmeter technology 10 February 2019 Flow Control