Flow Control, Flow Control December 2017

Application Corner Audit flowmeters to be sure you get what you pay for S ometimes it makes sense to make sure you get what you pay for especially when large quantities of material and or energy change hands The problem is that by the time flowmeters aka the cash register are rigorously audited the various parties are often locked in a legal battle that makes resolving the technical problems much more difficult Let me give you a couple instances of how companies got into this position with the understanding that I cannot divulge information about specific legal cases A new sewage district contracted to have an existing water treatment plant accept its sewage Residents in the new district noticed their sewage bills were much larger than other residents already served by the water treatment plant The problem was traced to expensive surcharges for high flows during wet weather events Flowmeter performance was not seriously considered during the initial legal battle and the district was ordered to pay the invoices with the surcharges By the time I became involved residents in the new district did not even shop in the town where the sewage treatment plant was located My audit revealed significant flow measurement and calibration issues that were painfully resolved over time at considerable ongoing expense These issues likely would have been resolved quickly and more economically had I been involved prior to or during the original legal proceeding In another case two companies were locked in a multimillion dollar legal battle when as part of its strategy one company claimed the steam flowmeters used for billing purposes were not accurate The primary reasons for this claim were that the flowmeters were approximately 50 years old and had not been calibrated for about seven years The case was settled shortly after I audited the steam flowmeters and their measurements in conjunction with the steam generation process finding them to be surprisingly accurate despite their age and calibration history Repeating my opening statement sometimes it makes sense to make sure you are getting what you pay for FC A Coriolis mass B Differential pressure C Magnetic D Positive displacement E Vortex shedding T he question is vague in the sense that high viscosity can mean different things to different people in different industries All of these technologies are potentially applicable when dealing with a liquid viscosity of 20 centipoise cP which could be termed high in some industries Additional complicating factors Defining high viscosity as more than say 1000 cP reveals an entirely different set of considerations Positive displacement flowmeters that continually entrap liquid are often used in these applications because they exhibit low slippage unmeasured liquid at high viscosity However they are mechanical and tend to exhibit higher pressure drop with increasing viscosity Coriolis mass flowmeters can measure high viscosity liquids however performance can sometimes be compromised if the pressure drop across the flowmeter limits accurate flow measurement to the lower part of the flow range Magnetic flowmeters can also measure electrically conductive liquids that exhibit high viscosity As a practical matter magnetic flowmeters are not often applied to high viscosity liquids because the majority of such applications involve hydrocarbons that are not sufficiently conductive Differential pressure and vortex shedding flowmeters are generally not applied to high viscosity liquids because of their Reynolds number constraints FC By David W Spitzer Quiz Corner Which of the following flowmeters can be applied to high viscosity liquids 8 December 2017 Flow Control