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Greg: Our April puzzler on why a vortex meter measuring toothpaste went bonkers wasn’t so puzzling for our more experienced engineers, Ronald Bruton and Hunter Vegas.
Ronald: The viscosity of toothpaste is probably too high to get a nice, fully developed turbulent flow, without which you don't get predictable vortices. Even if the Reynolds number indicates fully turbulent flow, it is probably based on a constant viscosity, which would not exist with toothpaste anyway. At best, toothpaste is a Bingham plastic; at worst, some bizarre thixotrope.
Hunter: Now this one was too easy. You need to be well into the turbulent flow regime to generate consistent vortices for the meter to work. With toothpaste's viscosity, it's going to take quite a flow rate to get there! Some interesting things that have created vortex meter headaches:
Stan: We had a mess of problems--particularly for about the first 10 years after they were introduced. I remember when the president of engineering showed up in my office wanting to know why the meters didn’t work on the big new project. When I later told my boss that the big guy came to me and not vice versa, he still said, “I don’t know why you talk to him. Every time you do, I get in trouble.” I was good at stirring things up. It may be the reason an agitator from a washing machine turned up my office one day for the “agitator of the month” award.
Greg: There were significant improvements in the technology over the next couple of decades but, as per Stevie Ray Vaughan, there were the sources of great blues from the double trouble of an erratic vortex separation and velocity profile by pushing the limit. Sometimes we forgot that a vortex meter has requirements for straight runs upstream that get more stringent at low velocities.
Stan: The rangeability of a vortex meter is based on a meter size that often corresponds to pipe size that is smaller than what is economical in terms of a system pressure drop.
Greg: I am sure there are a lot of great stories, which we didn’t get before the editor in chief’s deadline. It now takes us up to four months to get a reply into Control Talk, so hang in there. The following is an excerpt from an interesting reply to the March puzzler from Dietrich Schilberg.
Dietrich: Just because the temperature starts ramping does not mean the process is integrating. It may in fact be ultimately self-regulating, but with a long time constant (lag). It turns out this doesn't matter much, because you tune a loop the way it first starts to respond.
Stan: Here is also a recent reply from Calvin Burnett to our January puzzler on the shift at high noon.
Calvin: If it's not too late, I had the exact same issue with a mass meter. A contractor decided that the mass meter was a comfortable spot for him to eat his lunch. The tubes don't vibrate at the same frequency with a 200-lb. pipe fitter perched on top.
Greg: Now for a Top 10 List from Jonathan Mertz (son of Glenn Mertz) that every parent can relate to these days:
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