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Our company is installing flow meters on an old polyurethane foam machine. After some research, ultrasonic flow meters were chosen as they have no moving parts and are easy to clean. Polyurethane foam is produced by mixing polyol with isocyante (not as bad as it sounds) at a fairly precise ratio. However, the ultrasonic flow meter will not work with the polyol. The polyol we are using is the polyether type.

According to the manufacturer any polyol should not be a problem, nor should the viscosity be a problem. Apparently they have used the same flow meters for honey and glycerin and they work well in those applications.

Why would the flow of polyether polyols not be able to be measured in an ultrasonic flow meter?

oorst
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  • What are the working limits for diameter, detect length, flow velocity, pipe material , pipe thickness etc. I used one of these and had accuracy issues - when i contacted tech hrlp he was surprised i was even getting a reading... – Solar Mike Jul 11 '17 at 03:40
  • It's an inline meter. The measuring transducers are part of the actual meter. The nominal diameter of the meter is 20 mm. At this stage we haven't had material flowing through it. Commissioning involves filling the meter with fluid to calibrate, but the meter thinks its empty even though its filled with polyol. – oorst Jul 11 '17 at 06:04
  • My first suggestion is to fill the meter with a selection of fluids to see if it detects them - and to within spec to check if the meter is functioning correctly. Then you can pick on the polyol... – Solar Mike Jul 11 '17 at 06:29
  • Forgot to mention it works fine with water. Also part of the commissioning. – oorst Jul 11 '17 at 06:36
  • So add all useful info - commissioning results etc. Then what about using fluids with similar properties to polyol , density, viscosity etc and narrow down where the meter fails – Solar Mike Jul 11 '17 at 06:39
  • Yeah I'm going to grab some glycerin from the chemist on the way home. We'll see how that goes. – oorst Jul 11 '17 at 06:45
  • @SolarMike Solved. The speed of sound in our particular type of polyol is about 1900 ms-1. The meter requires that the fluids have a max speed of sound of 1800 ms-1. So close. – oorst Jul 11 '17 at 23:11
  • Ahh, that's a shame, so you're stuck with that polyol - have you looked at other flow meters - the one I used had two separate sensors that clamped to the pipe, which needed to have fully developed flow in the pipe to provide an accurate measurement - mind you the Engineering Dept at the Uni bought it (can't remember the cost but not cheap...) : I got to play with it !! Best of luck. – Solar Mike Jul 12 '17 at 16:37

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