Comparative Flow Sensors?

T

travish

Member
Location
Central North Carolina
Occupation
Electrician
Hey,
I have an application at work I need some help with. We have a 45 ton chiller (water) that is the cooling source for an injection molding plant. We have 11 injection machines that we run over night unattended. I would like to verify water flow both to and from each machine, to know that there isn't a water leak at the machines. So I need to know volume of flow, to and from, I need analog feedback. I would compare the feedback from "supply" line with "return" line at each machine with a plc, and turn off the water to the machine with an Asco Valve, if there was a substantial difference between the 2 I would know there was a water leak.

The logic and control is very simple, but not easy to pay for. I was shocked at how expensive flow sensors with feedback are. I would need 22 sensors to complete the project. is there an economical way to accomplish this? or does anyone know an easier way to do it?

thanks for any advice
Travis
 
How accurate do the flow sensors need to be?
IE what is the total flow during the molding process and what amount it that his a leak? Are there other ways to measure cooling such as inlet and oulet temp? Temp sensors are less expensive than flow.
Same with pressure.
What is the cost of product loss vs instrumentation?
 
I am not very experienced in fluids but wouldn't the heat rise through the injection machine, increase pressure, making flow readings differ between both points?

How drastic of a leak?

Could you get away with having only one flow meter down stream of the injection mold that alarmed after the pressure dropped below a certain point? As in at a 50% threshold the only probably reason would be a leak?
 
Coriolis mass flow meters would do the trick. They have about a 20:1 turndown ratio and come in low flow rates. I'd bet someone makes a differential version of them.
 
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