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.
 
What are the line sizes? Dp flow calcs can be done in the plc if needed... Good ole mag meter would be less expensive than Coriolis, vortex even cheaper than them all, but they all have considerations to be made.
 
thanks for all the replies, I couldn't get pressure or temperature to vary enough with small leaks to work. I think flow meter is the only option. I could possibly get by with only 1 meter in the return line at each machine to cut cost, and just look for a reduction in flow while running. this would require a set up person to correctly adjust the setpoint to match the flow rate for each mold every time we did a change over.

Does anyone have any experience with these sensors from Automation Direct?

FSC15-00-42-50H

thanks
 
if we keep the hoses in good shape, we don't have many leaks, however if a hose if rubbing or chaffing something, it would normally spray on the frame of the machine wherever it was rubbing and just run on the floor , if a hose ruptures, all bets are off. it could spray 10-15 feet away from the machine.
 
IMHO... What about just adding a pressure sensor down stream of the machine. Any sustained loss of pressure should imho indicate a leak.
 
the manifold that feeds/returns all 11 machines is a 4" line to and from the chiller. when I tried simulating a leak (disconnecting a line on one of the smaller presses) I didn't hardly see my pressure gauge needle bounce, I guess the system return pressure is stable enough that when I disconnected a line it just steady maintained 40psi. what ever loss of flow that I created by disconnecting a line the pressure in the manifold over rode the volume/pressure of the return line? I am not certain that is a good answer why I saw very little difference, but it is the only one I can think of.
 
travish said:
the manifold that feeds/returns all 11 machines is a 4" line to and from the chiller. when I tried simulating a leak (disconnecting a line on one of the smaller presses) I didn't hardly see my pressure gauge needle bounce, I guess the system return pressure is stable enough that when I disconnected a line it just steady maintained 40psi. what ever loss of flow that I created by disconnecting a line the pressure in the manifold over rode the volume/pressure of the return line? I am not certain that is a good answer why I saw very little difference, but it is the only one I can think of.
Click to expand...
What is the total flow for the 11 machines? What is the highest and lowest flow among the machines?
 
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