Compensating flow regulator

[dhfire]

I am looking for a way to vary the % of fire fighting foam to water solution without electronic flow meters. I would like to have a constant 3 gpm flow of foam being pumped thru a regulator at 400 psi and returned to the foam tank. By mounting the regulator to a panel and manually adjusting it to get b/n .1 and 1%, I need an additional compensating element from a (mechanical)device on the outlet of the pump to tell the regulator what the varying amount of the water flow is. So essentially by setting the manual adjuster to say 1%, this compensator will bypass foam into the water solution at 1% whether the pump is flowing 50 or 300gpm.
Thanks for your help.

 

[zdas04]

Have you looked at eductors for this? The application seems very similar to a hose-end sprayer (the most common form of eductor) and would give you the control that you are looking for without a lot of touchy electronics.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.