gas flow switch

[tumbleweed]

Is there some sort of switch that connects in-line on a gas flow that when the flow reaches a lower flow leval that it sends a signal to a valve on a diffrent line that will swicth that flow either off or redirect it.
Tumbleweed

 

[way]

Yep, you can rig that up in a number of ways. Essentially what you are looking for is a flow switch setup. There are a lot of ways to do this, here are two: You can use an actual flow switch (kind of pricey), or you can use a pressure switch with an orifice or other restriction. You set your pressure switch or flow switch so that it will close a set of contacts when the flow or pressure gets too low. When the contacts close they trigger the event that cures the problem, i.e. close a valve, start a pump, or whatever. You will probably need to have some relays, solenoids, or motor starters in the mix.

There are ton of flow and pressure switches out there. Do a search on the web, or if you have a buyers guide start there. I'm sure that there are even a few in Graingers. Good luck.

 

[DaveBridger]

I've found one of the best solutions for gas flow alarming is to use a thermal mass flow switch. This type of measurement basically works on the delta T principle between the reference and measurement RTD detectors. Some advantages, it's simple to install on-line and has no moving parts. Couple of things you need to check first:
1)requires fairly constant gas specific heat ratio(cp/cv) i.e wide variations in hydrogen concentration will cause the calibrated range to shift.
2)gas is fairly clean.
To hook-up the flow switch to your valve (on/off valve, solenoid operated) should be a simple exercise.
Typical vendor would be FCI, but there several other vendors.
Good luck..!