Does anyone have any experience with flow measurement of a dusty/wet air mixture flowing in a 24" cooling duct. It doesn't need to be an
accurate flow measurement - just whether the supply fan has failed or is there a major flow restriction in the cooling duct. The site is an aluminum smelter that has a series of air fans blowing air through 24" ducts to cool the power buss. The accessable duct (~6 ft) is inadequate to protect a common pitot tube from the fan air turbulance. Rain/moisture/dust is often sucked in to the air duct and coates the surface of the pitot tube.

Thank you for your ideas.

 

How about a downstream dp transmitter. Too low of a dp indicates no flow, too high indicates plugged.

Bob Peterson

 

Hot film sensors would work very well for this.

drop me a note off line, I can help you with a design or a suitable device.

Technical Consultants
[email protected]

 

An industrial grade limit switch with a paddle attached to the arm should be reliable. The size of the paddle would set the threshold.

Regards

cww

 

See the flow switch at: http://www.almegcontrols.com/flow_switch_stainless_steel.htm

It has a 1" NPT with a paddle. You can request a custom paddle length. SPDT switch either off or on.

Bob Hogg

 

One approach is to measure the DP across an available elbow or pipe restriction. Contact me if you would like more details.

John Catch
http://www.inflowinc.com

 

I would you a current sensing switch on the fan. something like an H908 from Veris Industries.

 

Any kind of differential pressure airflow switch would work. Just put the sensing tube on the top side of the duct to keep the water out.

Some are available for about $70 at http://www.mcmastercarr.com

I have used them with great success on cooling applications.

David

 

Look into an AIR FLOW SWITCH from Fluid Components International (FCI). Great turndown, and works on extremely low flow.

Contact me at [email protected] if you need more info.

 

I agree with Bob and Curt.

I foyu are looking for simply flow/no flow use a switch with a paddle. Can't beat the simplicity.

If contact bounce is a problem use a debounce circuit/logic on the input and a snap action switch.

-Rob A.