Removing air from water pipe post chemical injection?

[turbzero]

Putting a simple water treatment plant together: We have a 25-40l/s system pumped through a 4" pipe. Water enters, is dosed/injected (via diaphram pumps) with Ph balancers, flocs, coags etc, mixed with in-line static mixer and then out. On the exit is an insertion mag-flow meter. We are worried about air in the water stream (possibly introduced during upstream dosing etc) affecting the operation of the mag-flow meter. Any ideas how we could remove this air pre mag-flow meter (we thinking simple run-through T with auto air release valve or similar)?

Another wrinkle to note:
The dosing and mixing happens in an upper (vert higher) pipe line, then the pipe returns 180deg and discharges through a lower line. Due to space it would be difficult to mount the air removal chamber/valve etc in the upper line unless it was immediately after the last injection/mixing point. We're thinking there should be a minimum straight run before attempting air removal?

Many thanks for any input..

 

[bimr]

One would doubt that you will have any problems with air in the proposed scenario. Most water treatment chemical reactions do not produce gas.

The magmeter will also continue to function with entrained air. The magmeter will show a larger flow reading than the actual flow reading.

Movement of the air through the pipeline is correlated to the fluid velocity. If the fluid flow direction is downward, the velocity would have to be approximately 3.5 to 4 ft/sec to push the air downward through the pipe.

If you want to trap the air, the best location would be where the pipe turns downward. Slightly oversize the dowward pipe at that location.

 

[turbzero]

Once again, many thanks bim.

I was thinking some air may have (potentially) come from the dosing procedure (such as if the chemical tanks ran down, loose pipe connections etc). The flow is fast and the magmeter is only being used for signalling purposes (i.e. the absolute reading is not vitally important). So at this stage I won't include an air removal fitting (I will however have the downward long radius bend fitted with flanges so we can retro fit something if we have to.

Thanks

P.S. If we did decide to fit an air trap, what type of auto air remove valve would you suggest?

 

[bimr]

Many prefer the ventomat valves.

http://www.ventomat.com/content_sub.asp?ssID=13

 

[kjmastaw]

Turbzero, we've (ENVIRON) have always used Val-Matic air release valves for large systems. For smaller systems, I'm not sure. Here's their website. You'll probably have to contact them to find your local rep.

http://www.valmatic.com/airrelease.html?gclid=COjwz52S86kCFYHs7QodH2_wYQ

Regards,
Kevin