Air Release Valves 2

[tacogrande]

We have a long force main that has several high points in it. We have specified that automatic air release valves be installed at these points. However, the question has been raised about minor high points where the force main is deflected to route under storm drains.

Has this been encountered? and have maintenance or operations had problems where additional ARV's are not installed?

 

[BigInch]

That should not be of great consequence. Remember that any significant amount of air trapped there should simply increase the local velocity under the bubble until it is swept away to a higher point. Where static air traps are encountered is where enough air can collect at points high eough such that they are no longer swept downstream by local velocities hugging the air bubble and a column of air locks in a high point where flow is eventually blocked entirely by air reaching "air lock" pressure, a pressure that balances the combined air-water column weight against total remaining downstream pressure and thus remain in place. Those are the pipe segments that need to have air release valves.