air-water ratio dtermination

[ratash]

I have an atmospheric water sump tank with a pump. I need to pump the water out to a river through several miles of pipe. I need to add an air/water separator in the line before it reaches the river, so that all the entrained air can come off before water enters the river. The pipeline goes up several hills and then goes down hill into the river.
How do I determine how much air to water ratio I have to size the separator?

By the way, the line will be pigged at the start up to get all the air out. The customer does not want air bubbles coming out on continous basis when the system is running. That is why we need an air/water separtor before water gets to the river.

 

[triniengineer]

After the Pigging Operation is completed, the line will be filled with either the process fluid, water, inert gas etc.
The piping configuration on the Launcher Skid if properly valved will prevent any entry of air.
I do not see how air re-enters the system unless your pump is cavitating - in which case those bubbles are the least of your problem.

 

[ratash]

Thanks.

 

[BigInch]

trini,

Water almost always has entrained air that is released in pipelines, hence air valves are used to release it at high points along a pipeline.

cavitation does not produce long lasting air bubbles. When the water reaches discharge pressure, those bubbles have collapsed due to the higher pressure.

ratash,

You might not need a separator. Have you considered air release valves?

I have not failed. I've just found 10,000 ways that won't work."-Edison “If Edison had a needle to find in a haystack, he would proceed at once to examine straw after straw until he found the object of his search. I was a sorry witness of such doings, knowing that a little theory and calculation would have saved 90% of his work.- Tesla

 

[ratash]

You are brilliant, because that makes sense. To me once the start up is over, there should be no air in the system. I am curious how the air gets in. Regards-

 

[triniengineer]

BigInch,
Thanks - I learnt something

 

[ratash]

BigInch,

Who is the manufacturer of these valves, and what kind of valve is it? Our route has several high points. Thanks-

 

[ratash]

BigInch,

Please disregard my last question, I found the information on those valves.

If you were to figure out how air can be entrained, how would you arrive at that number? My pressur eis about 100 psig.

 

[ratash]

BigInch,

Please disregard my last question too. Your mention of air release valves helped a lot. Regards- RATASH

 

[BigInch]

Look for the maximum soluability of air in water at given pressures and temperatures. If the pressure or temperature of the water changes from what is at the pipeline inlet, it will take in more air, if possible, or reject the air that it has, according to whatever the maximum amount is that it can hold at the pressure and temperature of the pipeline at any point. However, bubbles released at all points may tend to collect at the high points nearby. Which high point depends on the velocity and pipeline slope and if they can float upstream against the current or must move downstream with the pipeline velocity.

http://www.engineeringtoolbox.com/air-solubility-water-d_639.html

Ya. This website is a good place to learn stuff.

"I'm all in favor of keeping dangerous weapons out of the hands of fools. Let's start with typewriters."
- Frank Lloyd Wright (1868-1959)

 

[ratash]

Thanks. You are the best!