Question on Air Valves for Small Diameter Pipeline

[Dersnerman]

Hello All!

I could use some feedback on the following application. I'm wondering what I need in terms of air valves for this 1km long, small diameter, low pressure pipeline. Drawing attached.

1) 2" diameter, 1km long pipeline. 2 high points where air can collect. Q = 10 GPM.
2) Same as above except 4" diameter, Q = 50 GPM.

Working pressures won't be more than 50 psi.

These are obviously very small diameter pipelines. I'm wondering:

a) What would you recommend for air valves? Standard practice and literature would dictate I need a combination air valve at every high point. However, in practice I've seen many similar small pipeline applications where no air valves exist at all. Most of the air will be evacuated through the end of the pipeline on system startup, but there could be some pockets left at high points.
b) should I be concerned with entrained air buildup at highpoints? How long does it typically take for entrained air to gather at high points? This pipeline is in operation for about 4 months and drained yearly.

 

[Dersnerman]

Thanks Pierre, that is a good resource and actually what I started with. I find Valmatic understandably perhaps overstates the requirement for air valves (understandably because they are in the business of selling them). But it's a good resource nonetheless.

-Andrew

 

[LittleInch]

Your fill pipe question, yes those are your two main options. You can also use small tappings at high points as a vent and then insert a screwed plug and maybe seal weld it.

Then coat it well before burial.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pierreick]

Hi,
Another document.
Pierre

 

[NW_Wash_Eng]

This seems similar to a topic I posted a week or so ago, as previously mentioned. The Walski number (P) is a useful tool however I have noticed it is flawed for the case of a vertical change in pipe elevations. Rise/run*100 always =0 in these instances. Unfortunately for me, I rarely use anything OTHER than 90deg changes in elevation. The data and posts from 1503-44 and LittleInch were awesome for me to understand and rationalize the reasoning behind most open systems rarely using ARVs. They are definitely worth the read.
And for what it's worth, I agree with your comment on Valmatic.