Sizing/Spacing combination air valves...

[Mikelt98]

I am designing a 20" water main. Client specifications require CAV's (they used Valmatic 200 C.2's on a recent 16" project) at high points, but offer no guidance on sizing/spacing. Can anyone point me to a reference? Thanks in advance!

Mike

 

[gerhardl]

I have myself found no references, not meaning that there is none. If you find any. please post to this thread, I would be highly interested.

However following to your question:

a) Someone has to be responsibel and acknowledge the design criteria. Normally this would be the owner, builder or end user.. the juridical person that ultimately will end up with the responsibillity of possibel malfunction of the total installation.

b) Criteria for design to be selected on basis also of total concequences, Bursting or collapsing of a line will have larger consquences in a city than in a desert. More safety devices if critical.

c) Air out. Corresponding to max planned or actual filling rate.

d) The difficult one is air in by pipe bursting conditions.
This would correspond to max water out. This again to physical properties of the pipeline, layout, buried or open etc, and the presence and placement of bursting valves (valves closing by bursting pipe). The value has to be calculated/estimated.

f) On basis of above, suppliers will offer air valves with suitable capacities. To compare offers : ask for actual areas of the valves and at what air speed the air inlet and air otlet is calculated. Some suppliers tend to give high speeds, leaving little reserve capacity. Calculating speeds for estimates: 80-120meter/s.

g) Distance between? Normal would be all high points where air could give problems. At long flat streches..???

 

[rconner]

I think if you do an "advanced search" on this site you will find that there have been some published works, a whole lot of (sometimes it appears much varying) opinions, and perhaps some research by some folks mentioned on this subject (e.g. see the thread

http://www.eng-tips.com/viewthread.cfm?qid=147327

and multiple links to other threads by different responders pasted therein -- don't worry about the subject of that particular thread, though there are obviously some special conditions involving air valves in sewer and other product forcemains.) I think the opinions vary from use at all high points and even more frequently/regularly spaced (regardless of grade) favored by some, to some bringing up they aren't used much or at all on petroleum pipelines! I think an overwhelming consensus would agree some sort of air valves are definitely helpful or essential at high points in bleeding the air out at least for a proper hydrostatic test as required by most procedures and standards, if not with regard to accumulations and other effects in some operational/flow conditions! I think most would also probably agree that air has caused at least some problems in pipelines.

 

[Mikelt98]

Thanks for the info. I've requested a copy of AWWA M51 from our library for reference. Will look elsewhere too! This forum is an excellent source of info - I wish I had found it ywears ago!

Mike in St. Louis

 

[sbush]

Here is a link to the Val-Matic Web site for valve sizing:

http://www.valmatic.com/pdfs/arv_size.pdf

S. Bush

http://www.water-eg.com