Can an Air Release Vent be relocated?

[WSUgrad]

I have read a little bit in this forum on the science behind Air Release Vents. I gather they are usually @ high points in water distribution lines and usually are only found on large trunk lines. I have a project with a 54" watermain. We have a proposed road going through the existing location of an air release vent.

2 Questions:

1. If we relocate this vent 100' down the line (I don't know the gradient from it's existing location to the proposed one, I assume it's not that drastic) will this affect the watermain adversely or what are the possible effects I should expect?

2. Would anyone happen to have a spec for construction that I may have a look at and modify for my own purpose.

Thanks.

~Chris

 

[CivEnvEng98]

It really depends...

If the apparant high spot is a really big one, like 100' long and you can move the ARV to that side of it, no problem. You need to get a hold of the as-builts/record drawings on the line and see what you're up against.

Moving the ARV away from the high spot can minimize it's effect on purging air from such a large dia main. Do you want the liability if they start having problems with air in that line? Heck keep it where it is.

If the ARV is an automatic and in a manhole...why can't you keep it where it is and build your road on top of it? For example, just adjust the frame & Cover of the existing manhole to match finished grade, using brick & mortar or concrete rings. ARV manholes usually aren't lined with hdpe or fiberglass or whatever so it's not that big of a deal even if you had to add a barrel section to the manhole for big grade changes.

Best of Luck!

 

[RWF7437]

First, contact the Owner of the water line and ask them how they want you to handle the problem. They can provide most of the information you need and, in the end, they can veto any idea you might come up with. Also, they'll appreciate the courtesy if being asked first.

good luck

 

[stanier]

It depends if the air valve is there for maintenance, ie scouring or line filling or as a waterhammer mitigation measure. If for the latter then the surge analysis may need to be revisited.

For information ionn the latest technology for air valves i suggest you visit

http://www.ventomat.com.

Changing the location of the air valve mayu allow you to implement sdome of the recommendations made by Ventomat.

There are a widfe variety of air valves in the market place. many are copies of valves where the patent has run out. the companies making them have little idea of the basic design and operation. they in fact sell metal "shapes".

the style of valve from ventomat or Fox/CSA will give you a more robust type of valve. As the main orifice is the size of the valve you may be able to design for smaller valves. Many legacy air valves have much reduced orifices.

For more reading you wish to look at the work by HR Wallingford on air in pipelines.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[rcooper]

Could you vent the air to a more convenient location through say an 80mm continuously rising pipe and fit the air valve on the end of the vent? It's not something I have done, but it is something I have thought of doing.

There may be a problem with having the long dead leg if the water is potable.

 

[WSUgrad]

Thanks for all the ideas/suggestions. I was unaware that these could be put into manholes. I don't have all of the asbuilts as of yet, I will check into those and weigh the options as well as contacting the WDA and finding out their recommendations or guidelines.


Through more investigation it appears that we are not going to move the physical location of the arv but rather re-routing the connecting pipe to somewhere outside the influence of the pavement. The things we have to be aware of are other utility conflicts as the pipe must be continuously rising to avoid the "kitchen sink" drain affect of trapping water in the re-routed pipe.
Again, thanks for the help.

 

[francesca]

I imagine that the service outage on a 54" water line during relocation of an ARV would not be tolerated given the safety (fire protection) implications and the extent of the area affected.

 

[stanier]

Two challenges with putting an air valve in a manhole if required for surge mitigation:

1) The manhole needs to be vented such that the ait can get in and out of the pipeline.

2) If it is vented the vent needs to be taken to the side of the road so that rain water does not fill the pit. If the manhole fills with effluent and there is a negative pressure wave you can contaminate the line.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[gerhardl]

Hi WSUgrad,

The short answer is yes, but as you can see from others answering, it is a number of constructional, practical and functional questions to be answered.

Let me try to point to a few, in my mind, essential questions to be asked:

a) Get the original calculations and functional demands for the air release. Check against present pipeline requirements, main being requirements for venting under pressure, filling of pipeline(air out) and pipe bursting (air in).

b) If originals not existing, or not found, or application or requirements altered or not required, or even when originals found: evaluate once more, and get signed / recognized that this is the technical basis for selecting the technical solution.

c) Construct new outlet/inlet in according to above. Other / nearest (if existing) and total solution for pipe taken into consideration.

It might be necessary to stretch a separate airing pipeline from existing (high) point if this involves any sort of built-up high-point. If the media is drinking water(or even anyway!) this should be avoided as complicating.

Better is blind off / shut off existing as far down to pipeline as possible, moving downstream, building up new highpoint (DN200 or DN150 probably sufficient under 'normal' conditions filling or emptying or release under pressure) and set in one or two triple acting air release/intake valves.

Note! Air intake for pipe bursting to be carefully checked, conditions may require more than given above. Air out capacity equals filling capacity of pipeline. Normal is 0,25m/s filling speed. Outflow by bursting: locally consideration!

Capacity of Airing valves to be checked!