Using a Larger Combination Air Valve on a Smaller Pump Mains

[ntandomansa]

Hi Guys

I hope this message finds you well. I am currently evaluating a scenario in our project where we are considering the use of a 4-inch (100mm) combination air valve in a system that has a 2-inch (50mm) pump mains line. Before proceeding, I wanted to gather your insights on the potential implications and feasibility of this approach, especially through the use of reducers on the flange connection of the valve onto the Tee on the pipeline.

Are there likely going to be any challenges or considerations we need to make?

 

[LittleInch]

Needs a drawing.

What's a combination air valve? Vacuum and air bleed together?

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

 

[swazimatt]

higher cost implication for larger AV as well as having additional reducers to bring the 50mm up to a 100x100 Tee (I doubt there is a 50x100mm tee, and using a 50x50 Tee with a reducer up to the AV takes away the benefit of using a larger AV) You would also need to make sure the larger AV operates as it should under your pressure conditions
the cost would also go up with larger manholes and possibly deeper pipelines depending on your configuration.

Normal AV installation is to have the upstand part of the tee 1/3 to 1/2 diameter of the pipeline to catch bubbles, if you went with a 50mm tee and AV you would be fine. What is your motivation for using the larger AV? Contractor (or farmer) has one sitting in his shed?

 

[bimr]

It would be easy enough to use a 2 x 4 bushing to install the larger ARV.

Having said that, you have not provided a reason for it. Is this clean water or sewage? Can you use a manual valve for startup of the pipe network instead of an ARV?

 

[NW_Wash_Eng]

I believe Combo valves are sized based on the flow in the system, not so much the sizing of the pipes. You need to be able to outpace the air that you are pushing through (air release) and allow in more than you are removing (vacuum break. In my experience the combo valves are capable of much more volume than you'd expect. Check this document out, it is very helpful. While it is branded the basic concepts work with a majority of the big name suppliers.

https://www.valmatic.com/Portals/0/pdfs/AV_TheoryApplicationSizingAirValves_4-18.pdf