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Member Posts: 168
I want to install steam main vents. Main #1 begins with 32' of 4" pipe and ends with 14' of 3" pipe (46' total). Main #2 has 32' of 3" pipe until it does a "T". The left branch has 14' of 2" pipe and the right has 14' of 2-1/2" pipe.

When the heating season is done, I also want to install top-of-riser vents.

How do I figure needed venting in each instance?

• Member Posts: 6,688
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Get Gerry Gill and Steve Pajek's e-book

"Balancing Steam Systems" available in the Online Store of this site. It has the capacities of almost every vent currently available as well as a bunch of older ones. Once you know the cubic feet of air in each main, you can choose vents that will pass that amount of air in a minute at 1 ounce pressure.

You'd do the risers the same way, but size the vents for 2 or 3 ounces so the steam would distribute thru the mains first.

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Aha!

Okay - Main vent(s) must pass main's c.f. of air in 1 min. at 1 oz. pressure; riser vent(s) must pass riser's c.f. of air in 1 min. at 2 or 3 oz. pressure. I got the mentioned .pdf file today and I see that you are named in the introduction or preamble.

By the way, where venting the risers is concerned, okay to vent them not at the very top of the riser but within a couple of feet of the top? This is a logistical issue (getting at the pipe).
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• Member Posts: 168
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I'm stuck on the math

Using the formula 3.14 x radius squared x length for each pipe diameter (3.14 being Pi), I calculated volume of 500 cu. ft. for steam main # 1, 270 for #2 and 294 for #3. A Gorton # 2 will pass air at 1.1 CFM at at 1 oz. pressure (my max. operating pressure). I obviously can't put 500 Gorton #2's on this main. I don't understand this - what am I missing?

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cubic ft vs cubic inch

I am guessing you have pipe volume in cubic inches and so if you take the Gordon #2 at a cubic foot that equals 144 cubic inches. Now that should help in sizing. Good luck, Tim
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Cubic Schmubic

A board foot has 144 cubic inches. A cubic foot has 1728 cubic inches. Easy to mess that one up!
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True, but Tim...

still made me cringe. I'm a dope. Okay, now where's that calculator again?
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i can't believe I messed that one up.

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here are my sizing results

• Member Posts: 168
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here are my sizing results

On a 2-pipe pumped system, would it be bad to use a Gorton # 1 (.33 CFM) to purge a main that has only .07 Cu. Ft. of air in it?

Alternatively, my risers have from .01 to .05 Cu. Ft. of air in them. With those low figures, would venting the risers really add much in the way of performance or energy savings?
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