Max venting needed for 3/4 inch main antler

Motorapido

I'd like to vent my main at the same capacity that it would vent if no vent were attached to the fitting and the pipe were wide open. I have two Barnes and Jones Big Mouths on an antler that joins the main with a 3/4 inch nipple. My single-pipe, parallel flow steam system typically operates between about 6 and 11 ounces of pressure, measure on a brand-new 0 to 3 psi gauge. Do I need to add any venting to move the maximum amount of air through that 3/4 fitting, or are the two Big Mouths currently allowing all the air to vent at the same capacity that air would vent if that 3/4 fitting were wide open?

Fred

A 3/4" pipe will vent at 9.5 CFM @3 ounces of pressure. The Bigmouths vent at 3.6CFM @ 3 ounces. Technically you could add another Bigmouth and get about 66% of its capacity but the amount of time you save by doing that simply doesn't justify spending the money. If you took off a good Gorton #2 vent to put the Bigmouths on, you certainly can put one of those back on the antler with the two Bigmouths to get the full venting capacity of te 3/4" pipe. The Gorton vents at 2.2 CFM at 3 ounces of pressure.

Motorapido

Thanks, Fred. The vent I removed and replaced with the Big Mouths was ancient and stuck shut, so I figure I'll bite the bullet and buy another Big Mouth, which will give me more venting capacity than the 3/4 inch pipe will pass. They sure are pretty to look at, and when I'm done, I'll know I've gone the extra mile. Thanks for the info.

Fred

@Motorapido , LOL, I like looking at mine too!