steam vent calculations...?

tom_82

Hi All,

I would like to see if my calculations are on target.

Thanks, I love this site!

My calculations seem to be pretty high. What do you all think?
This is a large one pipe system in a court yard building.
We have two main runs Left and Right. Left is one main with run offs (L).
Right is one main which splits into two (Rmain, Ra and Rb).
All three inch pipe.

L -160’ long ------- 17 gorton #2;

Rmain – 80 long---- 8 gorton #2;

Ra – 80’ long -------8 gorton #2;

Rb – 50 --------------5 gorton #2;



My calculations are based on 3oz of pressure and shooting for ten minutes (a stab in the dark)
I used, A = pi x radius squared x length in feet divided by 12 divided by2.2 divided by 10.

THANKS!
T

Brad White

There are better ways to send Mrs. Gorton

a marriage proposal....

This is what I get: 3" pipe has 0.05134 cubic feet per foot of pipe. (7.393 square inches transverse area x 12 inches long, divided by 1728 cubic inches per cubic foot.)

Your 160 foot main has 8.2144 CF.

A single Gorton #2 at 2.20 CFM (3 oz) would evacuate that main in 3.73 minutes, call it 3:45. Put on 17 pie plates like that and you will vent it in 13.2 seconds. Those 17 vents alone may get you to first base

Your 80 foot mains have 4.11 CF call it.
A single Gorton #2 will vent that portion in under two minutes. Eight of them will get you there in 14.0 seconds. The little guys win! (Swiss Timing).

Your 50 foot segment has 2.5675 CF. Just about 1:10 venting time with one Gorton #2 and with five you are down to 14.0 seconds like your 80 foot run.


I would cut back a bit on the venting to two on the 160' run and one each on the 80' runs. That will get you down to about two minutes each. For the 50 foot riser, two Gorton #1 vents will do about the same timing, just under two minutes.

That is my take. But I think I broke Mrs. Gorton's heart along the way...

tom_82

english wasn't my major soooooo

Thanks Brad,
THis is Tom from Brookline by the way.

So, first I calculated wrong (oops)...I think multiplied the diameter not the radius. Second, OOOHHHH, as I began to write this I understand, I think that after you end up with the total cubic inches you have to divide them by the amount of cubic inches in a foot....It seems like such a small amount of cubic feet for such a big pipe....Hmmm.
We are having new vents put on our system and I wanted to check the measurements make sure we are on the right track.

Last night our boiler was on for over an hour at start up! we have some new vent rite 77's down at the end of the run that splits, but they don't seem to be doing much.
facing 3.10 a gallon in heating oil, we want to get this beast under control.
thanks for replying. I am glad I checked my numbers before I said anything specific to our contractor...
T

Brad White

Hi Tom

Sorry, I had not gathered it was you...

You have a very good contractor (MG) working on your system I understand. I would not want to be put in a position to second-guess him and would have declined...

Go with what your contractor says- he gets high marks from others I have heard independently.

You are in good hands.

Brad

tom_82

Brad,
Thanks again.
I'm not trying to put anyone in an awkward spot, just trying to oversee things...We have had a hard time in the past and are a little paranoid about getting drug over the coals... Thanks for the positive reference.
T