how many Gorton #2 to vent 24 cubic feet of main?

rhodebump

I am trying it calculate how many Gorton #2 vents that I should have for my system.

1st Main is 5" OD, 128' long
2nd Main is 4" OD, 60' long

According to the vent capacity chart (https://heatinghelp.com/assets/documents/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-1.pdf), this makes 24 cubic feet

It's the next part that I do not understand. There are 3 numbers for each vent type (1 oz CFM, 2 oz CMF, and 3 oz CFM). I don't know which number to use. Supposing that I go with the 1 oz CFM number, which is 1.100 for the Gorton #2, How many vents would you recommend?

Thank you!
Phillip

Hap_Hazzard

How are you calculating the volume? What pipe sizes are you assuming? I don't know of a standard schedule 40 steel pipe with an OD of 5 inches. Theoretically a 4½" NPT pipe would have a 5" OD, but I don't think that size is even available. How are you measuring the OD?

rhodebump

I measured the pipe by wrapping a tape measure around it to get the circumference of the pipe. Then, I used an online calculator to convert from circumference to diameter.

KC_Jones

See the below link for pipe sizing. Your method should be good, but the sizes need to line up with standard pipe sizes. It's not a simple matter of using the OD, measure OD and compare to the pipe OD on the chart. Also nominal pipe size loosely relates to the ID, not the OD.

http://www.pennusa.com/products/schedule_40.php

Hap_Hazzard

Actually, while the nominal pipe size derives roughly from the internal diameter, it's the outside diameter that is actually standardized across the NPS, while the ID is set for different schedule numbers. This is to allow standard fittings to fit all pipes of a given NPS regardless of the wall thickness. Hence, shedule 40 and schedule 80 pipes of a given NPS can be threaded with the same dies and connected to the same fittings.

Gsmith

Just using your approximate diameters and lengths I get 17.6 cf for the 128’ main and 5.2 cf for the 60’ main. You want the steam to get to the ends at about the same time. I’d use the 2 os/si number of 1.75 cfm for the Gordon #2; and I’d start with 3 Gordon #2’s on the long main and one #2 one the short main to get steam to the ends in about 3 minutes, you can always double that, but it costs more. Unless there is some reason you want or need the floats that are in the Gordon’s You could use Barnes and Jones Big Mouth vents which have about double the venting capacity for about the same price. But keep the same ratio, 3 vents on the big long main for each one similar vent on the short main.

JUGHNE

Is this single pipe steam?

JStar

I made this chart based on venting in under 10 minutes from the time the header gets steam.

Edit: Realized that it doesn't cover your pipe sizes. I'll update at some point.

dopey27177

When sizing main vents one must take into consideration the capacity of all the radiator vents. They also vent air fro the system. Remember this a boiler from start usually will take 10 to fifteen minutes to produce steam. Additionally, the piping has a fixed velocity for the flow of steam. Using excessive main vent valves or super capacity vent valves cannot vent more air than the velocity of the pipe will allow.

I have seen many configurations of venting on this site, I believe one Gorton # 1 is adequate for a main vent. The # 1 vents 4 cubic feet of air per minute at 1 PSIG. If one is not sure that this is not enough a T can be left out for additional vent valves.

Remember all the radiator vent valves also remove air from the piping system.

Jake

nicholas bonham-carter

Yes but you want the air in the main pipes exhausted first, so that the radiators all fill together.
The total mains venting should be more capacious than the aggregate of the slower radiator venting for this to happen.
A low pressure gauge will show the back pressure of venting in ounces when just firing up.—NBC

EBEBRATT-Ed

I am getting 14 cubic feet for the 5" and 4 cubic fee t for the 4"

KC_Jones

> @dopey27177 said:

> The # 1 vents 4 cubic feet of air per minute at 1 PSIG.

Just curious why you would recommend building pressure instead of heating the building?

In order to build 1 PSI you have to slow down the steam to do so, this would require inadequate main venting to accomplish the task, by definition. Pressure in a steam heating system is back pressure against the flow of steam, not something the boiler is creating.

gfrbrookline

@KC_Jones agreed the mains need to have adequate venting to vent them quickly, but where I think @dopey27177 was going is that the radiators need to be vented in a way that they can be vented slowly but still allow them to vent all of the air out of the run outs in a timely manner so the boiler doesn't build pressure too quickly after the main vents close.

JStar

Venting is a simple idea in a complex reality. We want steam to be made quickly at the boiler, leave slowly from the boiler, travel fast through the mains, and distribute slowly again throughout the radiators. Think about all those dynamics occuring at once!

When we balance a system with main and radiator vents what we're really doing is turning an open system into a closed system as soon as possible (when the main vents close). Then, we match the radiator vents' capacity to the back pressure (caused by air volume) and friction loss of the run-outs as closely as possible so that the boiler can build slightly more pressure than the run-out is losing, causing positive forward motion, and hopefully filling the radiators with enough steam to match the heat loss of the room.

In well balanced systems, the boiler pressure should barely rise above the total static pressure of the longest run in the system. In fact, that's how we detetmine our pressure setpoint. But the required pressure for the longest run is more than what's needed for the shortest run. In larger systems I would give the longest run first consideration, then choose all of my radiator venting from that baseline.

dopey27177

Gorton #2 vents is over kill. The Gorton # 1 vents $.08 cubic feet of air per minute.

Since a boiler from a cold start takes 10 to fifteen minutes to produce steam at pressure you do not need anything larger than a Gorton # 1 on each steam main.

Save your money and use the smaller valve.

Jake

ChrisJ

dopey27177 said:

Gorton #2 vents is over kill. The Gorton # 1 vents $.08 cubic feet of air per minute.

Since a boiler from a cold start takes 10 to fifteen minutes to produce steam at pressure you do not need anything larger than a Gorton # 1 on each steam main.

Save your money and use the smaller valve.

Jake

My boiler from a cold start takes 20 minutes to produce steam.

However, on a very cold night it only takes a 60 seconds to come to a boil and to get steam to the ends of the mains and I vent them at 0.009 PSI under those conditions. This requires five Gorton 1's on a 29' long 2" main and a single Gorton 1 on a 11' 2" main in my situation. Even 4 G1's isn't enough on a short 29' long 2" main.

I do not understand your reasoning Jake?

What does the time it takes to bring a cold boiler to boiling have to do with how fast we want to vent?

Hap_Hazzard

@ChrisJ, if I'm understanding correctly, he's not suggesting venting any slower; he's saying saying that, after a certain point, a bigger vent won't vent air any faster if the existing vent is already keeping up with the rate at which the boiler is producing steam.

I have to agree, in principle. I just don't know enough about the physics involved to be sure about where that point is reached, but he seems to know his stuff.

ChrisJ

Hap_Hazzard said:

@ChrisJ, if I'm understanding correctly, he's not suggesting venting any slower; he's saying saying that, after a certain point, a bigger vent won't vent air any faster if the existing vent is already keeping up with the rate at which the boiler is producing steam.

I have to agree, in principle. I just don't know enough about the physics involved to be sure about where that point is reached, but he seems to know his stuff.

That is correct, however it most certainly is not a single Gorton 1 per main. Especially on a system with a 5" main.

dopey27177

Firstly as the boiler begins to make steam, the steam pushes the air out of the system. When steam reaches the vent valves the close and allow the system to pressurize. While the main vent valves are closed the radiator vents vent air till the steam reaches the radiators.

As steam becomes condensate then volume shrinks and causes a slight vacuum. At that juncture the radiator vents allow air into the radiator to break the slight vacuum allow the condensate to drain. While all this is happening the main vents remain closed.

When the boiler shuts down all the steam in the piping condenses and a vacuum is formed, at that time the main vent
valves open and break the vacuum. (Steam volume is 1700 times the volume of water because of change of state a vacuum will form.)

Again look at the cubic feet of air in your pipe. ( Imade a type O for the # 1 vent.) It vents 4.08 cubic feet of air a minute, more than enough to vent the air out of your long steam main.

Your large main I believe is 4" pipe which has about 11.52 cubic feet of air when the boiler is off line, that translates to 3 minutes to vent the air out the piping.

Your smaller main I believe is 3" pipe which has 3.18 cubic feet of air when the boiler is off line. This translates to the air being removed in less than one minute, also the radiator vents are releasing air from the system.

Why use such a monster vent valve Gorton # 2 when you know the valve closes when steam reaches it and stands there as does nothing for the boilers duty cycle.

The Gorton # 2 vents 16 cubic feet of air times two ( 32 cubic feet of air ) and you only need to vent about 14 cubic feet of air from both steam mains.

You made my case a hot boiler takes 60 seconds to steam, all the pipe and boiler is hot so the air in the system is at near steam temperature and that will cause the vent valve to close relatively quickly. Therefore the the main vents will close very fast,

Jake

ChrisJ

@dopey27177

A Gorton 1 only vents 0.33 cubic feet per minute at 1 ounce.

1 Ounce which in my opinion is still too much back pressure during main venting.

dopey27177

Why do worry about back pressure or one ounce of steam when the system m operates at plus 1 PSIG

Jake

JStar

> @dopey27177 said:
> Why do worry about back pressure or one ounce of steam when the system m operates at plus 1 PSIG
>
> Jake

Because every system starts at zero, and that's when we need to vent the air.

Hap_Hazzard

ChrisJ

dopey27177 said:

Why do worry about back pressure or one ounce of steam when the system m operates at plus 1 PSIG

Jake

Here's my single pipe system heating on a mild day. All 10 radiators had steam to them and were heating the spaces. This is the same pressure I see while the main vents are active.

https://youtu.be/zyxLbXq61-U

KC_Jones

dopey27177 said:

Why do worry about back pressure or one ounce of steam when the system m operates at plus 1 PSIG

Jake

It only operates at that pressure if you force it to with an over sized boiler, or inadequate venting.

As @JStar said the starting point for main venting is zero, it only climbs from there when you don't have enough venting.

ChrisJ

KC_Jones said:

dopey27177 said:

Why do worry about back pressure or one ounce of steam when the system m operates at plus 1 PSIG

Jake

It only operates at that pressure if you force it to with an over sized boiler, or inadequate venting.

As @JStar said the starting point for main venting is zero, it only climbs from there when you don't have enough venting.

@JStar know's his stuff.

LS123

@ChrisJ and all.... I also have 70 year old boiler with efficient oil burner on it. I recently put 2 gorton #2 on my mains supply line. one on the main pipe closer to the boiler about 10 feet, the other one going to the front of the house L shape, about 25 feet... the two new gortons # 2 has made a huge difference ( I used to have very small main vents, one was probably broken steam was coming out of it and I would loose gallon or two every 24 hours (with the old broken main vent" I think it was vent rite 75 or 25 something like that. I also replace the pig tail pressure gauge with low pressure gauge... my steam boiler start producing steam in about 25 to 30 mins and works on about 1/4 th of pound of pressure...