STEAM PIPE MAIN VENTS RATINGS

ww

I notice that the popular vents are rated at 1 lb of steam. Since lower pressure than that is the ticket how do you calculate the amount of vents needed since generally there is no low pressure gauge on boiler and whether or not the pressuretrol is on the money with the gauge cut in and differential scales?...i'm making some estimates based on 1/2 lb but not really sure.

i have about 40 feet of 2 inch steam main and presently have a gorton 1 and 2 on long side and hoffman 75 and gorton one on the other and the steam is stalling in some radiators and doesn't get to the valve quickly. the mains heat up in no time though.

i also read an article about taking the vents off and timing how long the steam takes to get to the opening at the end of main..when do you start timing this event..do you need someone at the boiler to tell you when the outgoing piping starts to get hot..or release the pressure relief valve...what is the actual starting point?

I've seen so many vents on one main...sometimes more than six...and see that even though some are rated
at higher cfm output that they close quicker. just wondering if the approach i'm taking is correct.

DanHolohan

If you're talking about the rating that the manufacturer shows in there catalog, that's most likely the drop-away pressure of the vent, which is the pressure below which the system must go at the end of each cycle if the vent is to reopen and continue venting. They sometimes refer to it as operating pressure.

ww

this is what i meant..i read this here in one of forums...


A Gorton #2 will vent 1.75 CFM at 2oz pressure. A Hoffman #75 will vent .75 CFM at 2oz. If this is a smaller system, getting it vented out in 1 minute at 2oz should be sufficient, but keep in mind that you start at 0oz when venting out the mains. At 1oz, those CFM ratings drop to about 2/3 of the 2oz ratings.
http://forum.heatinghelp.com/discussion/144994/main-vent-question


ok..good to know..thanks....don't know if that's the same thing but it's useful info.

what i'm doing later is this...i'll loosen the unions holding the antlers on...wait for the steam to come out and wait a bit...then retighten...

if the steam comes to the radiator valves at all the radiators maybe this can prove if the vents aren't enough since i think there may be air in branch lines..just an idea.

Abracadabra

@ww I think what you are looking for is the book gerry gil and steve pajek put together that lists main vents, radiator vents and steam trap venting capacities.

Start your timing when there's steam in the header. IIRC,
rule of thumb is one gorton 2 for each 20 feet of 2"

http://store.heatinghelp.com/product-p/300.htm

100% of the price of this e-booklet goes to charity

ww

yes...good pickup...that's where i got that info regarding the timing taking the vents off..i remember reading that and referred to the article again tonite.i see that has alot of good info in it.

article also says that the vertical mains have to be vented too...there are pipes leading right into the radiators from the basement to the top floors...they are the same diameter as the branch pipes off mains so i guess these are not vertical mains and the venting is taken care of by the radiator vents? i imagine vertical mains would have to be 2 inches.

what i'm going to try is going over this main venting issue by timing the duration and make adjustments and see if the rest takes care of itself.

ww

i timed the short main at 1 minute and the long main at 2 minutes to get steam with vents removed. i put them back. all the radiator valves didn't get hot in 3 minutes...one branch off main got stalled at one foot in off main..i took off the cap on the pipe in the kitchen where radiator was removed and heard a sound like boiling water..no steam came out.

does anyone know the problem with this or what resources as far as books,etc will get me an answer on how to balance off these radiators and get heat to them quickly?...maybe one big one is a steam hog and taking the steam..but if so how do i stop it...small vents or something..?..

if the steam gets to the end of main..then i put the vent back on..what is the problem as to why the steam doesn't get quickly to the valves on the radiators..so get there but others really stalled. these steam pipes are 2 inch mains.

BobC

what vents are you using on the radiators? If you vent the mains quickly you usually want to vent the radiators slowly. Are the pipes from the main to the problem radiators a lot longer than others? Make sure you don't have any sags in the radiator pipes that might trap water and collapse the steam before it gets to the radiators.

Bob

Abracadabra

ww said:

i timed the short main at 1 minute and the long main at 2 minutes to get steam with vents removed

How long with the main vents on?

ww said:

i put them back. all the radiator valves didn't get hot in 3 minutes...one branch off main got stalled at one foot in off main..i took off the cap on the pipe in the kitchen where radiator was removed and heard a sound like boiling water..no steam came out.

take a pic of the takeoff from the main to the kitchen radiator. Takeoff may be pitched away from main. Is this 1 or 2 pipe steam? Why is it capped off?

ww said:

does anyone know the problem with this or what resources as far as books,etc will get me an answer on how to balance off these radiators and get heat to them quickly?...maybe one big one is a steam hog and taking the steam..but if so how do i stop it...small vents or something..?..

Are you expecting hot radiators in 3 minutes? That's a bit too fast.

ww said:

if the steam gets to the end of main..then i put the vent back on..what is the problem as to why the steam doesn't get quickly to the valves on the radiators..so get there but others really stalled. these steam pipes are 2 inch mains.

What main vents do you have installed?

ww

it took more than double the time to vent the air out with the gorton 2 and 1 on long...and hoffman 75 and gorton 1 on the short..1 pipe system..radiator removed and capped in kitchen.. i don't expect hot radiators in 3 minutes but was told the valves should be hot in a short time.

ww

ok bob, visually it doesn't look like pipes sag and i checked some with level as well..i've thought that water may be in pipes but can't locate the problem. when i fire the boiler and take the vents off...at the point the steam comes out of the end of main without a vent..and i put the vent back...isn't that fully vented at this point?..i've tried various radiator vents from 4 to d...in three of the cases the pipes go from the basement to the top floor and are longer..seems like steam goes a foot off main..and stalls there..too an hour to get steam to that radiator.

remember..i start these tests from a cold boiler with no heat on in house..and temp is like 47 degrees in house...i've asked before if the fact that the house isn't continually heated if that could be a problem with the condensation back to water and the extreme vacuum created by this.

BobC

It could be the radiators (make sure they have a little slope towards the inlet pipe) or the pipes they are connected to are sloped badly and have trapped water, if it's on the second floor it's hard to inspect. You could try lifting a radiator up by 1/2 to 3/4" on both ends to see if that changes anything.

If you are trying to come back 10 degrees , or more, a lot of condensate will be created.

Bob

Abracadabra

ww said:

it took more than double the time to vent the air out with the gorton 2 and 1 on long...and hoffman 75 and gorton 1 on the short..1 pipe system..radiator removed and capped in kitchen.. i don't expect hot radiators in 3 minutes but was told the valves should be hot in a short time.

You need more venting. Shouldn't take "double the time".

Valves shouldn't get hot until all main vents have closed (more or less).

Are all your steam mains and takeoffs insulated?

ww

ok bob...i've calculated approximately using the formulas for piping and finding out the cu ft per minute going to the radiators,pipe length and distances from mains.

i will put the vents in the radiators that came out in the calculations and see what happens with that. this is very interesting stuff to me and will see how this works. good pickup on the temperature difference and the condensation. i figured that myself too.

by trying out this mathematical calculation which i read in balancing steam systems using vent capacity i'll see if this works. it makes total sense so that radiators don't accept steam too fast or too slow..and it makes sense that it would cause an imbalance...hence the steam hog reference.. i'll try this out. thanks.

ww

things worked out better with this formula...the ones on the radiators were incorrect and imbalanced...the house was 47 degrees and the boiler was started...within an hour and a half the house was up to 60 and all radiators were hot. i utilized the formula area and divided by 3 as a start time since they suggested that in article. i'm curious as to what vents i'd use if i used different minutes...in fact i figured that out too but didn't try it yet.

this makes alot of sense and as a matter of fact the size of the radiator has alot to do with the vents in this case. it's difficult to just look at a drawing of a house and just put the vent that is suggested...it's a good start point but i like doing things like this..for me it's easier..and it worked too. i will continue to fine tune this as i go along.

the vents have to be sized correctly according to branch pipe size and length..in addition to figuring the area of the radiator...nothing that these steam experts don't know...past and present...but i'm glad i took information from various readings and was able to apply it to myself.

At the start temperature i mentioned does it seem like it took too long to heat things up from 47 to 60?

I'm just glad that I'm here with Heating Help and you all to get the help to figure things out.

ww

In the Balancing Steam article there is a chart showing maid o mist vents at 1 to 3 oz.

it seems that after looking at all the 1 to 3 oz drawings of steam systems in the articles the results are mostly only c and d vents on the radiators in the examples. this is how it worked out for me as well..will see how this works out....i hope it doesn't turn out to be another steam hog issue....and if the numbers don't lie..we'll see what happens.