Adding/Replacing Main Vents

Chuck Sorce

Chuck Sorce

Adding/Replacing Main Vents

Alright, I think I am making some progress. A careful inspection has lead me to the conclusion that my main vents are shot. (The two pictures attached show that it's probably not too hard to figure this out)

Here's my plan of attack, and where I need some help.

1. Purchasing Main Vents - I think I am going to get two Gorton No. 1, 3/8" Air Eliminators. Is this a good valve for my purpose?

2. Placement of the new vents - I think the old vents are poorly placed. Readin Dan's books lead me to believe I should have these vents about 15" before the end of the main and stood off from the main on a nipple. Is this correct? It seems this might help with the obvious water problem, and standing them off the pipe might help get the temperature of the valve down allowing it to function better. I am thinking of bring the valve off at a 45° on a 3" extension, then using an elbow to get back to vertical, 3" extension to the valve. Does this sound okay, or should I try to come straight off the top? I am assuming I should use black extensions/nipples, not brass.

3. Borrowing/Renting tools - I have never drilled into this type of pipe. I have experience machining a lot of Aluminum parts, which is really soft, but not steel pipe. Is this a handle drill project that I can do easily if I buy the correct drill bit and tap?

4. Do I need to remove the old vents and plug them? It seems that they are pretty good plugs right now. They are either functioning poorly, or completely shut.

Thanks in advance for any advice.

Steamhead

They're shot all right

Before you select your new vents, measure the length and diameter of your mains. The insulation is almost certainly 1-inch thick, and the pipe walls are 1/8", so if you subtract 2-1/4-inches from the outside diameter of the insulation you'll get the pipe inside diameter.

The vent placement isn't my first choice, but I think you'll be OK if you put the new ones up on 6-inch nipples. The existing vents look like they have 3/4-inch threads, so that's the nipple size you want.

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Chuck Sorce

Thanks for the advice. I think I'll simply try to replace the main vents at their current locations.

The vents currently installed are Dole No. 6B. Is there a Hoffman, Gorton or other replacement for these. I can't seem to find any information on this vent. I see a lot of Dole No. 1-5 vents, but no No. 6 when I do a web search. Also, measuring the thread, it looks like a 1" OD so this would indicate 3/4" NPT. I assume I'll just go with the larger Gorton that is 3/4" thread.

One of the vents is under a 2"x10", so I think I'll go with a 3" nipple - 45° - 3" Nipple - 45° (To Vert.ical) and then the valve. (All Black Parts)

Thanks for the help!

Steamhead

I think those Doles are vacuum vents

made to let air out, but not back in. This was great on coal, but doesn't work well with oil or gas firing. So you want to get standard main vents of the proper size to replace them.

Sizing these vents is crucial to quick response and fuel economy. You want the steam to reach the ends of both mains simultaneously, and this should happen in about a minute after the boiler starts producing steam. We determine vent sizes by how much air needs to be vented, this can be calculated from the length and diameter of the steam mains.

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