Drilling and tapping a main

cn30

I need to drill and tap a 1 ½” main to put in a vent; there are no plugs, no T’s, nothing, and old rusty pipe.



My question is, how small a hole can I drill and tap and still get decent venting? I ask because I’ve read that a Gorton D, at 1/8” (or ¼” straight), vents as much as a Gorton 1, with a ½” connection. Is that accurate? Is it all the orifice size? If so, why have such large connections?



If I can tap for ¼” I can get 18 threads per inch, or 27 threads per inch at 1/8”; given that the 1 ½” main is somewhere around 3/16 to .20 inches thick, but is curved, I could get at least 3 threads cut for a ¼” tapping, and maybe 5 for a 1/8” tapping. I would do the latter if I trusted that I would get adequate venting.

BobC

A 1/8" pipe . . .

has the capacity of more than 3 Gorton #1's (1.2 cfm vs 0.33 for a Gorton #1 or D). This info comes from the Gill & Pajek venting capacity chart that is sold on this site.



Bob

Hap_Hazzard

No fittings?

I'm having trouble imagining this. What's at the end of the pipe? I know the pros do this kind of thing occasionally, but getting a drill into the top of a steam main, dead center and perpendicular, is no mean feat. And the best you can hope for is almost 4 threads @ 27 threads/inch because 1 1/2" schedule 40 pipe is only .145" thick, and we don't know how much of that is rust. I'd be looking for a fitting.

cn30

fittings

The end of the pipe has a T for a takeoff to an elbow w/ riser for a first floor radiator; the rest goes to an elbow into a pipe leading to the dry return. Even if it was all brand new, it seems to me you would have to disassemble the system from the radiator backwards, since everything is screwed into something else. And it's not new--the building is 110 years old and maybe the system too.



I don't see why you would need to drill dead center into the top of the main. I was thinking at 45 degrees off vertical or maybe close to 90. It would drain any water, and with a couple of elbows you can make any angle vertical for a nipple and vent.

Abracadabra

Adding vents

Proper way to add vents to a main:







http://www.heatinghelp.com/forum-thread/139477/Location-of-main-vent#p1252588

gerry gill

you could also weld

a thread-o-let onto a hole in the pipe and have a full size tapping that you could then do whatever you wish with. Its actually the best solution as it would let you add four or five gorton #2 main vents to the main on a manifold.

Hap_Hazzard

I didn't mean top dead center.

By dead center, I mean perpendicular to a chord of the circle, if you know what I mean by that. The drill also needs to be perpendicular to the long axis of the pipe. It's not easy to get both dimensions right.



Do you have a good source for 1/8" elbows? I discovered that my local Sears Hardware has an amazing selection of small (1/8" to 3/4") brass nipples and fittings at very reasonable prices. The ones I've found at the big box stores tend to be machined rather than cast, and they much more expensive.

Gordo

That is a

really nice weld.  

gerry gill

thanks Gordo

it was the first time i struck an arc in 24 years..i sent the picture to my buddy who was a senior chief in the navy who specialized in weld inspections..he tore it up but we laughed in the process..i knew he would, and i knew i no longer had 'navy' quality skills..but hey i was at least still able to do it..actually it was your prior thread response that prompted me to get a baby weld machine and get back into it, so thanks!!

cn30

threadolet

Thanks for the suggestion, Gerry. Is the bottom of it curved to match the curvature of the pipe, or does it sit in a larger hole prior to welding? Also, the hole looks threaded--is that an optical illusion or did you try that first?

gerry gill

The thread-o-let

is curved to match the pipes contour and is also beveled in so that there is a groove for the weld..The hole was drilled with a Lennox step drill which makes a little bit of an illusion that there is a thread there..its just a hole..and a sharp step drill went thru the pipe like butter.

Gordo

Admirals and Chiefs

The smart Admirals know that it is the Chiefs that really run the Navy!



It takes a real SOB ( esp. busting someone's chops about their welding).   I sleep better at night knowing they're out there.



I once told a retired Chief what pressures I run my boilers at.

He grumped at me and said, "That ain't  Real Steam. Tha's just a frackin' LEAK!"



"Well, Chief, my job's easy. I only have to heat the building, not make it move."



So here's to heating buildings with LEAKS!  (-and making sure buildings DON'T move).



And you are most welcome, Gerry.

gerry gill

oh, thats to funny!

I got tears in my eyes from laughing.. i can just see that in my head..we didn't even take steam seriously till the line fed something that needed steam over a 150 psi..we ran the boilers at 1275 psi, so the new guy fixed the 150 and under pipes..we figured no one would get hurt on a 150 line..all perspective i guess..thats funny tho..i called an admiral 'skipper' once...ah yes, in the dog house...nothing like memories!

Hap_Hazzard

All my dad ever learned in the Navy was...

If it moves, salute it. If it doesn't, paint it.