Tapping pipe for steam main (w/ pic!)

grye

Hey everyone. I need to drill and tap some threads to add a vent into the above pictured setup (if you look closely, there’s a plug, they probably removed the vent when they put the wall in). This is the last run and return. 

I know it’s not ideal for several reasons, but I don’t have clearance to add a T or pipe one in. 

My question is, is drilling and tapping a pipe as easy as ... well, just drilling into the pipe? And best place to put it? I was thinking into the elbow but the old one was at the top of the return. 

mattmia2

You could potentially get a street ell in where that plug is and pipe off of that. Maybe thread it in until it is pointing up and out at a 45 and use a couple nipples and 45's to offset to a place where you can mount a vent.

Steamhead

That plug is not in a good place. I'd leave it there and drill a new hole in the middle of the tee, large enough to thread for 1/2" pipe.

How long is the main? is it all 2" pipe?

dopey27177

The best place to drill the pipe is about 8" below the reducing elbow. I for one would not drill a larger hole that 1/4" provided that you have more than 48" above the top of the boiler.

Because the pipe is old I would install a shoulder nipple with a 1/4 by 1/2" elbow with a elbow for a vent. I prefer a Gorton #1 , Jacobus or Maid Mist elbow in that place. Before installing the
Elbow I would re-enforce the nipple with a good epoxy to secure the nipple.

zzzzjske

grye

Steamhead said:

That plug is not in a good place. I'd leave it there and drill a new hole in the middle of the tee, large enough to thread for 1/2" pipe. How long is the main? is it all 2" pipe?

The main runs in two directions (boiler is centered in the house). Maybe 25 feet in each direction? The other main has a vent, this one doesn’t. No surprise a radiator on the back of the house gets way too hot even with the smallest vent. 

Steamhead

A single Gorton #1 or Hoffman #75 on each main should be enough. Of the two, I prefer the Gorton.

JUGHNE

Steamhead, has something changed concerning the old rule of thumb of one G2 per 20' of 2" steam main?

Steamhead

That was never a rule of thumb, though some prefer to do it that way. Look at the Gerry Gill/Steve Pajek venting charts and you'll see where my numbers come from.

motoguy128

I’d tapped 3” pipe in about 5 locations on my header to add vents. Gone as large as 1/4” NPT.

Haven’t had an issue with any leaks that I can see. But I only run at <1oz pressure most of the time. Funny how all the valve steam leaks and such disappear without any DP.

Added or moved vent location in a couple radiators too. I found the cast iron radiators were almost thinner than the steel pipe. Definitely softer as expected.

grye

motoguy128 said:

I’d tapped 3” pipe in about 5 locations on my header to add vents. Gone as large as 1/4” NPT. Haven’t had an issue with any leaks that I can see. But I only run at <1oz pressure most of the time. Funny how all the valve steam leaks and such disappear without any DP. Added or moved vent location in a couple radiators too. I found the cast iron radiators were almost thinner than the steel pipe. Definitely softer as expected.

Is tapping the pipe really as simple as a tap drill bit and drilling into the pipe? Any tips? 

grye

With this? It seems simple enough ... almost too simple ....

JUGHNE

First, you need to think in pipe thread sizes, that looks to be bolt threads.

I would not tap anything smaller than 1/4" pipe size, this will handle up to a Gorton #2, more than you would need.

You need to drill a 13/64" hole for 1/4"-18 NPT (National Pipe Thread)

I have not seen a combo drill/tap for pipe sizes....I have my doubts of even the smaller ones working well.

So you drill the hole into the pipe as straight as possible, then start the tap into the hole, it is recommended to have a T-handle for the tap to maintain alignment.
A little WD-40 for lubricant on the tap, you do not want oil inside the pipe.
I get it started and turn until some resistance is felt, then back it out only part way to clear chips and then continue.
You want to keep the alignment straight and not cross thread.

IIWM, I would buy the fittings needed before tapping.
Depending upon the physical size of your chosen vent, you screw a 1/4" nipple into the pipe, the length depending upon the turning radius of your vent for clearance from the vertical drop pipe.
Then a 1/4" x 1/2" reducing 90 elbow with about a 4" riser to your vent.
Use black pipe only with good pipe tape/dope.
No dope or tape inside the pipes.

mattmia2

The comb drill/tap is not a good idea. You need to reverse after every half turn or so to break the chips you are making. I would only use the combo in production work where you could easily replace the part or you can control the conditions easily if the tap breaks or strips (although you can drill it to the next npt size and tap it for that if you strip it. If you break the tap off, they are hardened steel and very difficult to remove. Being hardened also makes them very brittle so cut a little and reverse when you feel the tap starting to twist under the torque.). Absolutely get a t-handle wrench or a socket and t handle for the tap and drive it by hand so you can feel what you are doing.

Get some actual cutting oil like Tap Magic. It has extreme pressure components that household/motor oils do not. Axle grease also works well. It will cut a lot more smoothly than with household oil. Be careful to get very little oil in the pipe since it will affect the steaming of the boiler and then you will need to skim the boiler.