Tapping Boiler shell directly
Tapping Boiler shell directly
Are there any issues with drilling and tapping a boiler shell directly without a welded bushing to add a water inlet? Probably 5/16 mtp or 1/8 npt.
Re: Tapping Boiler shell directly
Depends on the shell thickness and shell curvature and operating pressure and shell material and ??. 1/8 NPT has 27 threads/inch and I would want at least 6 full threads myself for a 1/8 NPT fitting into steel at 100psi (just a guess) Small radius shell would have a thread engagement different from a flat plate, such that you might need even more threads. Alternative to contiguous welding, you could tack weld and then braze/silver solder a bushing to get the extra threads and simplify.
Good luck,
SteveR
Good luck,
SteveR
12x36 Enco Lathe, 9x42 Bridgeport, SMAW, O/A, Miller MIG w/gas, plasma
Not enough measuring tools...
1.5" Allen Models Consolidation on air.
1" FEF in progress
1" & 3/4" LE Projects
I'm thankful that metal is recyclable....
Not enough measuring tools...
1.5" Allen Models Consolidation on air.
1" FEF in progress
1" & 3/4" LE Projects
I'm thankful that metal is recyclable....
Re: Tapping Boiler shell directly
10 inch pipe, 10 3/4 OD, sch 40.
- Chris Hollands
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Re: Tapping Boiler shell directly
FYI - this is from the Australian model steel boiler code -
Tapped holes for bolted or studded connections shall have sufficient depth to allow a minimum length of threaded engagement equal to the major thread diameter - this would be for smaller taper threads as well I'm guessing .
Tapped holes for bolted or studded connections shall have sufficient depth to allow a minimum length of threaded engagement equal to the major thread diameter - this would be for smaller taper threads as well I'm guessing .
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Re: Tapping Boiler shell directly
If it is 10" schedule 40, that means it has a wall thickness of almost 3/8 of an inch (0.365" I believe), so that is plenty enough depth to drill and tap directly into the shell for certain sizes. 1/8" NTP and 1/4" NTP will be fine to tap at that thickness, you won't have any problems with leaks or anything unless you mess up the threads somehow. Anything larger might require a bushing of some type. I've never had a problem with any of the threads that I tapped into that. Using 1/4" wall thickness, I usually weld in a bushing. I've also seen people 'build up' the surface by about 0.100" by welding, and then drill/tap a 1/8" NTP in the middle of that.
Re: Tapping Boiler shell directly
Thanks for the replies! That's what I thought but wanted to be safe. Don't have a TIG so didn't feel comfortable doing the bushing welding.
- Bill Shields
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Re: Tapping Boiler shell directly
And what do you think we all did before TIG was available?
We stick welded everything
Your pipe is more than thick enough to stick weld a bushing in place.
Having spent most of my life around industrial boilers, I have an aversion to threading directly, although I know it is a common practice in the live steam hobby world.
We stick welded everything
Your pipe is more than thick enough to stick weld a bushing in place.
Having spent most of my life around industrial boilers, I have an aversion to threading directly, although I know it is a common practice in the live steam hobby world.
Too many things going on to bother listing them.
Re: Tapping Boiler shell directly
Some quick work in Fusion - using 28 TPI straight thread.
Your case: 6 inch copper "L" type
Your case: 6 inch copper "L" type
12x36 Enco Lathe, 9x42 Bridgeport, SMAW, O/A, Miller MIG w/gas, plasma
Not enough measuring tools...
1.5" Allen Models Consolidation on air.
1" FEF in progress
1" & 3/4" LE Projects
I'm thankful that metal is recyclable....
Not enough measuring tools...
1.5" Allen Models Consolidation on air.
1" FEF in progress
1" & 3/4" LE Projects
I'm thankful that metal is recyclable....
Re: Tapping Boiler shell directly
sch 40 pipe, i would have zero issue up to 1/8 npt. plenty of meat for proper thread engagement
If it is not live steam. its not worth it.
Re: Tapping Boiler shell directly
One more caveat for this - if you're tapping pipe thread, don't tap as deep as you normally would. You want to make sure it snugs up good and tight.
SteveR
SteveR
12x36 Enco Lathe, 9x42 Bridgeport, SMAW, O/A, Miller MIG w/gas, plasma
Not enough measuring tools...
1.5" Allen Models Consolidation on air.
1" FEF in progress
1" & 3/4" LE Projects
I'm thankful that metal is recyclable....
Not enough measuring tools...
1.5" Allen Models Consolidation on air.
1" FEF in progress
1" & 3/4" LE Projects
I'm thankful that metal is recyclable....