The Steamboating Forum

There is a guy building boilers with 12" dia schedule 40 pipe is this safe? He claims the wall thickness is 3/8" thick.

I wouldn't be afraid of them as long as his welds are good.

x2 on the welds

That's about the same thickness (if not thicker) as the shell on our ASME code 3-pass horizontal fire tube (HFT) Kiwani boiler. 4-ft diameter shell, 200sq ft/hs, 150psi working pressure.

My boiler I think uses a schedule 40 pipe for the shell also. It's around .37 thick. We took it to 300 psi on the hydro, nary a creak or leak. It's 24 inches in diameter.

-Ron

12 inch schedule 40 pipe has a wall thickness of 0.406 inches, outside diameter of 12.75 inches. Same pipe with 0.375 inch wall is called "standard wall".

I built a boiler with 12 inch schedule 20 pipe, wall thickness is 0.25 inch. I hydro test at 500 PSI, and this pipe will take over 1000 psi without yielding. Schedule 40 can take even more pressure.

These pressures are only good without large un-reinforced openings in the shell, which is fairly typical of vertical firetube boilers. If you have a Roberts type boiler, with lots of holes in the 12 inch pipe, then there are higher stresses, and lower allowable pressure.

Fred,

Correcting my last post on this topic, I looked up schedule 40 24" diameter pipe and it has a .660" wall. Mine isn't schedule 40 shell.

-Ron