Boiler In A Boiler

[crshears]

Hello all,

A traction engineer I know is working up the design for a 'boiler within a boiler'; the boiler on the vintage Waterloo 14 HP Portable engine was condemned as a pressure vessel, but not mechanically, meaning it can still serve as the body for all of its attached components.

Sorry about making you cock your head to the right; the second pic reverted to its original rotation, even though I saved it as an upright view, and I don't know how to fix it...

Rather than lose the look of the original riveted boiler by scrapping it and having a new exact unity scale replacement welded boiler fabricated, the owner is looking to have a slide-in replacement boiler made for him.

Both the complete firebox and front and rear tube sheets are planned to be made from scratch, employing purchased pre-fab fire tubes; but he is looking to use an appropriately scheduled piece of 24" OD seamless / extruded steel pipe for the shell, as this should fit nicely inside the original 26" ID boiler.

My question pertains to any connections made into the seamless / extruded steel pipe; my understanding is that the native metal of the pipe cannot simply be drilled / bored, tapped, and threaded to directly receive steam and water connections, but that oversize holes will need to be bored and what I recall being called "threadolets" welded into place to accept threaded pipe. A corollary of this requirement would of course be that the design configuration of the fitting of these threaded bodies would have to be taken into account to ensure the finished new boiler will fit inside the old shell without mechanical interference.

Am I correct in my understanding?

If so, what boiler design standard in Ontario, Canada stipulates this?

Thanks.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[SnTMan]

crshears, I have no idea what Code or standard your friends' work might fall under, but I'd be surprised if a detail similar to this (from Sec VIII, Div 1) would not be allowed. A coupling, half coupling or other suitable threaded fitting set thru the vessel wall, projection such that it fits within the envelope. I'd agree that threading the vessel wall, even if permitted, is a poor detail.

What an interesting project

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

Nice ... from the days when a 360° sunroof was standard equipment.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[TBP]

There is a company called Boilersmith in Seaforth Ontario that will - among other things - build replacement boilers for such projects. Customers would ship them their traction engine boiler carcasses, and they would build identical (in external appearance) replacements to modern standards. They offered the option of cosmetic welded-on rivet heads on the exterior of the shell to provide an authentic appearance. Their web site

https://www.boilersmith.com/

shows a completed one. The boilers themselves were fully functional and code-compliant. I had a tour their shop about 25 years ago, when I lived in the area.

 

[crshears]

Boilersmith is well known in this province's traction engineering world.

There's also Bob Oliver near Austin, Ontario, who has over the years custom fabricated many of these, although to what extent he has added cosmetic rivet heads I'm not sure...



CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

Where is this unit located?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[crshears]

I believe that at the moment it's @ the Ontario Steam Heritage Museum near Puslinch, Ontario, Canada.

Why do you ask?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

Cause I am sometimes in the area (actually when I was a kid our family would go to the beach at Puslinch Lake). I didn't know about the steam museum though. When this plague subsides I'll want to visit.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Dhurjati Sen]

Before delving into "to be or not to be" few NDTs on the existing boiler as a start would help you.
Take a replica at 3/4 locations to get a feel of the microstructure.
Take hardness at 10/15 locations using a portable hardness tester.

The results would guide you to take a decision.

DHURJATI SEN

 

[crshears]

Hello Dhurjati Sen, to what "decision" are you referring?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Dhurjati Sen]

CR

If at all the material is capable enough to be drilled and / or welded.

DHURJATI SEN

 

[crshears]

Hello all,

Here's a redacted response from my traction engineer friend as a follow-up to your queries about what is planned:

Hey crshears,

Sorry for the late reply, my procrastination habit of replying to my emails is very obvious.

I found your post on the engineering website. Great post indeed.

To clarify some of my design, yes, all threaded pipe connections will need to be done via a coupling or "weldolet" as it is sometimes known. These couplings are attached to the pressure vessel with a full penetration weld. In the ASME and B51 code, you may actually have the pipe fittings threaded into the shell of the vessel, however I believe that the minimum shell thickness for this is 0.5" to allow sufficient thread engagement.... My boiler design is going to use a section of SA53-B seamless pipe which has a wall thickness of .375" There will be roughly 1" clearance between the inside of the old shell and the outside of the new shell.

So! To answer your question about the structural integrity of the existing old boiler shell: I have done some NDE on the old shell...the majority of the barrel is close to 5/16 thickness. I'm going to weld rails on the belly of the old barrel for the new boiler to rest on. In the firebox, the new boiler mud-ring is actually going to sit up top of the old mud ring still riveted in place. On these pre-1900 Waterloo boilers, the mud rings are actually 2.5" thick cast iron.

Since I have cut the back head off the new boiler already, the wrapper sheet shell is quite flexible now, seeing as it is no longer stayed onto the firebox. When I re-attach the old back head once the new boiler is installed, it will help somewhat with the rigidity... however I will also be installing 3/8" reinforcement plates on the inside of the old shell. Everything is somewhat experimental as we go...

I should mention that I am actually not the first guy in Ontario to do this... Years ago there was a fella named Ken Speers. He had a 20HP Robert Bell traction engine. He put a new boiler inside the old boiler. I am told the engine actually worked very well! That engine has since been purchased by someone in the Netherlands, but at present is still here in the province, hidden in storage. Not sure when they're planning to ship it overseas.

Seems to know his stuff...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]