From napkins to fabrication VFT boiler design

[Spanky]

Ok, so i have the boiler all done in Pro-E but I'm not sure how to post it here... the only format I can save drawings in is pdf. (new to forums and their workings) Oh... XD I just remembered how to get a .jpg sorry, I'll post the picture tomorrow morning unfortunately it won't have dimensions on it so I'll just list them with the picture.

Quick question for Fred, how do you steer a side wheeler?

Josh

[fredrosse]

Posting JPG pictures is easy, you can do it directly on this forum, provided the picture is less than 250k.
A photo hosting site is needed for larger photos, so I usually resize a picture and just directly post here.

How to steer a sidewheeler? Traditionally with a rudder, although I have two in an effort to get the rudders into the wheel wash. Sidewheeler Margaret S. steers OK, but really no rudder effectiveness unless there is boat motion. My rudders also fold up, this protects them for shallow water (the sidewheeler hull only draws about 8 inches draft) as they can kick up if I get into shallow water . I can also back up to a beach and everyone can step off onto dry land with the rudders folded up.

Traditional sidewheelers did not have individual wheel control, and many have suggested that I have this feature, but I wanted the traditional setup, which has been satisfactory. There is a video about this on Boat Design Forum.

Ray Hasbrook had a sidewheeler that used a lawn mower differential for a paddle shaft, he could brake one wheel, then the other would turn twice as fast, that sidewheeler could turn on a dime.

[Spanky]

Ok I think I figured it out, had to take a screenshot but I'm going to talk to the guy who provided me with Pro-E how to do it again. I have a isometric view and a front view.

Here's the front


And the iso


The dimensions are:
Boiler shell (green) OD: 16", Wall thickness: 3/8", Height: 25 5/8"
Furnace shell (orange) OD: 12.75", Wall thickness: 3/8", Height: 14"
Base plate (pink) Diameter: 16", Thickness: 3/8"
For the tubes and tube plates (blue) I made a sub assembly and unfortunately it would not let me color the tube plates differently from the tubes.
Top tube plate Diameter: 16", Thickness: 3/8"
Bottom tube plate Diameter: 12.75", Thickness: 3/8
Fire tube OD: 1.05", wall thickness: .154", Height: 12"

There are 42 tubes spaced 7/16" from each other

If I've left anything out please let me know, I'm going to do heating area calculations as soon
as I get back from my job hunt.

Credit goes to Fred for the 43 tube idea from my original of 85 I think it was. I went to 42 though to to fit a fusible plug in the middle of the bottom tube plate.

Josh

Edit: Fixed pictures

[fredrosse]

Good basic layout. One issue, the boiler code requires that the tubesheet be placed "entirely within" the furnace and shell tubes, so your plate dimensions should be:

Top tube plate Diameter: 15.25", Thickness: 3/8"

Bottom tube plate Diameter: 12.00", Thickness: 3/8”

Base plate, 15.25 in OD, 12.75 in ID x 3/8”

Detail attached.

It appears that you plan on using 3/4 inch Schedule 80 pipe for your boiler tubes? A better choice is A178 steel boiler tubes, they don’t cost too much, and fit the boiler specifications better than most pipe. No need for such a heavy wall boiler tube, I would use 0.095, which will last many years with proper maintenance.

[Spanky]

Yes I was planning on the schedule 80 pipe, but I'll be changing that now. Also I admit that I have not looked very closely at the boiler code, thank you for letting me know about the tube plate placement.

Just a couple questions about the detail: What is the rounded square just left of the 1/8 next to the shell? And I've read a few places about "expanding the tubes in" just wondering what that is... I think that is what has been done to the tube in the detail but I'm still new to this so I thought I should ask rather than just assume.

Lawyery Legal stuff update: In talking to my good buddy, I found out that his dad is a former boiler inspector and I'm going to ask to borrow his old code book if he still has it. Also I got a reply from the boiler inspector for district 3 of WI, turns out I need to email the chief inspector now for info on the WI special vessel certification process.

I'll try and have the changed tube plate uploaded tomorrow.
And I thought I should get the basics right first before I go stabbing holes in it... Just wanted to put that here to clarify in case you were wondering where all the important stuff is.

As always thank you so much Fred, I used a few of your posts to sway my Padre. Looks like my dream may yet be a reality even if it's a few years off.

Josh

Edit: One more question for you Fred. After reading your last post I quick looked up the A178 steel tube but I found out that there is seamless and welded varieties. I assume I should use seamless but just thought I should ask anyway.

[fredrosse]

“What is the rounded square just left of the 1/8 next to the shell?” ANS: That is called a “backing ring” and is put there for welding purposes. The Boiler Code requires full penetration welding of the tubesheet to the shell, and the backing ring lets the welder use fairly high amperage welding, without any burning thru the metal, and get a weld that fully penetrates the tubesheet thickness. The full penetration weld can be obtained by making weld passes on both sides of the joint, but you would be hard pressed to find a welder small enough to get inside the shell of our boilers!

As an aside, when I was working on Nuclear Submarine building in the 1960s (height of the cold war arms race) at General Dynamics, they found several areas where welding was required but too tight for ordinary workers. The US Govt. evoked a national security rule, and commandeered all the midgets form the circus, and trained them to be welders. This was the only way to do it back then.

[Spanky]

So that's why we have so few circuses now... Curse you governmental commandeering! *shakes fist*

Jokes aside, thank you for your continuing support Fred.

I'm trying to get my hands on a copy of the BPVC so hopefully this will be my last tech question for a while. I'm altering my design, switching to a ring array for the tubes as it's much less of a hassle to make drawings for. Since I'm going to the hassle of changing all the tubes, I was wondering if it would be alright to use the 1 1/4" OD SA178 like you have in your drawing?

Thanks again

Josh

[fredrosse]

The equilateral pitch tube spacing (tube holes arranged on a grid of equilateral triangles) is the most efficient arrangement to get the most tubes within any tubesheet area. I think if you try to use 1-1/4 inch tubes that much fewer tubes will fit your boiler, you would have to go to a larger shell diameter & furnace diameter. Experiment and see what you come up with.

[fredrosse]

“I've read a few places about "expanding the tubes in" just wondering what that is”

ANS:
Boiler tubes should be expanded by forcing the tube wall thickness into plastic (permanent) deformation, which expands the tube diameter until it is a very tight fit into the boiler tube hole. This is done with a device, essentially like a roller bearing, called a Tube Expander.

The tubesheet holes are reamed a few thousandths of an inch larger than the tube Outside Diameter (OD), and the tubes inserted. The expander is then inserted into the tube ID, and the hardened steel tapered central shaft rotated, while being pushed into the tube. This action pushes the hardened steel rollers against the inside of the tube, with sufficient force to deform the tube wall against the tubesheet. The tubes are then tight, and usually leak proof.

After expanding the tubes, some use a seal weld on the joint, as shown on previous post.

Just welding the tubes into the tubesheet without expanding them first is not good practice. This is because there would be small gaps between the tube OD and the tubesheet hole, and these gaps would tend to accumulate and concentrate dissolved solids in the water. There would be no way to effectively remove these deposits, and they can cause problems at this critical joint.

When expanding tubes, the tube OD and tubesheet hole should be very clean, with no oil or other coating, just bare clean metal. The tube expander should be dipped into a can of oil and fully submerged to lubricate all of these parts during the expanding process.

[fredrosse]

“The A178 steel boiler tube, found out that there is seamless and welded varieties, select seamless?”

ANS: The seamless is somewhat better, but the welded boiler tubes are very adequate for the service at a few hundred PSI or less. I would guess 98% of the A178 tubes sold are not seamless, and the seamless ones must cost plenty compared to the welded tubes (ERW). My boilers use ERW tubes.