6" boiler tube

[ausdan]

G'day all,
I'm finally going to get around and start to replace the boiler on my 5" Don Young Hunslet - Alice class. I have the plans and the condemned boiler to help and have had the drawings signed off to commence the plate work.
I will roll the 6"(152.4mm)OD x 14'13/16 (376.2mm) barrel from 3mm copper plate, question I have is what extra material should I allow for when forming the barrel, I have read and heard that for plate work extra is needed and is understandable with all the hammering around tight corners etc, but what is needed for rolling a boiler tube manually over a mandrel? Would something like this calculation be a start point.... outside diameter (OD) + (1/2 of plate thickness) x 3.14 + = ?

Or would trimming the join be fairly simple task that I need not worry too much and just add 12mm (1/2")just in case ?

regards
Dan

[Shawki Shlemon]

It all depends on how you are going to join the ends , if a but strap type joint is used , why do you need the extra , if the plate is cut square and to the correct size the ends should meet reasonably close and the but strap will cover the ends which will be riveted and silver soldered , but if you are welding it is another matter , you need to prepare the joint ends and in that case 1/2 inch is ample in my opinion , others my suggest otherwise .

[ausdan]

Thanks Shawki,
Yes an external butt strap, so that would be ideal cut the plate square using the circumference measurement. regarding the external strap when it reaches the throat plate end, the inspector has asked for a reverse flange on the throat plate, would the strap finish at this point or would the strap continue under the flange as well?

cheers
Dan

[Shawki Shlemon]

I have only done two boilers like that and I finished the strap as but joint to the throat plate flange , just ensure a good joint and well silver soldered but I suggest to ask your boiler inspector for his/her advice and don't take my word as different boiler inspectors may have different opinions .

[suctionhose]

I don't fully understand what is being said or not said here...

The developed length of a rolled cylinder is the circumference measured by the mean diameter. ie 152 OD x 3mm wall. Use 149 dia to calc the circumference which will be the length in the flat state.

Any "extra" allowed relates to the the rolling machine itself and how much of a flat remains after rolling. It has to be trimmed off after anyway. This is a bit trial an error although it does resemble the horizontal distance between rollers (on initial pinch machines)

In the case of a copper barrel, I would cut it exactly to the mean circumference and manually end-set it prior to rolling or roll and manually set the ends after.

Either way, whether wrapping it around an oxy bottle or doing it with rolls, Mean Circ is the length you have to start with.

[redmog]

Aug 11, 2013 10:58:30 GMT suctionhose said:

The developed length of a rolled cylinder is the circumference measured by the mean diameter. ie 152 OD x 3mm wall. Use 149 dia to calc the circumference which will be the length in the flat state.

I think he means 152mmOD  - 3mm = 149mm mean diameter, then multiplied by 3.142
which gives a length of the surface development of 468mm

Chris

[suctionhose]

Aug 11, 2013 11:39:04 GMT redmog said:

Aug 11, 2013 10:58:30 GMT suctionhose said:

The developed length of a rolled cylinder is the circumference measured by the mean diameter. ie 152 OD x 3mm wall. Use 149 dia to calc the circumference which will be the length in the flat state.

I think he means 152mmOD  - 3mm = 149mm mean diameter, then multiplied by 3.142
which gives a length of the surface development of 468mm

Chris

That's what I meant thanks!!!!

[ausdan]

THanks for the replies, that is what I was after some clarification for when I cut the plate.