Steam boiler, thickness of copper sheet.

Hi, folks!

I am planing to make the boiler for Stuart 10D, the boiler size is 105 mm diameter and 190 mm length and have working pressure at 4 kp/cm (60 PSI). I has calculated the working pressure at 4 kp/cm (60 PSI) and got answer 1 millimetre /0,039" copper with the 105 mm /4,15" diametre.

Will it be enough thick with 1 millimetre /0,039" copper sheet as boiler material with the working pressure at 4 kp/cm (60 PSI) in a 105 mm /4,15"  diametre boiler?

It is difficult to buy the large diametre tube in copper tube in Norway and the large diameter tube in copper is not cheap.

Jens Eirik

Edited By Jens Eirik Skogstad on 08/12/2012 21:19:42

Hi Jens,

See this thread: **LINK**

My copper tube is much smaller in diameter and it seems that thickness (0.042" is marginal for a boiler at similar pressure - certainly not enough if the boiler is a structural component.

I have a boiler of 3" diameter - a slightly extended Tubal Cain design and it uses 16 gauge copper, that's about 0.062"

I think you want significantly more thickness. use the calculations in that thread mentioned above and I'd expect it to come out nearer to 2mm thick.

Neil

I posted a boiler query a while ago. Which Tubal Cain book is referred to in the linked thread?

I used the formula who is recommended by K. N. Harris in the book "Model boilers and boilermaking". Is the formula good enoug to make the boiler safe in stress under working pressure and working temperature? Not tried the Tubal Cain's formula as here: thickness=pressure x diameter/2xUTS.

Jens Eirik

Edited By Jens Eirik Skogstad on 08/12/2012 22:24:31

I calculated after the Tubal Cain's formula and got answer: Cold= 0,00397" and steam at 120PSI = 0,0327", also between 0,1 mm and 0,83 mm. (I has 1 mm copper sheet)

Here is the answer...

Cold: 60 PSI x 4,15" : 2 x 3800 = 0,0327" and temperature steam at 120 PSI: 60 x 4,15" : 2 x 31360 = 0,00397"

Correct???

Jens Eirik

Edited By Jens Eirik Skogstad on 08/12/2012 22:41:33

Using Harris's formula I get 1.0mm for a 105mm tube at 60psi but gut instink tells me 2 - 2.5mm would be better

60x4.15 / 2x3125 x 100 / 95

249 / 6250 x 1.052 = 0.042" = 1mm

Some notes on your post above

I notice you are using a higher UTS than harris and you have a 10times larger UTS for 120, surely that should be less 3800 would be nearer the mark

You have got the results for 60psi and 120psi around the wrong way in the first paragraph

Using John Hainings formula I get 0.070" or 1.8mm

J

Edited By JasonB on 09/12/2012 08:20:17

I has maked a spreadsheet in Excel with K. N. Harris formula.. got answer 105 mm with 1 mm copper will have working pressure at 4,18 kp/cm, ... with 1 mm steel will have 11,22 kp/cm..

Is 1 mm wallthickness not safe enoug to use in the boiler if the answer from calculating of the thickness by diameter, pressure is correct?

Jens Eirik