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Post by gall335i on Sept 21, 2011 15:28:23 GMT
Hi all,
i'm looking at making a steel boiler for my 7 1/4 gauge hunslet.
i will be redesigning the drawings from a copper to steel boiler drawing! but when i spoke to the supplier of the boiler tube/plate he's told me that it's against the law to sell a steel boiler which dose not have a CE mark on it!
Does any one have any more info on this before i spend my money on the materials??
many thanks
Andy.
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Post by Blue Peter on Sept 21, 2011 19:21:37 GMT
HI
As I understand it, it is commercial boilermakers that must put a CE mark on the boilers they sell. An amatuer isn't allowed to do this, that would be illegal. If you make your own boiler, then you should have the design approved by a boiler inspector before construction, and at every stage to final steam test in order to obtain certificates, including the welding by a certified welder. Without this you won't get insurance. If at a later date you decide to sell it then I don't think anybody would buy it without the certificates, I wouldn't, certainly more important than a CE mark.
Regards
Peter
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Post by daveburrage on Sept 21, 2011 20:06:15 GMT
Redesigning a copper boiler for manufacture in steel must be very near to designing a boiler from scratch.
I think you'll have to show a full set of calculations. It may have to be submitted to Northern or Southern Federation Boiler comittee for approval. That's what I was told my my boiler inspector - and that was just a respacing of a few stays.
regards
Dave Burrage
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Post by gall335i on Sept 21, 2011 20:20:41 GMT
yeah i've spoke to the inspector at the club, i'm going to redraw the boiler with the suitable changes and he'll look over it for me and give me the go ahead!
i'm going to be making the whole boiler from 1/4 thick plate/tube which is more than enough for the pressure of the boiler to corrosion factor!!! the copper boiler is designed to be 4mm outer with 3mm firebox so 1/4 is more than enough using the formulars that are out there!
should have it drawn by next time i see him so will see what happens!
thanks
Andrew.
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Post by Blue Peter on Sept 21, 2011 21:05:19 GMT
Although steel is three times stronger than copper you have to allow for corrosion. With that in mind, the Ausie code demands a minimum 6mm thickness for barrels up to 300mm dia. For tube plates it demands 12mm. It would be a good idea to get a copy as it covers every aspect of boiler construction. It's a pity there isn't a similar set of codes in Britain.
Regards
Peter
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Post by gall335i on Sept 21, 2011 21:53:39 GMT
the barrel is only 7 inch OD with a working pressure of 100psi! 7 inch od x 1/4 wall thickness works out to be suitable for around 120psi! this takes into account for the corrosion allowance!
the formula i used is from John Haining's book- introducing model traction engine construction.
D X W.P X F
P = ----------------------
S X 2 X R X C X T
P = Plate ( barrell) thickness in inches
S = Ultimate tensile strength in IBS per sq inch / 60000
F = Factor of safety of from 6 to 10 ( usually 8 )
R = Riveting allowance ( .8 for welded, brazed or silver soldered )
D = Dia of barrel in inches / 7 inch dia
C = Corrosion allowance ( for steel only ) 1/4 thick and below = .5 to .8
T = Temperature allowance ( copper at 400f = .7 / copper at 212f = .87 )
W.P = Working pressure in Ibs per sq inch / 100psi
using this formula gave me a thicjness of just below 1/4 inch!
andy.
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Post by gall335i on Sept 21, 2011 22:59:54 GMT
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Post by ettingtonliam on Sept 22, 2011 13:33:07 GMT
Use John Haining's book with care, its getting a little dated now. I seem to remember it dates from a time when you didn't need a coded welder for a steel boiler.
!/4" wall thickness for a 7" barrel at 100 psi seems on the light side to me. I built a 4" Tasker tractor a number of years ago, which would be about that size, and I seem to remember the barrel was thicker than that. The firebox plates certainly were. Don't forget that with the firebox, you are getting corrosion from both sides of the plate, the fire side and the water side.
Richard
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Post by fostergp6nhp on Sept 22, 2011 18:06:15 GMT
IIRC the steel plate thicknesses now on a 4" Foster TE boiler for 110psi are 9.5mm barrell, 10mm firebox sides & doorplate, backhead, firebox outer sides, throatplate, 12mm tubeplates.
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Post by gall335i on Sept 22, 2011 18:40:35 GMT
surely there's a difference between locos and traction engine as traction engine boilers are the chassis which takes all the stress from the motion and from the load thats behind the engine where as the locos boiler sit on frames which has all the motion and loads placed on them.
a 4 inch scale foster is likely to have a 9/10 inch dia boiler so will need to be thicker!!
andy.
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Post by fostergp6nhp on Sept 22, 2011 20:02:39 GMT
10" no difference as regards corrosion. Also steel boilers have expanded tubes hence the thick tube plates.
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Post by jordanleeds on Oct 9, 2011 14:20:46 GMT
Is it not worth going beyond 100 PSI ? having driven a few hunslets a degree of super heating if it could be fitter would be a welcome development i would suggest pushing it to 120 PSI with a superheater
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Post by weldsol on Oct 10, 2011 13:48:55 GMT
Hi Andy
Couple of questions for you your pipe you say is 7" od it s not shown on my pipe shedule for ASME / ANSI the nearest is either shed,40 6" 168.275 od with nominal 7mm wall or shed 20 8" 219.075 with nominal 6.3 mm wall.
Also it should be grade ASTM 106 grade a or b.
The plate material should be BS1501-224-490B
Stay material should be BS EN 10025 S275JR with a 3.1 test certificate
Welding electrodes ( if MMA is used) should be E7018 (low hydrogen) and have a test cert
Paul
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ewal
Part of the e-furniture
Happiness is a good wife & a steam engine.
Posts: 293
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Post by ewal on Oct 10, 2011 14:35:34 GMT
My boilers were 10mm for the barrels & 12.5mm for the plates. All marine of course.
E.W.
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Post by parker3 on Oct 11, 2011 11:16:06 GMT
Welding electrodes ( if MMA is used) should be E7018 (low hydrogen) and have a test cert Paul Hi, As an model maker who has taken more tests for welding that I can remember but have been retired for quite a number of years, how could I now obtain a test cert.?. |
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Post by weldsol on Oct 11, 2011 13:11:45 GMT
Welding electrodes ( if MMA is used) should be E7018 (low hydrogen) and have a test cert Paul The test cert, mentioned was for the electrodes this is obtained when you purchase your electrodes just ask for a test cert. If you mean a welder qualification cert, then please PM me Paul |
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