Tornado

I can remember during my apprenticeship in the early 1960s being given a job of turning some monel bolts. They came up nice and shiny but when I asked what they were to be used for, the designer gave me a peculiar look and just turned away, much to the amusement of the foreman. All very hush-hush!

If I remember rightly monel was used in areas of high mechanical and temperature stress, particularly in applications where it would be difficult to access the component for maintenance. The LMS used them for flexible stays in fireboxes.

I do wonder whether the problems with 'Tornado''s boiler has more to do with trying to convert a riveted boiler design to a welded one rather than the issues of competance with the boiler designer. Perhaps the A1 Trust were too insistant on having a welded LNER boiler and they would have been better off either with a completely new design or just repeating the original riveted design.

Regards

 

Oh dear. If we're going to correct someone for misspelling copper, perhaps we should try and get Meiningen correct to start with.

 

When steam ruled the railways, there were 'proper' engineers and engineering was more of an art than a science. If it looked right, it generally was right. Loco boiler design evolved, from Trevithick, through Stephenson and Belpaire to Player. As things got bigger the quest for weight saving got greater and components were generally made smaller/thinner until they started to give trouble so most design ended up being a case of repeating what was known to work, within the overall restrictions imposed by the loading gauge. The first principle in boiler design is to make it strong enough so that it won't explode and that gives you the basis for stay diameter and spacing. All other things are secondary, although they may be very important. In terms of stays, they have to withstand the bending stresses imposed by unequal expansion of the two plates and the fatigue reserve factor necessary to withstand the repeated stress fluctuation. You could make them large enough to withstand that but I doubt that the associated platework would last long without problems. Within reason, the smaller diameter and longer a stay, the better in this respect, which is one reason why my earlier post made comment about the different welds and clearance holes. A fillet welded stay in a clearance hole is effectively longer than an equivalent J prep in a close fit hole (but the former can bring other problems to the fore). Whichever is chosen, one thing that should always be done is to radius the hole on the water side to eliminate the sharp edge stress raiser. Ideally, stays should be pin jointed but I don't know of any firebox stays that have been like this. Even flexible stays are effectively a propped cantilever.

 

That's not in my dictionary, though :humble:

 

Give the dictionary froth a rest Ian!

 

Well yes, youve just passed by/off an outline by one of the UK's senior and highly respected steam locomotive engineers!

Mike[/QUOTE]

Well I missed that. So is finite element analysis now used or not? If not, how are boilers designed (I am just interested in the basic method - not the detailed maths). I know about ASME - International Boiler and Pressure Vessel Code. Is that used for UK locomotive boilers?

 

Had a look at my notes from an IMechE lecture given by David Elliott back in November - the broken stays suffered from low frequency fatigue cracking, basically the inner firebox is trying to expand 1.6mm more than the outer firebox (I might have written that down wrong, it seems a bit too precise). He mentioned that the A1SLT were going to commission an FE study of the firebox to determine the exact nature of the low frequency fatigue.

Regards,

Dan

 

At least I was consistent! Come on Steve - you must remember Moors Herald - the only mis-spellings were words not in the spell checker but that didn't mean the word used was the one I meant to use!

 

I've just done some rough calcs using on-line data for Coeff of Expansion of steel (13x10-6 m/mK) and Steam Tables - water @ 250 psig = 207degC.

Making some gross assumptions about actual inner and outer plates regarding temperature - assume the outer plate is perfectly insulated and therefore at the boiler water temperature of 207 degC. The inner plate I assumed to be half way between a nominal firebed temperature of 600degC (is this anywhere near?) and the water temperature i.e. ~400 degC.

Assuming a firebox length of 2m, then the differential expansion of around 5mm horizontally is predicted. This does seem a bit extreme, so perhaps your 1.6mm is correct.

Iain

 

Well its the right ball park anyway. There is certainly a lot of engineering analysis going on behind the scenes to try and get a long-term solution tot he firebox problems. Obviously the cracking issue has added a further dimension to this work.

Regards,

Dan

 

This could be an under estimate. Red, orange or yellow flames indicate a temperature of 1000 to 1200 degrees F (500 to 600 C), a brilliant red fire 1800 deg F (1000 deg C), and white hot 2000 to 2500 deg F (1100 to 1400 C).

No doubt the raising steam process has been conducted gently. Consider this as a scenario. Tornado is at Bounds Green and coupled to its train which is drawn in reverse by a Diesel to Kings Cross station - no real effort so far. However, when Tornado sets off, bearing in mind it is tackling a 1 in 107 gradient with the exhaust draught coming into play, there has to be a rapid rise in temperature of the fire affecting the inner firebox. This does tend to negate the slow steam raising process.

That said, my gut feeling is that that there is something seriously amiss somewhere in the design/workmanship/materials area. Was the steel correct specification? Was the selected specification really suitable for the job? What design and construction experience does Meiningen have? I suspect not a lot.

I see that they recently supplied a new boiler to Australia for a C38 Pacific - hope they don't have similar problems.

We've got an ex SAR Class 25NC at Quainton with welded steel firebox - did South Africa have these sort of problems with these boilers?

I believe that much earlier in this thread I wrote of my reservations of several aspects of Tornado's boiler after seeing it at Darlington, but didn't expect the current problems.

Maybe there is something to be said after all for our old-fashioned 'little Englander' method of knocking boilers together with rivets complete with a copper firebox after all.

 

I don't have any figures for an A1 but I do have firebox temperatures for a number of locos on test (the maximum being an Ivatt Atlantic) which gives a firebox flue gas temperature of 1231°C. Tests carried out on a B1 gave a maximum firebox wrapper plate temperature of 325°C but this was with a copper firebox. A steel box will have a lower thermal conductivity but will be thinner (no idea how thick 60163's box is) so a similar figure would give a ball park answer. However, this maximum temperature will almost certainly be on the crown in the front third of the firebox. Max tubeplate temperature was recorded at 384°C, which will be the hottest part of the firebox. Sidewall temperatures will be less, but I don't have any data for this.
Whether these temperatures are applicable to 60163 as a practical design basis, I don't know. BS 2790 (the nearest applicable standard) gives a design figure of 325°C for firebox plates.
In doing your calcs, remember that firebox expansion is both three-dimensional and constrained, so it isn't as simple as comparing the expansion of two otherwise similar strips of metal at different temperatures.

 

It was a joke for heaven's sake, hence the smiley. :frusty:

 

I hadn't heard that it had *failed*. Being a bit liberal with the old language here aren't we? And perhaps unwisely so: "Tornado boiler fails: ban these dangerous contraptions from our railways" is just the sort of headline that appeals to a certain kind of "journalist"...

 

I've just heard that the boiler has been found to have a production fault (???) and is to go back to Meiningen ! any updates.

 

We should assume that the A1 lads have a decent warranty, guarantee, or whatever.

 

given the ammount of re staying that they have had to do and other problems that they have experienced everything does point to a production defect , cant the A1 lads get the work done at crewe under contract and the manufactorer pay rather than have to lift the boiler and send it back to Meiningen at least then the work needed can be assessed by someone separate from the owner or the builder after all, as has been said before, we as a country are used to all steel fireboxes and as its a british outline boiler, would the germans have been able to understand the design specifications they are used to different methods of engineering and constuction that might be the reason behind why things appear to have gone wrong