"Yarrow" boiler design?

[ripslider]

A very nice chap was kind enough to lend me "model boilers and boiler making", which is a very good book indeed.

Tucked away in the middle of one of the chapters was a short discussion plus a diagram of the Yarrow boiler. If the numbers given in the book are correct, it would seem to be twice as efficient as any other boiler discussed ( the book uses a unit of "steam per unit heating surface" - most boilers get between 1-2, the Yarrow gets 4 ).

the design of the internals seem fairly simple, at the cost of a more complex - bell shaped - body.

I was wondering if this design is really 2x as efficient as most others, and if so, do the benefits outweigh the complexity in construction? Are they widely used?

Thanks

Steve

[Shawki Shlemon]

Can you post the diagram please , so that we can have a look and may learn something . Thanks.

[ripslider]

found this on wikipedia - it seems a slightly more complex version than in the book:

en.wikipedia.org/wiki/File:Yarrow_boiler_end_section_(Stokers_Manual_1912).jpg

Steve

[havoc]

More used in marine steam, together with some variants. The yarrow isn't the only one that gets such a figure. But it isn't always clear if that figure is the plain boiler or when the -often mentioned- water pre-heater is fitted.

Some other diagrams and related boilers: www.steamesteem.com/?boilers/babcock-wilcox-boiler

[dickdastardly40]

The picture in Ripslider's link shows a 3 drum boiler with 2 water drums and a steam drum similar to as fitted to HMS Belfast on display in the Pool of London adjacent to Tower Bridge.

I am very familiar with the type shown here:

www.steamesteem.com/boilers/pictures/boiler_Watertube_1.gif

As can be seen they can be very complicated, the type in my link (Y100) has a split pass gas path to adjust superheat temperature, economiser and 3 waterwalls surrounding the furnace. There are downcomers routed through the air casing to the waterwall headers from the steam drum to ensure circulation. All tubes in the boiler were rolled into the respective drum or header. The steam drum had a large amount of internal gear to separate the hot rising water from the colder feed water and the water droplets from the steam before onward to the superheater.

Lots more ad nauseum if anybody is interested.

[GeorgeRay]

The Gresley hush hush Loco no 10000 had a Yarrow boiler with two water drums and a single steam drum. This experiment was not really a success, the loco was less economical than a standard Gresley pacific. When the loco was rebuilt with a conventional boiler the Yarrow one went to the boiler shop at Darlington to provide steam for boiler tests for which it was very successful.