APRIL 23, 1914| 
NATURE 
205 
developed by the combustion, and an evaporation per 
sq. ft. of heating surface nearly twice that of an 
express locomotive boiler. The combustion of the gas 
was completed within 4 or 5 in. of the point where 
it entered the tube, whilst the temperature of the pro- 
ducts leaving the tube was about 200° C. Of the 
total evaporation, no less than 70 per cent. occurred 
over the first linear foot of the tube, 22 per cent. over 
the second foot, and only 8 per cent. over the last foot. 
This points to a very effective ‘‘radiation”’ trans- 
mission from the incandescent granular material in 
the first third of the tube, where the zone of active 
combustion is located, although it should be remarked 
that the loci of actual contact between the incan- 
descent material and the walls of the tube are so 
rapidly cooled by the transmission of heat to the water 
on the other side that they never attain a temperature 
even approaching red heat. The granular material in 
the remaining two-thirds of the tube serves to baffle 
the hot products of combustion, and to make them 
repeatedly impinge with high velocity against the 
walls of the tube, thus materially accelerating their 
cooling, and either preventing or minimising the 
formation of the feebly-conducting stationary film of 
I91I we received an inquiry from the Skinningrove 
Iron Co., Ltd., for a boiler of about ten times the 
capacity of the experimental unit, to be fired by means 
of the surplus gas from their new Otto by-product 
, coking-plant, we had no hesitation in accepting a 
_ commission to install our first large boiler there, under 
a strict guarantee as to its output and efficiency. 
The plant was successfully started up on November 
7, 1911, for a month’s trial run—day and night con- 
tinuously—after which it was opened up for an official 
inspection by the representative of a Boiler Insurance 
_ Company. Everything worked without a hitch during 
this trial; steam was generated at too lb. gauge 
pressure, from a feed-water of about 4° of hardness, 
whilst the average temperature of the waste gases leav- 
ing the feed-water heater was reduced to 80° C. (say 
175° F.), a sure indication of the high thermal 
efficiency of the plant. When, at the conclusion of 
the month’s trial, the boiler was opened up for in- 
spection, the combustion tubes were found to be in 
_ good condition and free from scale; indeed, owing to 
_ the extremely high rate of evaporation, the scaling 
} 
DIAGRAM _OF THE FUNDAMENTAL BOILER UNIT 
1500 
1400° 
DEGREES _CENTIGRADE 
SFE : 
100 CUB FT COAL ¥ . 
GAS PLUS 55) 
CUB FTAIR PEI 
HOUR 
22 8 
% OF TOTAL EVAPORATION FOR EACH LINEAR FOOT 
Fic. 3.—Fundamental boiler unit. 
relatively cold gases which in ordinary boiler practice 
clings to the tube walls, seriously impairing the heat 
transmission. 
Having thus satisfied ourselves of the efficiency of 
the fundamental unit as an evaporator, we proceeded 
to construct our first experimental boiler, made up of 
ten tubes, each 3 ft. long and 3 in. in diameter, fixed 
horizontally in a cylindrical steel shell capable of 
withstanding a pressure of more than 200 Ib. per 
sq. in. The gaseous mixture was forced through the 
tubes under pressure from a special feeding chamber 
attached to the front plate of the boiler; the products 
of combustion, after leaving the boiler, passed through 
a small feed-water heater containing nine tubes, each 
1 ft. long and 3 in. in diameter, filled with granular 
material to facilitate the exchange of heat. 
This combination of boiler and feed-water heater 
proved remarkably successful in every way; its ther- 
mal efficiency was 94 per cent., with an evaporation of 
ae 21 to 33 Ib. per sq. ft. of heating surface per 
our. 
The 110-Tube Boiler at the Skinningrove Ironworks. 
Six months’ continuous experience with our first 
experimental unit gave us great confidence in its 
trustworthiness, so that when in the early months of 
NO. 2321, VOL. 93] 
TOTAL HEAT TRANSMITTED = 87% OF NET CAL VALUE OF GAS . 
TOTAL EVAPORATION = IOOLBS WATER PER HOUR FROM AND 
AT 100°C (2/2°F). 
MEAN EVAPORATION PER SQ FT HEATING SURFACE = 20~ 22 
LBS PER HOUR FROM AND AT 100°C (212°F). 
troubles experienced with other types of multitubular 
boilers appear to be completely obviated, the scale 
being automatically and continuously 
shed from the tube in thin films (about 
1/30 in. thick) as fast as it is formed; 
a very important advantage, as anyone 
who is plagued by scaling troubles will 
appreciate. An independent trial of the 
plant on July 29, 1912, gave a thermal 
efficiency of 927 per cent. 
Within the last few months the firm 
of Krupps have put down a boiler in 
connection with one of their coking 
plants in the Ruhr district of Westphalia, 
10) 
200° from the plans of the Skinningrove 
plant. This boiler has been running 
successfully since October last, and 
‘ 
PR LD A eh a => 
= 
about three weeks ago underwent its 
official steam trials, which were carried 
out by the Bergbauliche Verein. Pend- 
ing the official publication of the results 
in the German technical Press, I am pre- 
cluded from giving any details now, 
but, I am informed, that they have 
entirely confirmed the Skinningrove trial. 
I have perhaps said enough already 
about the boiler and its working 
to convince you that it combines high thermal 
efficiency and concentration of power, in a 
unique degree, and perhaps I may be permitted to 
summarise the other important advantages which may 
be claimed for it. First, from the constructional point 
of view, nothing could be simpler or more compact 
than a cylindrical shell only 4 ft. long by to ft. in 
diameter, traversed by straight tubes, supported on a 
casting, and requiring neither elaborate brickwork 
setting mor expensive chimney flues and_ stack. 
Secondly, it has a further advantage over all multi- 
tubular boilers in that the front plate can never be 
heated beyond the temperature of the water, however 
much the firing may be forced, a circumstance which, 
coupled with the extremely short length of the tubes, 
implies an absence of strain and greatly reduces the 
risk of leaky joints. Thirdly, the high rate of mean 
evaporation obviates scaling troubles, and the very 
steep evaporation gradient along each tube causes a 
PRODUCTS LEAVING 
AT 200°C. 
| considerable natural circulation of water in the boiler, 
a factor of great. importance from the point of view 
of good and efficient working; in this connection I 
may remind you that under normal working condi- 
tions we obtain a mean evaporation of 20 lb. per 
sq ft. of heating surface an hour, and can, if need 
be, force this up to 35°lb.; of this total evaporation, 
