scale-1 inch-1 foot. Allen Engine Works.
July-1872.

Each boiler was tested by setting its damper and its steam-valve wide open, so burning all the coal that could be burned by it under its draft, and delivering freely all the steam that it made. This latter entered the condenser at the top, and the water formed by condensation was drawn off at the bottom, while the condensing water entered the tank at the bottom and was drawn off at the top, the currents of steam and water being thus opposite to each other, which was an ideal construction. The condensing water at a temperature of 45.5 degrees flowed in under the pressure in the city main and was measured in a Worthington meter, and the temperature of the overflow taken. The condensed steam was drawn off into a barrel and weighed, 300 pounds at a time, and its temperature taken. This method was an excellent one.

Not having high chimneys, no boiler had a strong draft, as shown by the coal burned per square foot of grate. Our draft was the strongest of all. Only the Allen boiler and the Root boiler gave superheated steam, and the competition between them was very close. The valve being wide open, giving a free current into the condenser, the superheat of our steam fell to 13.23 degrees Fahrenheit. Root’s superheat was 16.08 degrees.

Root’s boiler, the trial of which occupied the first day, blew steam from the open try-cock, from water at 46 degrees Fahrenheit, in sixteen minutes from lighting the fire. Next morning our boiler blew steam from water at the same temperature, in twelve minutes, and Mr. Root holding his watch could not resist the ejaculation, “Wonderful boiler!” The Allen boiler, burning 13.88 pounds of coal per square foot of grate per hour, evaporated one cubic foot of water per hour from each 17.41 square feet of heating surface. Root’s boiler, burning 11.73 pounds of coal per square foot of grate per hour, required 23.59 square feet of heating surface to evaporate one cubic foot of water per hour.

Our stronger draft, 13.88 against 11.73, accounted for 3.2 pounds of the above superior evaporative efficiency, leaving 3 pounds to be accounted for by the more rapid circulation in the Allen boiler. The great value of the inclination of the tubes was thus established. The report contains this sentence: “The Committee desire to express their appreciation of the excellent general arrangement and proportions which gave to the Allen boiler its remarkably high steaming capacity.”

The reader will observe in the [plan] of this boiler the pains taken to maintain as far as possible parallel currents of the heated gases through the boiler, and taking the flues off at the bottom, thus bringing all the heating surfaces at the same distance from the furnace into approximately equal efficiency.

RESULTS OF THE COMPETITIVE TRIAL OF STEAM BOILERS AT THE FAIR OF THE AMERICAN INSTITUTE, NOVEMBER, 1871.

Name.Square Feet.Ratio of
heating
surface
to grate
surface.		Total Weights.Ratio of
water
primed
to water
evapo-
rated.		Mean Temperatures.Total
British
thermal
units.		Total
units
per
pound
of
com-
bustible.		Apparent
Evaporation.		Actual
Evaporation.		Equivalent
evaporation
of water at
212° Fahr. and
atmospheric
pressure.		Square feet of
heating surface
required to
evaporate
one cubic foot
of water
per hour.		Coal,
lbs. per
square foot
grate
surface
per hour.		Efficiency;
actual
evaporation
of fuel
divided by
theoretical.
Grate
surface.		Heating
surface.		Coal.Com-
bustible.		Feed.Steam.Primed
water.		Injection.Feed.Water of
conden-
sation.		Discharge.Steam.Super
heat.		Flues.Per
pound
of coal.		Per
pound of
com-
bustible.		Per
square
foot of
grate
surface
per hour.		Per
square
foot of
heating
surface
per hour.		Per
pound
of coal.		Per
pound
of com-
bustible.
A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.Q.R.S.T.U.V.W.X.Y.Z.Z. 1Z. 2
Root27 876¹⁄₂32.538003185.527896 27896 0. 0. 45°.9445°.9458°.31143°.1334°.616°.08416°.632,751,834.3410,281.537.348.7686.092.657.348.7610.6423.5911.730.709
Allen32¹⁄₄920 28.553754527 39670 39670 0. 0. 45°.545°.563°.48154°.76330°.6313°.23345°.8746,387,827.110,246.927.388.76102.513.597.388.7610.6017.4113.880.707
Phleger23 600 26.128002274 20428 19782.94645.063.2645°.6545°.6554°.38120°.83321°.060°. 503°.7623,066,685.3910,143.667.268.9573.702.837.078.7010.4922.7410.130.699
Lowe37³⁄₄913 24.244003705 34000 31663.352336.656.945°.045°.054°.8131°.5319°.480°. 389°.637,228,739.07210,048.247.689.1275.063.107.208.5510.4021.639.710.693
Blanchard8¹⁄₂440 51.812321047.510152.59855.6296.93. 44°.444°.449°.49106°.14323°.750°. 221°.6711,485,777.3510,964.948.249.6999.531.928.009.4111.3433.4812.100.756

The boiler had one defect, seen in the [front view], cross-section. A straight passage 2 inches wide was given to the gases between each pair of tubes.

The boilers having all had a preliminary trial during the first week, I observed the vapor arising from the exposed surface of the water in the tank, and that this unmeasured loss of heat differed considerably in the different boilers, and was enormously greatest on the trial of the Allen boiler. I said nothing, but went down early on next Monday morning and on my way bought a common tin cup about 3 inches deep and 4 inches in diameter, and secured it in one corner of the tank, immersed to a quarter of an inch below its rim, and filled even full of water. This was completed before the arrival of the Committee, and was at once approved by them. I made it my business every day to note the fall of the water level by evaporation from this cup. On the trial of the Allen boiler only the water in the cup was all evaporated, and I had to fill it again. The temperature of the water in the cup was always 8 degrees below that of the surrounding water. It was thus obvious that the evaporation from the tank was greater than the fall of the level in the cup would indicate. The Committee considered that this should be increased as the tension of the vapors. The result was that the report contained the following item: Units of heat carried away by evaporation at the surface of the tank: