Yarrow Small Tube and Large Tube Boilers
Frontal elevation of Yarrow boiler. Enlarge
The Yarrow boiler is suitable for supplying steam to triple-expansion engines of about 650 indicated horse-power. It has 1,250 square feet of heating-surface, and 28 square feet of area of fire-grate. The external dimensions are:--7 feet 2 inches broad, 9 feet 2 inches long, and 9 feet 8 inches high, from the under-side of the ash-pan to the top of the uptake, or base of funnel. The steam-chamber is 32 inches diameter and 9 feet long. The water-chambers are 7 feet 6 inches long, 13.5 inches wide, adn 6 inches deep. The weight of the boiler, including the casing and mountings, is 5 tons 10 cwts. when empty, and 6 tons 12 cwts. including the water. When used in combination with triple-expansion engines and forced draught, the weight of the boiler, including water, casing, furnace-work, and mountings, is approximately equal to 22 lbs. per indicated horse-power of the engines.
When supplying steam to triple-expansion engines, 2 square feet of heating-surface are usually provided in this boiler per indicated horse-power; and 50 square feet of heating-surface are provided per square foot of the area of the fire-grate for a moderately strong forced draught, burning about 54 lbs. of Welsh coal per square foot of the area of the fire-grate per hour. For natural draught, a consumption of 18 lbs. of coal per square foot of the area of the fire-gratre per hour, 5 square feet of heating-surface are generally provided per indicated horse-power; and 45 square feet of heating-surface are provided per square foot of the area of the fire-grate.
The Yarrow large tube type of steam-boiler is of similar construction to that shown, but the tubes are 1.75 inches diameter. A boiler of this type is suitable for supplying steam to a triple-expansion engine of 1,000 indicated horse-power, and has 55.5 square feet of area of fire-grate, and 2,896 square feet of heating-surface, the proportion of heating-surface per indicated horse-power being nearly 3 square feet.
The external dimensions of the boiler are 13 feet 10 inches broad, 11 feet 3 inches long, and 15 feet high, from the underside of the ashpan to the top of the uptake, or base of the funnel. The steam-chamber is 4 feet 2 inches diameter, and 11 feet 6 inches long. The water-chambers are 11 feet long, 2 feet 6 inches wide, and 1 foot 11 inches deep.
This type of boiler will stand a powerful forced draught. In an evaporative test of the boiler, 19.7 lbs. of coal were burnt per square foot of fire-grate surface with forced draught, and the mean quantity of water evaporated, as from and at 212° Fahr. per pound of coal, was 10.5 lbs. for 30 hours, and 11.05 lbs. during the last 8 hours of the test.
The weight of this boiler, including water, and also the uptake to the armour deck, is about 30 tons. A cylindrical marine return-tube boiler of the same power weighs about 50 tons, hence the saving in weight effected by using the water-tube boiler instead of a marine return-tube boiler is considerable.
Source: Walter S. Hutton, Steam-Boiler Construction: A Practical Handbook (London: Crosby Lockwood, 1903).
One of the signal early installations of the Yarrow was in the destroyer Hornet of 1893. For comparison purposes, the sister-ship Havock was equipped with locomotive boilers. The Hornet won the competition hands down, with more power at a lighter weight. -- Ed.
Some Yarrow Photos
The classic inverted "V" shape of a Yarrow tube assembly; the water drums run along the lower edges, collector at top.
Head-on view of a completed Yarrow boiler, with casing removed.
The Yarrow shop proudly photographed these boilers fabricated for the Chilean dreadnought Almirante Latorre c. 1913. She sailed with the Royal Navy as HMS Canada through WWI before reverting to Chilean ownership and becoming their flagship through 1952. The uptakes to the funnels are shown in place, indicating this flat of boilers was ready to lift into the ship. Babcock and Yarrow remained the preferred boilermakers to the British service until the late 1920s, when the Admiralty type boiler was developed, closely based on the Yarrow.
Yarrow boilers were a long-time Chilean preference. They were specified for the 1902 battleships Constitución and Libertad which were contracted to British yards. The two were disowned by the Chileans when nearly complete and instead taken over by the Royal Navy as HMS Triumph and Swiftsure. The latter is shown above conducting target practice in the South China Sea, 1913.