Builder's plate from a Hawthorn Leslie triple expansion engine, 1899.
The Triple Expansion Reciprocating Steam Engine:
Its Application in Warships (1887-1945)
The diagram at left illustrates the basic concept of the triple expansion marine engine, which introduced a new level of reliability into steam engineering in the late 1880s, being universally adopted by all the world's navies within a few years. High-pressure steam (red) is admitted to the smallest, high-pressure (HP) cylinder, exhausted into the steam chest for the intermediate pressure (IP) cylinder (orange), which in turn exhausts it to the low-pressure (LP) cylinder (yellow/blue), whose enormous piston allows the depleted steam to do a last bit of work pushing a large area before being recycled back to the condenser, to be boiled again and recirculated. The driving rods and valve rods, all attached to the same crankshaft, keep the valves opening in synchrony and the whole complicated assemblage spinning away with considerable noise and vibration.
First introduced in the late 1880s, as an elaboration of the compound or double-expansion engine, triple expansion engines offered improved efficiency: More miles or greater speed -- or both -- from the same amount of fuel. HMS Victoria of 1888 and her sister, the Sans Pareil, were the first British battleships to be purpose-built with triple expansion. Although these ships were problematic in other respects, the excellent performance of their engines, and those installed in the contemporary Mersey class cruisers, made triple expansion the new standard. Indeed, the increased power and fuel efficiency of the triple expansion design made possible the larger and more seaworthy battleships of the pre-dreadnought era.
Engines for heavy battleships and vast ocean liners were among the largest built. The very largest, in fact, were constructed at Harland & Wolff's Belfast works for the White Star liners Olympic, Titanic and Britannic. These ships' gigantic machines stood more than 30 ft (9m) tall from the floor plates and weighed over 1,000 tons each. Using steam generated in 29 gigantic boilers at a working pressure of 215 psi, the engines developed 15,000 ihp at 75 rpm, driving the mammoth ships at 22.5 kts. Footage of the mighty engines turning is generously featured in the James Cameron movie Titanic; in that disaster, as in many maritime and naval sinkings, the entire engineering staff perished, hewing courageously to their posts until the last. Engine rooms in battleships were seldom the spacious affair seen on screen in the movie, however; such space was only available on record-breaking 45,000-ton floating palaces, not on warships -- even on dreadnoughts. More good views of the triple expansion engine in action and repose may be found in the Steve McQueen classic "The Sand Pebbles" (1966) in which McQueen plays Jake Holman, the loner chief engineer on an ancient gunboat cruising the Yangtze and its tributaries in the 1920s. The engine used for this movie was the heartbeat of a WWII Liberty ship; it may be viewed by the public on board SS Lane Victory at San Pedro, California (Port of L.A.). Of course, the father of all engine room footage is Sergei Eisenstein's "Battleship Potemkin," a Lenin-era silent propaganda film about the 1905 mutiny, featuring dramatic B&W footage shot aboard a contemporary of the Potemkin's in the early 1920s. More triple expansion footage can be found on our Online Movies page, along with paddle engine and Ericsson vibrating lever engine foootage.
The hot, piping-packed spaces of the engine rooms in this era vibrated to the rattle of rods and eccentrics, and the deep rumble of the propeller shafts turning in their bearings. The numerous shafts and connecting rods in the engine operated the valves in sequence to power the engine, as shown in the animated diagram at top of page and called out in our Liberty ship diagram. The continuously pumping rods threw off a fine spatter of oil which got onto and into everything. When running at speed, the increase in noise and vibration was terrific, while the bearings had to be constantly splashed with water to cool them. As a result the engine room became a wet, steamy, noisy, rather chaotic space which was likened to a snipe marsh in a thunderstorm. Voice tubes to the bridge could become unusable because of background noise, making the engine room telegraph (above right) with its loud annunciator bells the only reliable means of 2-way communication with command. Retired Scots engineers were stereotyped -- not without reason -- as all being hard of hearing.
Engines for HMS Triumph at Armstrong's Elswick works, 1901. Twin 6250-HP engines propelled the 475-foot battleship at a reliable speed of 19 kts from her commissioning in 1902 until her fiery demise off Turkey in May 1915. When installed in the ship, the shape of the engine would become less apparent as a grating would be installed at the cylinder head level, just above the top row of gauges, to provide access to valves and controls for other equipment in the engine room. The rusted, but still monumental, remains of the Triumph's twin engines may be glimpsed to this day on dives to the wreck off the coast of Turkey. The engines of HMS Majestic, also sunk off Gallipoli in 1915, are not so accessible since the vessel turned turtle while sinking, landing on her masts and eventually settling weather-deck down on the bottom as the masts snapped under the weight. Engines of HMS Hood of 1893 were visible through holes in the hull plating at her grave outside Portland Harbour, where she was scuttled in 1914; but divers report the wreck has been collapsing inward and losing the integrity of its original structure in the past 20 years.
Above is a model of a four-cylinder triple expansion engine (click here to enlarge). In this variation, there were two LP cylinders each feeding off the IP cylinder. This reduced the bore of each to a manageable size for such a large engine. Although after 1905 all the most important navies switched to the Parsons steam turbine for their ships which needed the best speed and power, triple expansion engines continued to be used for most everything else. In reality, by 1905 triple expansion engines had reached their limits for high-speed, high-performance manuevers and needed a lot of adjustment and maintenance when performing near peak. This was particularly evident with torpedo boats and destroyers, which competed for speed records on their trials, but often proved unable to perform reliably at speed for long. With the relatively low cost of a TB, it was often more opportune to produce a new boat with new technological fixes incorporated than to keep last year's speed champion in tip-top shape. Had there actually been a big-power naval war during this time, the story might have been different.
Above, control platform for the engines of the USS George Washington, twin quadruple expansion machines manufactured by Vulcan Werft, Stettin, Germany in 1909 for the initially North German Lloyd liner. Control wheels, gauges and levers are arrayed around the stout pillars of each engine. Like many of her fellow German passenger ships, "Big George" was interned at New York at the start of WWI and was taken over by the Americans in 1917 for conversion to a transport. Restored for civilian use after assisting in the repatriation of U.S. troops, she sailed for the United States Lines as a passenger ship until 1931. After conversion to oil-fired boilers and turbine engines, she became a transport in the Second World War also: In 1943 her trooping duties took her around the globe. Laid up in 1947, the 42-year-old liner was damaged by fire and then scrapped starting in 1951.
Special Literary Feature
The ingenious complexity and magnificent structure of the triple expansion engine was the inspiration for some rather fine literary efforts. We proudly present excerpts from the engine writings of Richard McKenna for the general appreciation and enjoyment.
Introduction of the Turbine Engine (1899-1910)
Above, an early Parsons turbine ad (circa 1906) flogs comparative performance statistics between HMS Amethyst (dotted line) and her piston-engined sister ship. Amethyst was built at Elswick, 1903; displaced 3,000 tons and maxed out at 22½ knots; fought at Gallipoli and was sold for scrap in October 1920. For an enlarged and more legible copy of ad, click here.
Reciprocating engines required constant maintenance because of their many moving parts, friction points, and relentless vibration; generally they could only operate at high speed for short sprints. By contrast, turbine engines, with far fewer moving parts and little friction, performed like a champion at continued high-power demand; but early models were much less efficient at lower revs.
The Turbinia zips through the naval formations at dizzying speed. Enlarge Chevalier de Martino
In order to dramatize his invention as an idea whose time had come, Sir Charles Parsons hijacked the pomp and circumstance of the 1897 Spithead Review -- held in honor of Queen Victoria's Diamond Jubilee -- with a prank that has been the envy of practical jokers ever since. Piloting his tiny turbine test-bed, the Turbinia, Parsons raced up and down the rows of anchored ironclads, making a shambles of the event's stodgy protocol. Three times Turbinia tore through the review at speeds approaching 40 knots, her bow at full plane, trailing a 30-foot plume of flame and generating a terrific wake. Not even the Royal Navy's fastest torpedo boats could catch her to enforce the decorum the day demanded. Point was made: the Prince of Wales signaled Parsons to come alongside the royal yacht. Parson's theatricality opened the door to cordial discussion of the turbine and its possible applications in the Queen's fleet. Naval officers who had pooh-poohed Parsons' radical ideas, were shocked into paying attention to them after this very public proof of concept.
It wasn't long before Parson's erecting works was busy with orders for the British navy. Turbines were first adopted with notable success in British destroyers, the first of which went into service two years after the Jubilee disruption. HMS Viper's 36-knot speed smoothed the way for a massive and daring (because hitherto untried) application in battleships. The first battleship to rely on turbine engines was HMS Dreadnought of 1906. In the same year, Cunard inaugurated service by its 27-knot Atlantic turbine liners, Mauretania and Lusitania; all of these Parsons-powered vessels were accounted a brilliant success. Few engineering officers lamented the shift to turbines, for it brought a distinct improvement in their working conditions. Gone were the pools of standing water, the hiss of exhaust steam, the perpetual grease in the air and the pounding vibration of piston and crankshaft, replaced by a less colorful but far calmer ambience, with only the whine of the turbines whirling in their massive pressure casings to remind one of the business of the station. But in many foreign navies, including the USN, the familiar racket of the rods and rumble of the crankshafts remained common right through WWII on dreadnought battleships such as the USS New York and Texas, built before WWI when the navy's imperial mission demanded greater range and fuel economy than turbines of the time could deliver. It should be noted that the four-cylinder triple expansion engines on these vessels performed up to expectations over their long careers. With adequate maintenance, these engines were quite dependable, though they could not deliver the sustained high speeds that were commonplace for turbine engines.
Further, there were many problems with producing turbines proficient at low enough rpm's to be efficient with the propellers of the day. The screws were all directly shafted to the engines on these ships. The solution was found just before WWI: the introduction of reduction gears between engine and shaft, allowing the turbines to perform at high rpms (their greatest efficiency) and propellers at theirs (generally under 100 rpm). Prewar industry was not up to producing the numbers of precision gear sets needed, however. So the geared turbine option did not come into general acceptance until the 1920s. Another option exploited by the U.S. was turbo-electric drive. This scheme worked well in six U.S. dreadnoughts built during WWI and the early 1920s. Turbo-electric propulsion had the advantages of rationalizing propulsion system layout and allowing more extensive watertight compartmentation.
Coal-Burning Technology and the Shift to Oil
The abandonment of the triple expansion recriprocating engine by the top flight of the world's navies, however, did not put the engine out of use. It had already had nearly as salubrious an effect on the world's commercial fleets as it had had on the navies in the Nineties. Triple expansion engines continued to power all manner of craft from steam launches to 450-foot freighters, Coast Guard cutters, tramp freighters, screw ferries, and river craft around the world. Before the widespread application of diesel, they exclusively powered naval supply ships and auxiliaries. For instance, every one of the 2,710 Liberty ships fabricated by American shipyards for WWII was powered by triple expansion machinery shafted to single screw.
For the ships' companies, more revolutionary still was the shift away from coal to oil fuel in the 1920s, once again improving their quality of life. It relieved a fortnightly torment known as coaling ship (at left: coaling the pre-dreadnought battleship USS Louisiana, circa 1908). In this periodic agony, the ships tied up next to coal barges, colliers, or other coaling facilities and the men stripped half-naked loaded coal into baskets or burlap sacks and manually brought it aboard. Moved across the decks by wheelbarrow or handtruck, the lumps of fuel were dumped it down hatches and chutes to the bunkers. There trimmers loaded it into wheelbarrows and distributed it around the vessel to balance her trim as refueling proceeded. At the conclusion of each refueling, coal dust would have coated every corner and crack of the vessel. Days of intensive cleaning were required to restore naval spit and polish.
For the coal-burning navies of the world, the management of the fuel below decks and the generating of steam would now revert to the "Black Gang," the coal-dust streaked stokers and trimmers who would manage the coal's storage, deliver it from bunker to stokehold and, with well-aimed shovel strokes, spread the fuel over the glowing aggregate in the ship's furnaces. In the lofty firerooms the great boilers loomed over infernally lit rows of furnace doors, an effect completely lost in early flash photos but nicely captured in this magazine illustration. Nor should we neglect mention of the water tenders, who kept an eagle eye on the water gauges of each boiler, feeding in just enough specially processed feedwater to optimize the production of steam while keeping the boiler temperature from reaching dangerous heights. Visit BBB's Boiler Room for a rundown of the commonest types of marine boilers from the ironclad and pre-dreadnought eras. The marine steam plant was a cooperative effort, an industrial operation of some complexity; but one that in the end rested on the brawn and brains of the firemen themselves.
Little honored in histories of the time, the stokers were the modern equivalent of the rowing slaves who powered the Roman galley, made an indispensable part of modern steam navies until after WWI. They led a life of unremitting, brutal, dirty labor, shoveling the coal into the fire, periodically tending the fires in each of a number of furnaces to ensure efficient combustion, and (worst of all) breaking up the clinker with "slice bars" (small steel girders). Clinker was a red-hot, stone-hard residue of impurities left over when the combustible parts of the coal had burnt off. After the clinker was broken into workable pieces, the stoker had to rake it out of the furnace, extinguish combustion with firehoses, shovel out the ashes, load and despatch the mixture over the side in bucket hoists provided for the purpose. Later ships were equipped with automatic ash ejectors that mixed the debris into a slurry with sea-water and then spat out the mixture through special ports in the side above the waterline; the detritus still had to be shoveled out of the furnace, hand-carried, and loaded into the ejector, however. Then (in addition to tending all his other fires) the stoker had to reignite the newly-cleaned furnace with a fresh load of fuel. A typical boiler might have three or more furnaces, all in the care of a single stoker during his watch. Stoking during rough weather required special moves; experienced firemen knew how to toss in their shovelful on the downward pitch of the ship, avoiding a nasty shower of hot coals around their feet when they opened the furnace door. Despite such technique, fireroom injuries were common.
Depending on the need for steam, the stokers were cued by annunciator bells set in the engine room; they were slaves to the signals of Kilroy's Patent Stoking Indicator as surely as the galley slaves had been to the timekeeper's drum. It was hellish, back-breaking work and the stokers, shunned by 'society' on shipboard and ashore, formed their own hard-bitten in-group. With the impressive physiques built up by their profession, they were renowned pugilists. A number became boxing champions in the Royal Navy and the Russian and Austrian fleets, known for their earthy approach. But their pugilistic forays were not limited to the ring. According to John Maxtone-Graham, "drunken stokers, sometimes wheeled in barrows back on board ship, used to embark upon fearful battles, going after each other with slice bars, tongs, shovels, anything that came to hand. Mates had a standing order when the black gang fought: Close the hatches and stay clear." Maxtone-Graham is writing of the merchant marine, and one presumes that military discipline had a dampening effect on such excesses; but this passage does suggest both the type of man attracted by the profession, and the peculiar dependence of the rest of shipboard society on this nasty, brutish subculture. The same author relates an incident aboard the Cunarder Ultonia in which the stokers broke into the wine stores and defiantly laid down their shovels one day out from their destination. The stokers enjoyed a prolonged bender in lockdown while the best efforts of volunteer deckhands at the shovels produced steam for a pathetic 2 knots. To a man, the Black Gang deserted in New York, leaving the officers to recruit an entire new crew for the return voyage to Europe. [Both: The Only Way to Cross (New York: Collier, 1972), 149.]
Yet without the strong backs and burly muscles of the stokers, none of the fleets of the day could have sailed. And in the hour of need, their efforts were apparent even above decks. At the Battle of Santiago, the flagship USS Brooklyn was described bounding through the billows at unprecedented speed, throwing up a triple bow wave and shooting jets of flame from her stacks. Nor is this the only example of the Black Gang making a signal contribution to military victory.
There is noted in the specifications for many of the later pre-dreadnought ships a small allowance of oil fuel. Starting around 1902, oil was used to assist the speedy raising of steam. To accomplish this, oil droplets were sprayed over the top of freshly heaped coal to assist in speedy combustion, much as we use lighter fuel to fire up charcoal today. This technique was only used when restarting a grate newly raked out and refueled, or in meeting emergency demand for full steam. However, so successful was the technique that it soon led to the replacement of coal by oil fuel -- as had been advocated by that naval visionary, Adm. "Jacky" fisher, as early as 1885. The spray nozzle was refined to an adjustable jet which could efficiently burn oil alone, making all the steam one could wish without the eternal mess and hard labor required by coal. Britain pioneered oil-burning battleships with the Queen Elizabeth class, an innovation championed by both Fisher and Churchill. These huge super-dreadnoughts, armed with 15-inch guns, joined the fleet in 1915. One sympathizes with the Admiralty in their desire to switch. Refueling the British fleet during WWI was a huge logistical headache. It demanded thousands of trainloads of coal be sent weekly to northernmost Scotland. From there it was transshipped to the Orkneys by barge and collier, where it once again it had to be laboriously bagged, shoveled, and lifted by cargo booms and cranes into the vessels of the Grand Fleet in its anchorage at Scapa Flow. During the lengthy spells of enforced inactivity at the base, coaling fleet perversely became one of the breaks in the monotony. Coal mining was a major sector of the economy in Britain and other industrial countries of the time. In just one mining area, South Wales -- home of Welsh steam coal, or anthracite --, there were 250,000 miners who produced 57 million tons of coal in 1913. The peak production of the war years led Britain closer to the depletion of her coal reserves. This -- and labor unrest in the pits -- made the conversion to oil all the more attractive in postwar Britain. Of course, the procurement of petroleum led her into an imperial entanglement in Iran whose repercussions are still being felt a century later.
Pressure gauges on engine of USS Olympia, built 1890-92 at Union Iron Works, San Francisco.