The Liberty Ship Engine
he engine of the JOHN W. BROWN, like that found on all Liberty ships, is a unique and fascinating relic of an earlier day in marine propulsion.
Since the inception of Project Liberty Ship's plan to bring the JOHN W. BROWN to Baltimore in 1988, the goal was to create a living, steaming museum and memorial. Static displays have their place, and there are many of them all around the country. Some of the World War II memorial ships, like battleships, for example, are far too complicated and vastly too expensive to be operated by small museums staffed mostly with volunteers. But with a merchant ship, with its relatively simple power plant, reactivation is a distinct possibility. It had, in fact, already been done on the West Coast by the volunteers on the Liberty ship JEREMIAH O'BRIEN.
Since the BROWN arrived in Baltimore her volunteers have amassed 750,000 hours of labor, about half of which has been directed to the reactivation and maintenance of her power plant systems -- boilers, main engine and auxiliaries.
The BROWN is a steamship but a very special steamship, since her main engine is a triple-expansion steam engine, a type that has all but disappeared as a means of propelling ships. Prior to World War II, the expansion steam engine dominated marine applications where high vessel speed was not essential. It was, however, superseded by the steam turbine where speed was required, for instance in warships and ocean liners.
This type of engine was designed around the turn of the 20th century in England. It was already largely obsolete when it was chosen to power the fleet of emergency cargo ships to be build for the U.S. Maritime Commission in 1941: the Liberty ships. The selection of the triple-expansion engine was based on the lack of availability of manufacturing facilities for the modern steam turbine engines. All of the companies capable of producing the reduction gears and turbines for these engines were fully committed to naval and high-speed merchant ship orders. The triple-expansion engine was easier to build and could be manufactured by companies that lacked the precision machine tools necessary to build turbine engines. Another important factor was the ruggedness and simplicity of the engine. Most of the engine room personnel being trained to man the emergency fleet had little or no seagoing experience and would be learning "on the job."
Fully assembled, the engine weighs 270,000 pounds. It stands 19 feet tall and is 21 feet long. The ship's four-bladed propeller, 18 feet in diameter, is directly coupled to the engine, which is designed to turn at a maximum of 76 rpm. This gave Liberty ships a top speed of about 11 knots. Aboard the BROWN the engine is normally run at 65 rpm, which saves fuel and is easier on the engine. This gives an average speed of around 10 knots. Power output from the engine is 2,500 horsepower. Fuel consumption is about 170 barrels (30 tons) of oil per day at 11 knots, giving a range of 19,000 nautical miles.
During World War II, fuel for the engine was so-called bunker C oil, a very heavy, viscous material that had to be heated in the fuel tanks before it was liquified enough to be pumped to the boilers. Today aboard the BROWN we burn diesel oil as our fuel so as to avoid the need to preheat the oil.
The British-designed engine was adapted for American production by the Hooven, Owens & Rentschler Corp., a subsidiary of the General Machinery Company of Cincinnati, Ohio. Engines were eventually built by eighteen different manufacturers all over the United States. The BROWN's engine was built by the Worthington Pump & Machinery Corp. in Harrison, New Jersey. Parts for the engines were entirely interchangeable with those built by any of the eighteen manufacturers. Each engine cost approximately $100,000 to manufacture.
The term "triple expansion" refers to the fact that steam is fed in turn to the three cylinders of the engine, one after the other. The engine is supplied with steam at 220 pounds gauge pressure and 445 degrees F. from two oil-fired water tube boilers. The three cylinders are the high pressure (24 inches diameter), intermediate pressure (37 inches diameter) and low pressure (70 inches diameter) cylinders, and all have a piston stroke of 48 inches. Somewhat simplified, the engine operates in this manner: Steam from the boilers is supplied first to the high pressure cylinder via its valves, and is then exhausted, at a reduced but still considerable pressure, through the same valves to the intermediate valves and cylinder. From there, the steam passes directly into the low pressure valves and cylinder. The cylinders become progressively larger but even though there is a drop in steam pressure through each successive cylinder, the work done by each cylinder is the same. The steam is exhausted from the low pressure cylinder to a condenser and cooled back to water and reclaimed to feed the boiler, which cannot use seawater.
The unique feature of the triple-expansion engine is its openness. Most of its moving parts are readily accessible and visible to the observer. Piston rods, crankshaft, eccentric rods, crossheads and reversing mechanism for a fascinating symphony of motion. The engine is lubricated entirely by gravity feed and hand-oiling. The watch-standing oiler makes his rounds of the engine room every 20 minutes or so, using his oil can and feeling the moving bearings for excessive heat buildup. His hand darts in and out between piston strokes, a job not for the faint of heart.
On really hot days, the temperature in the firing aisle between the boilers can reach 130 degrees F. The entire engine room is a symphony of motion, since all the auxiliaries are powered by small, single-cylinder reciprocating steam engines. The motion is accompanied by the characteristic aroma of steam, fuel oil and hot lubricating oil that steam engineers love so dearly.
Most of the BROWN's licensed engineers are World War II veterans who hold unlimited licenses as chief engineers of steam vessels, of any horsepower. Many of the oilers and firemen/watertenders are veterans as well. Project Liberty Ship, however, has begun a comprehensive training program to instruct younger volunteers in the art and science of triple-expansion steam engineering. It takes years of experience, skill and knowledge and long hours of hard, dirty work to keep this great engine running.
As long as Project Liberty Ship has engineers to fire the BROWN's boilers and operate her machinery, she will continue her mission as a "living, steaming memorial" to those who built, sailed and defended our wartime merchant marine.
© Project Liberty Ship
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