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Iowa-class battleship
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=== Propulsion === {{multiple image | direction= vertical | align = right | width = 220 | footer = | image1 = USS New Jersey engine room controls.jpg | alt1 = A large panel with many dials. A man works a wheel at the far right end of the image. | caption1= A crewman operates the ship's throttle in the main engine room aboard ''New Jersey'' (1982) | image2 = USS New Jersey electrical generators.jpg | alt2 = A large room with gray machinery visible on the right and gray and orange machinery visible on the left. Three men in light blue shirts and one man in a black shirt are working on the equipment. | caption2= Crewmen operate the electrical generators in the upper-level engine room aboard ''New Jersey'' (1982) }} The powerplant of the ''Iowa''s consists of eight [[Babcock & Wilcox]] boilers and four sets of double reduction cross-compound geared [[steam turbine|turbines]], with each turbine set driving a single shaft. Specifically, the geared turbines on ''Iowa'' and ''Missouri'' were provided by [[General Electric]], while the equivalent machinery on ''New Jersey'' and ''Wisconsin'' was provided by [[Westinghouse Electric Corporation|Westinghouse]].<ref name="IOWA MACHINERY">Preston, p. 259.</ref>{{sfn|Sumrall|1988|pp=135β137}} The plant produced {{cvt|212000|shp}} and propelled the ship up to a maximum speed of {{cvt|32.5|kn}} at full load displacement and {{cvt|33|kn}} at normal displacement.{{refn|The empirical formula permitted a theoretical maximum speed of {{cvt|34.9|kn|1}}. However, the actual maximum speed of the ''Iowa''-class battleships was never verified during World War II as the ships never ran a measured mile at full power; {{cvt|31|kn|1}} was considered the operating speed when bottom fouling and sea state were taken into account.{{sfn|Friedman|1986|p=317}} During 1985 sea trials, ''Iowa'' achieved {{cvt|31.0|kn}} at {{cvt|186260|shp}} and nearly full load displacement of {{cvt|55960|LT}}.<ref>{{cite web |last= Toby |first= A. Steven |date= 23 June 2011 |title= Speed Thrills V |website= NavWeaps.com |url= http://www.navweaps.com/index_tech/tech-104.php |access-date= 20 November 2020}}</ref><ref>{{cite report |last= Stenson |first= Richard J. |date= October 1989 |title= First of Class Trials on USS Iowa (BB-61) Class β Past and Present |url= http://www.navweaps.com/index_tech/tech-104_BB61_Sea_Trial.pdf |publisher= [[Carderock Division of the Naval Surface Warfare Center|David Taylor Research Center]], U.S. Navy |location= Bethesda, Maryland |access-date= 20 November 2020 |via= NavWeaps.com}}</ref> When lightly loaded, ''New Jersey'' achieved {{cvt|35.2|kn}} in shallow waters during machinery trials in 1968.<ref>{{cite web |last= DiGiulian |first= Tony |date= 8 November 1999 |title= Speed Thrills II: Max Speed of the Iowa Class Battleships) |website= NavWeaps.com |url= http://www.navweaps.com/index_tech/tech-029.htm |access-date= 20 November 2020}}</ref>|group=N|name=Speed}} The ships carried {{cvt|8841|LT}} of fuel oil which gave a range of {{cvt|15900|nmi}} at {{cvt|17|kn}}. Two semi-balanced rudders gave the ships a tactical turning diameter of {{convert|814|yard|0}} at {{cvt|30|kn}} and {{convert|760|yard|0}} at {{cvt|20|kn}}.{{sfn|Friedman|1986|p=449}} The machinery spaces were longitudinally divided into eight compartments with alternating fire and engine rooms to ensure adequate isolation of machinery components. Four [[fire room]]s each contained two M-Type [[boiler]]s operating at {{convert|600|psi|kPa kg/cm2|0|lk=on}} with a maximum superheater outlet temperature of {{cvt|850|Β°F}}.{{sfn|Sumrall|1988|pp=135β137}}<ref>Stillwell, p. 22.{{Incomplete short citation|date=November 2020}}<!--Ambiguous, there are two Stillwells (1986, 1996) cited in article--></ref> The double-expansion engines consist of a high-pressure (HP) turbine and a low-pressure (LP) turbine. The steam is first passed through the HP turbine which turns at up to 2,100 rpm. The steam, largely depleted at this point, is then passed through a large conduit to the LP turbine. By the time it reaches the LP turbine, it has no more than {{cvt|50|psi|kPa}} of pressure left. The LP turbine increases efficiency and power by extracting the last little bit of energy from the steam. After leaving the LP turbine, the exhaust steam passes into a condenser and is then returned as feed water to the boilers. Water lost in the process is replaced by three evaporators, which can make a total of 60,000 US gallons per day (3 liters per second) of fresh water. After the boilers have had their fill, the remaining fresh water is fed to the ship's potable water systems for drinking, showers, hand washing, cooking, etc. All of the urinals and all but one of the toilets on the ''Iowa'' class flush with salt water in order to conserve fresh water. The turbines, especially the HP turbine, can turn at 2,000 rpm; their shafts drive through reduction gearing that turns the propeller shafts at speeds up to 225 rpm, depending upon the desired speed of the ship.{{sfn|Sumrall|1988|pp=118β119}} The ''Iowa''s were outfitted with four screws: the outboard pair consisting of four-bladed propellers {{cvt|18.25|ft}} in diameter and the inboard pair consisting of five-bladed propellers {{cvt|17|ft|2}} in diameter. The propeller designs were adopted after earlier testing had determined that propeller [[cavitation]] caused a drop in efficiency at speeds over {{cvt|30|kn}}. The two inner shafts were housed in skegs to smooth the flow of water to the propellers and improve the structural strength of the stern.{{sfnm|1a1=Sumrall|1y=1988|1p=138|2a1=Rogers|2y=n.d.|2pp=5β6}} Each of the four engine rooms has a pair of 1,250 kW Ship's Service Turbine Generators (SSTGs), providing the ship with a total non-emergency electrical power of 10,000 kW at 450 volts alternating current. Additionally, the vessels have a pair of 250 kW emergency diesel generators.{{sfn|Friedman|1986|p=449}} To allow battle-damaged electrical circuits to be repaired or bypassed, the lower decks of the ship have a Casualty Power System whose large 3-wire cables and wall outlets called "biscuits" can be used to reroute power.{{sfn|Garzke|Dulin|1995|pp=142β143}}
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