The USS Intrepid (CV-11) - Machinery
Machinery : The Essex class were the 1st US carriers to adopt a unit machinery arrangement, the machinery being split into two independent groups, fore and aft. Each consisted of two boiler rooms, containing two boilers each, and an engine room containing two sets of turbines. One pair of boilers supplied steam for one turbine set but a cross connection in the engine room allowed tor alternative arrangements in case of damage or operating convenience. The turbines in the fwd engine room drove the wing shafts and those in the aft engine rooms the inner shafts. Fwd and aft of these compartments were large auxiliary machinery rooms which, together with the auxiliaries in the main machinery compartments contained virtually all the ship's auxiliary equipment apart from the large equipments required for operating the aircraft elevators and catapults. The entire system proved very efficient, both in terms of fuel consumption and maintenance, largely a result of the US development of high power lightweight machinery over a number of years - a process not without cost as initially it meant accepting less than reliable power plants in order to solve the problems involved by practical experimentation. The details of the principal machinery fitted were as follows:
Boilers : The Babcock and Wilcox boilers supplied steam at a working pressure of 65 psi and a temperature of 850 degrees F. Bothe figures were substantially higher than in earlier machinery installations providing a higher power/weight ratio, and giving savings in weight and fuel consumption. It also allowed for a reduction in the size of the boiler uptakes, which helped to minimise the size of the openings in the protective decks, limited the encroachment of the funnels on hangar space and improved on the space available in the island superstructure.
The boilers operated under forced draught, each having two blowers (fans) which fed pressurized air directly into the boiler casing (obviating the need for a closed stokehold) and thence to the air intakes around the oil fuel sprayers. The boiler had a split furnace - a standard saturated steam furnace on the right heating the main generator tubes connecting the water drum at bottom right to the drum at top center, and a superheat furnace on the left to boost the steam in the superheater, at the boiler's center rear, before its heat passed across to the saturated side to assist in heating the generator tubes prior to passing into the uptake. Further heat saving was achieved by an economiser fitted in the uptake, through which the boiler feed water was passed to be pre-heated by the waste furnace gases. Each boiler was supplied by a fuel oil service pump, a fuel oil heater, a main feed pump and, in case of breakdown or maintenance, an auxiliary feed pump. In addition there was one port fuel oil service pump, for use in transferring oil when ship power was off, and one fuel oil hand pump, for emergency use, in each boiler room. Separate fuel oil boost and transfer pumps and tank drain pumps were fitted in the after auxiliary machinery room, pump rooms and Nos 1 & 3 boiler rooms for the transfer, of oil fuel from tank to tank, etc.
Turbines : Each of the 4 sets of Westinghouse turbines consisted of a low pressure (LP) and a high pressure (HP) turbine driving the propeller shaft via a double reduction gearbox. The latter allowed a much greater speed reduction than the single reduction gearbox and again provided high economy as the turbines, running at a higher speed, were more efficient in their use of steam. The turbines were also of less weight but this was offset by the greater weight of the gearing. Astern turbines were fitted at the ends of the LP turbine (in the same casing) and a cruising turbine, for economy at low power, was geared to the forward end of the HP turbine. When cruising steam was fed to the cruising turbine, then exhausted into the HP turbine which in turn exhausted into the LP turbine. At higher powers the steam was fed directly into the HP turbines. Each turbine set had a main condenser (slung inder the LP turbine from whence it drew the exhausted steam), 1 motor-and 1 turbo-driven forced lubrication pump, a gland vapor exhauster and condenser; and for the condenser, a main circulating pump, 1 motor-and 1 turbo-driven condensate pump and a main air ejector. In addition each engine room had a lubricating oil purifier (or filter), a de-aerating tank for the feed water and four feed boost pumpsto transfer feed water back to the boilers.
Electrical Plant : 4 1250kW turbo-generators, located in the fwd action machinery room, # 1 engine room and # 3 and 4 boiler rooms supplied the ship's main power requirements. Each generator had its own set of turbine auxiliaries, including a condenser, circulation pump, lubricating oil pump, etc., as with the main turbines. In case of heavy loss of steam power 2 250kW diesel generators were also provided,1ineach auxiliary machinery room, each having a diesel fuel service pump, a cooling water pump and a fuel purifier. Ship's service motor generators, 1 in the fwd auxiliary machinery room and 1 in # 4 boiler room supplied the majority of the ship's low power requirements. There were also 3 emergency 60kW generators on the main deck.
Distillation Plant : This provided fresh water, for boiler feed and ship services (washing and drinking water, etc.), by boiling sea water and condensing the vapor. For economy of power the vapor generated from 1 evaporator was usually used to heat another evaporator before being condensed. The Essex class had 3 such plants, 1 small 2-stage (or double effect) evaporator and its auxiliaries being fitted in # 3 boiler room, and 2 very large 3-stage evaporator sets in the fwd auxiliary machinery room. In each compartment 2 fresh water pumps were provided to transfer the distilled water to the ship's services and/or the feed tanks.
Air Compressors : High pressure and a medium pressure air compressors were fitted in the 2 auxiliary machinery rooms and a high pressure and a low pressure air compressors in # 3 boiler room to supply air for armament, a/c and sundry other purposes.
Degaussing System : As defense against magnetic mines the Intrepid carried an internal degaussing coil supplied by 4 motor generators, 2 in # 3 boiler room and 2 in the forward machinery room.
Fire Pumps : For fire-fighting and wash deck purposes and for pumping out flooded compartments, 9 fire pumps were fitted, 1 in each main machinery room, 1 in the aft auxiliary machinery room and 2 in the pump rooms fwd.
Bilge Pumps : 1 bilge pump was fitted in each main machinery room for clearing the bilges and for pumping out the machinery compartments in case of flooding.
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