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of the oil when the vessel pitches. Generating sets should be mounted with their shafts in a fore and aft position, not only to facilitate pro- vision against oil leakage as a result of tilting the generator, but also to reduce bearing pressures as a result of the gyroscopic action of the rotat- ing parts. The stopping of oil leaks from the bearings of electrical machinery has seemed to Westinghouse of such im- portance that a sealed sleeve bearing has been developed which will operate for a long priod without attention, leakage or replacing the oil. Designed to Suit Service Special considerations in the de- sign of the mechanical parts are de- pendent both upon the location and form of drive of the sets. Often the sets are located where dripping moisture is a source of danger to the commutators and exposed windings. The addition of canopy covers to the tep halves of the frames, is effective in diverting dirt and moisture which otherwise may cause damage. Regarding the question of suitable voltage supply for use on shipboard, the American Institute of Electrical Engineers through the Marine com- mittee, has recommended 240 volts for auxiliary sets except for small capacities where the ratio of power load to lighting load is usually small, in which case 115 volts is recom- mended. ‘The determination of capacities and number of generating sets, is a con- sideration dependent upon the normal and maximum loads at sea and in port. Usually the loads at sea are fairly steady, these being made up of lighting, engine room auxiliaries, steering gear, heating appliances, and the like. The port load for cargo- carrying vessels, excepting those hav- ing liquid cargoes, is generally fluctu- ating, being composed of the winch load, lighting and small power loads. The determination of the size of the plant is often based on the port demand, this being greater usually than that at sea, both because of the comparative size of the winch load, and on account of its fluctua- tions. For obvious reasons, a spare set which can be substituted for any other connected to the auxiliary pow- er bus, should be installed as a part of the regular plant equipment. Need Two Generating Sets In order that the power supply be reliable, especially for sea-going ves- sels and those operating on the Great Lakes, not less than two generating sets should be installed on any one ship. Exceptions to this rule are found on small boats operating on bays, sounds, and lakes other than the Great Lakes, where a single set is augmented by storage battery op- eration, and a comparatively small emergency generator. For river ves- sels, one generating set of peak load capacity is specified by the Marine ELECTRIC DRIVEN AIR COMPRESSOR ON THE TANKER J. W. VAN DYKE 58 MARINE REVIEW—November, 1927 rules as adequate for the service. The extensive use of electricity on diesel ships, especially the larger ones carrying passengers on the ocean, has actually made necessary for some of them. the largest auxiliary power plants afloat. The auxiliary plant on the passenger and _ freight liner MONTE SARMIENTO (gross tonnage 13,628) built in 1924 for the Ham- burg South American Steam Navi- gation Co., has five 450-kilowatt, 220 volt, direct current generators, direct connected to diesel engines. This surpasses the size of the auxiliary power plant on the LEVIATHAN, or even that of a modern battleship, and indicates the growing popularity of electricity on shipboard. Motors and Controllers Usually because of the fact that the location of most of the auxiliary mo- tors is likely to be less favorable than that of the generators, the former are more completely enclosed than the latter. Drip-proof and en- closed, self-ventilated motors are ap- plied most generally in the engine room. However, where the location of the motor is such as to give it good protection from mechanical in- jury and the dripping of water or oil, open motors are permissible. Contactor type starters enclosed in drip-proof ‘cabinets and having the push button type of masters are very popular. Centralized control _ sta- tions, having the switchboard type of controllers, have been applied with much success to engine room equip- ment and blower installations located elsewhere throughout the vessel. Although the centrifugal pump is well suited to direct connection to the motor shaft, and therefore, its wide use on shipboard is highly de- sirable, installations where suction is necessary are more _ satisfactorily made by means of positive displace- ment pumps. Moreover, the piping layout may include air pockets, or the supply tanks, like the bilges, may be below the level of the pump suction. Under such conditions, when the vessel is under way and _ the liquids, having low levels, .are agi- tated and air introduced, satisfac- tory service from centrifugal pumps cannot be obtained. Hence, recourse is made to positive displacement pumps for bilge and ballast service, .and often for the fresh water supply. Motors for driving plunger pumps should preferably be totally enclosed, or at least enclosed on the driving end. ‘The drip-proof motor can be excellently applied to the rotary and centrifugal pump. The coupling form of drive permits the use of normal shaft and bearing sizes, also mini-