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driving the direct current generator, thus taking advantage of the low steam consumption of the main unit for auxiliary power. At the same time, should the main turbines be down for any cause, this set will con- tinue in operation, driven by its own turbine. There is also a_ turbine driven, direct current generator of 150-kilowatt capacity for emergency use. Each of the main generating units exhaust to a 3500-square foot Worth- ington condenser with motor driven circulating and condensate pumps and air ejectors by the same manufactur-~ er. A matter of interest is the wide use made of centrifugal pumps on this vessel. These pumps were fur- nished by the Dean-Hill Pump Co. and may be enumerated as follows: One six-stage centrifugal, 60-horsepower, motor driven feed pump; one 30- horsepower, motor. driven centrifugal fire pump; one cooler and one sanitary centrifugal pump each motor driven of 15-horsepower; one 74-horsepower motor driven fresh water pump; and one 3-horsepower motor driven drink- ing water pump. So much for the electric motor driven pumps. There is also a 12-inch centrifugal ballast pump by the same manufacturer but direct driven by an Engberg vertical steam engine. Also, one auxiliary feed pump, horizontal duplex, 8 x 12 x 14 inches; and one horizontal duplex bilge pump, 8 x 10 x 12 inches both steam, and supplied by Dean Bros. The feed water heating is done in two stages, using steam extracted from the main turbines. For this pur- pose a low pressure heater of the Griscom-Russel type and a high pres- sure heater of Reilly type are used, the feed water passing through the low pressure first. The final tem- perature of the feed water is 238 de- grees Fahr. Lubricating oil for the main turbine is purified by passing through a De Laval centrifuge. The main generating units are fit- ted with surface air coolers of Gen- eral Electric make. The main motors are cooled by two American Blower Co. fans, each driven by a 25-horse- power alternating current motor. There is one of these fans for each motor and outside air is thus circu- lated through the motor windings. In her steam generating plant the Ciry OF SAGINAW 31 is modern in every respect. Steam is furnished by four Babcock & Wilcox watertube boilers, with interdeck superheaters, at a pressure of 315 pounds per square inch and 200 degrees superheat, and a total temperature of 625 degrees Fahr. Forced draft is used and each boiler is served by one American Blower Co. fan driven by a 7%4-horsepower al- ternating current motor. Draft is maintained at from 1% to 2 inches of air. Each boiler has 5020 square feet of heating surface, 452 square feet of superheating surface, and 120 square ONE OF THE FOUR BABCOCK & WILCOX WATERTUBE, CHAIN GRATE STOKER FED BOILERS ON THE CARFERRY CITY OF SAGINAW 31 30 MARINE REVIEW—December, 1929 feet of grate surface. There is one row of four-inch tubes, other tubes are two inches in diameter. Each boiler is fitted with a Bailey meter. Coal is burned on Babcock & Wilcox chain grate stokers each driven by a 1% horsepower direct current motor. Draft can be regulated in five com- partments by means of dampers, thus insuring proper draft for different depths of fire. The coal burning arrangement on this vessel is of especial interest. The main coal bunker is located athwart- ships, forward of the boilers. Coal feeds from the main bunker on to a pan conveyor, designed and supplied by the Stephens Adamson Co. One of these conveyors operates on each side of the ship, elevates the coal and discharges it, through a crusher if desired, onto a gravity discharge type of conveyor which again elevates the coal and distributes it to fill the small bunkers on either side of the boiler room. These side bunkers contain enough coal for an ordinary run of the carferry so that the conveying sys- tem need only be operated while the vessel is in port. The coal from the side bunkers is fed to the hoppers of the stokers by means of a screw con- ONE OF THE TURBINE CONTROL UNITS veyor. The ash falls off the end of the chain grate into a combined crusher and conveyor, made by the Allen, Sherman, Hoff Co. From this point the ash is conveyed to a sump tank where it is mixed with water and pumped overboard. One of the dangers encountered in the operation of carferries in the winter time is the shock given the machinery when the propellers strike (Continued on Page 64)