ELECTRIC AUXILIARIES ON MERCHANT SHIPS. 163 



cessively large. With the changes in the atmosphere tliat take place below the water line, 

 enclosed motors would be more liable to sweat and accumulate moisture internally than if 

 well ventilated. In general, enclosed self-ventilated motors are recommended for the reason 

 that they are often located in congested places where, if open, they would be liable to me- 

 clianical injury and in addition would have to be protected from dripping water. How- 

 ever, as electrical machinery, when open, is more readily inspected and kept clean, it is not 

 essential tliat tlie motors be enclosed if located, e. g., on a gallery and properly protected from 

 dripping water. Such motors should be screened to prevent rats eating the insulation. On 

 tankers, if the cargo pump motors are of the direct-current type and are located in a special 

 pump room, they must be provided with some means of ventilation which will insure all 

 explosive gases being driven off before the motors are started. 



The motors in the engine room should be insulated with the same care and the castings 

 as thoroughly cleaned and painted as the motors on deck. The insulation on all marine elec- 

 trical apparatus should be made as highly moisture-resisting as possible. 



As illustrating the adaptability of electrical apparatus, the writer recently saw a report 

 from a chief engineer which stated that when the steam engines on his circulating pimip 

 and dry vacuum pump broke down he replaced them by two deck winch motors. The drive 

 was so satisfactory that he intended to recommend that it be made permanent, and inci- 

 dentally the ship burned 1}^ tons of fuel oil per day less after the change. 



Control. — It would seem desirable that the means for starting and stopping each motor 

 be located directly adjacent to it. Such starters are relatively inexpensive. They should be 

 very substantial and moisture-resisting. Thin sheet iron should not be used, especially on 

 any part of the construction which cannot be readily painted, as after a short time it is liable 

 to rust and may be the cause of serious trouble. 



On steam ships the motors on the circulating pump, lubricating oil pump, boiler feed 

 pump, hot well pump, balancer set or lighting motor-generator set, if any, and steering gear, 

 should be fitted with starters, so that when power is restored after an interruption these 

 particular motors will immediately start up automatically. The other motors can be re- 

 started by the engineer at his convenience. 



Generating Units. — A study of the installations on a niunber of cargo ships of various 

 tonnages indicates that on a steamship ISO kw. would give ample power for the deck 

 machinery when in port and for the entire engine-room equipment when at sea. On a motor 

 ship about 75 kw. are necessary at sea. Therefore, on cargo ships of about 10,000 dead- 

 weight tons, two 150 kw. steam turbines or on the motor ships three 75 kw. generator sets 

 would give ample power with one unit for a standby at all times. The auxiliary power in 

 many cases will be much greater than 150 kw. on refrigerator ships and on ships fitted 

 in part for passenger service. The larger the amount of auxiliary power the greater the 

 reason for highly efficient auxiliary turbines. Some studies have shown requirements for 

 auxiliary power as great as 1 ,500 kw. 



Small steam turbines should be rugged and simple, as they will be classed as part of 

 the propelling machinery and therefore vital to the safety of a ship. In sizes of 150 kw. 

 and even smaller, gear reduction would be recommended, as the best direct-current genera- 

 tor operation cannot be expected at the speed at which the turbine should run in order to 

 get good economy. It is expected that these sets will be more substantial and rugged 

 than sets of similar capacity for land service, where they are at all times readily accessible. 



For the reason that on shipboard there is always possibility of scale or salt passing to 

 the turbine from the boilers, it is preferable for the governor to control the speed by means 



