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_work he has to look after. Oe TP Pa eee ee 34 THE. MARINE. REVIEW ELECTRICITY ON STEAMERS There can be no doubt that electric lighting (for that is the principal use of electricity on merchant and small pas- senger steamers) is a- "reat boon to all on board, and, in the case of passenger boats, can almost be considered. indis- pensable. It is healthy, clean, free from smell or. smoke, is quite independent of any motion of the ship, and above all is adaptable to any out-of-the-way position where light may be necessary. For all concerned I think it should be an invari- able rule that all steamers should carry an electric lighting plant. The power required is small, varying, of course, with the size of the ship. The number of lights required may be from too to 200: for cargo. boats, these numbers representing about 10 to ao 8. HH. FP. for the engine... Tak- ing an installation of 100 lamps, and as- suming that three-fourths of them are _used on the average 12 hours a day for 305 days, the coal required -would be about 75 tons, or, say, about 4% cwt. per day, or 5 lbs. per B. H. P. per hour. Such a small amount would never be felt, and even this estimate will prob- ably be found to be high, depending upon the economical use of the lamps and the careful running of the engine. This will be the chief expense of the lighting, as there will be no charge for attendance, since no additional staff need be carried except in large passenger boats, where - separate plant and staff are carried for electrical work. The other costs include oil for engine and dynamo, replacement of lamps and defective fittings. In describing the installation it will be convenient to take the different sec- tions in the following order: Plant, switchboards, wiring and fittings. All marine engineers should try to gain some slight knowledge of electrical matters. With a good book to read and the ship's installation to follow, an engineer should 'soon gain sufficient information to ap- ply it in a common-sense way to the A dynamo is a simple machine to work; at the same time it will not run without attention, but if properly handled should last for years in good condition. For the com- fort of all on board and the safe working of the ship it is essential that the light- ing should not fail and only a complete shut down can occur if the engine or dynamo breaks down. As a rule boats generally carry one lighting set only, but it is good practice to have two sets, each capable of taking, say, three-quar- ters of the total load. Then if one ma- chine is entirely disabled, it would be an BY H. HENDERSON easy matter to keep the load down to that of one engine by .outting off any unimportant lamps. The type of dynamo ' generally used is of the two or four pole compound wound machine, preferably partially enclosed to protect the wiring in the armature and magnets from stray splashes of oil or water, the greatest ene- mies of electrical work. Carbon brushes are generally used, as they give better re- sults than copper gauze-brushes. The end bearing of the dynamo is fit- ted for ring lubrication, thus taking the minimum of attention and oil. All dyna- mos afe built for direct coupling to the engine. This method has great advan- tages in that the space occupied is a min- imum, and also dispenses with one bear- ing, viz., that between the dynamo and engine. With regard to the position of the plant, the bottom or starting plat- form in front of the main engine is used in cargo boats. This position has the ad- vantage that it is right under the eye of the engineer in charge. If it is a twin- screw boat, the thrust recess forms a very good position. The shaft (unless absolutely impossible) should be placed fore and aft. The armature and shaft are thus not so much affected by the rolling of the ship. Also with the engine aft, the chance of oil and water running on to the armature is very much lessened. SWITCHBOARDS.--The main switchboard is rather an important part of the plant, 'as it forms the connecting-link between the dynamo and the lamps. It is also an indicator by which the engineer can tell whether his pressure of supply (voltage) is correct, and whether the dynamo is being overloaded or not. If only one machine is fixed the arrangements are simple. The apparatus should consist of two main switches and fuses, one for each wire from the dynamo terminals. From the fuses connections should be made to two bars commonly called bus- bars. To one of these bars are con- nected circuit switches and fuses and to the other circuit fuses only. The rest of the apparatus consists of an ammeter for measuring the main current and a volt- meter to indicate the pressure of supply. The whole of the apparatus should be mounted on an enamelled slate panel, and the board mounted on an iron frame, leaving sufficient space behind to allow for connecting up the different' wires. If two dynamos are used, the board becomes larger, but still quite simple. Each dynamo is connected up independ- ently, so that each can take all the load singly, or the load may be divided be- tween them. Owing to a certain pecu- liarity of compound wound dynamos it requires care to run them coupled to- gether electrically, as would be the best method to do. Therefore, it is safest to arrange the dynamos so that each is in- dependent of the other. ° The board car- ries three bus-bars instead of two, and in place of a simple circuit switch, a change-over switch is used so that any cifcuit can be thrown on to either ma- chine. Of course, it is necessary to have two sets of main cut-off switches and fuses and also two ammeters, one for each dynamo. One voltmeter only is necessary and should be fitted with a switch so that each machine can be tried in turn. If the current falls so that one dynamo could run all the lights in use, then all the switches can be put over the dynamo to be left running and the other shut down. Wirinc.--When electric lighting was first adopted for ship work one of the most controversial points was the sys- tem of wiring to be used. There are three systems in use: Double wiring throughout, both lead and return being insulated; double wire throughout, the lead being insulated, and the return act- ing as a protective covering, and not in- sulated; single wiring, the lead being in- sulated, and the ship's ironwork acting as 2 return. The first system is that in use on land, and is certainly the best for ship work. The wire generally used is twin wire with wire armouring over the insulation, and in some cases protected with lead covering. Wires leave the circuit ter- minals at the main switchboard and run to different sections of the ship. These form main distributing wires' which ter- minate in fuse boxes in which are placed branch fuses for the protection of each branch leading to lamps. This box forms a convenient method of connecting up the separate circuits with the main circuit, From the fuse-board run smaller wires to the center (or as near as possible to it) of each group of lamps. These wires are terminated in an extension box, and from this radiate to the different lamps and switches. Thus no jointing is done, which is a great advantage. If any sec- tion of wire goes wrong it is easily re- placed at a minimum of trouble, re- quiring no skill, but only a little care to notice where the proper ends of wire are to be placed. The second system of wiring is very safe, but is troublesome to install and repair. Special fittings are required where aty connections are to be made to lamps, switches, etc., as the outer con- ductor or armouring must necessarily be cut to get at the inner conductor, and