Modern Gasworks Practice

ELECTRICAL PLANT IN GASWORKS CO great use for such machines as elevators and conveyors. They are also most suitable for machines in which there are large momentary overloads, such as coal breakers and pushers. The compound-wound motor, whilst combining the commendable features o£ the shunt and series type, largely eliminates their defects, and is always to be recommended for general gasworks purposes. In order to effect economy in replacements it is preferable to keep to one type of motor and, if possible, to one make. It is not advisable to put down a larger motor than recommended by the makers, for loss in efficiency results and the average machine from a recognized maker will stand a temporary overload without ill effect. ENCLOSED MOTORS The size of motor is largely dependent upon the temperature rise to which it may attain, and in order to use a small motor for a given output good ventilation is essential. It is, therefore, obvious that a totally enclosed motor will have to be very much larger than a semi-enclosed motor of the same horse-power. Owing,, however, to the dusty situation in which many gasworks motors are fixed it is frequently necessary to instal totally enclosed motors. Semi-enclosed motors can be used for driving pumps, fans, and plant generally where the situation is reasonably clean. Totally enclosed motors should in all cases be used for coal breakers, elevators, conveyors, and charging machinery. Special arrangements can some-times be made to use pipe-ventilated motors, which combine the advantages of the totally enclosed and protected types of machines. Pipe-ventilated motors are machines which are totally enclosed but provided with openings to which short lengths of piping, 4 or 5 inch.es in diameter, can be connected. This piping is then taken to clean air and by means of a fan on the armature itself a certain aniount of air is drawn into the motor for cooling purposes. SWITCHES AND ACCESSORIES The switchboard fulfils a function of extreme importance, consequently every care should be taken to ensure that each detail is capable of the work demanded of it. The switches should be up to füll capacity, and the workmanship should be of the best, down to the smallest details of bars, studs, etc. The board may either be built into the wall so as to give outside access, or may be placed well away from it so as to provide ampie space for repairs. The fittings on the board will vary with the requirements and with the different arrangement of the power units. Generally speaking, each generating set is provided with a separate panel fitted with a voltmeter and ammeter, a circuit breaker and a field-regulating switch, together with a main switch and fuse and an equalizing switch. In addition to the generating panels one or more feeder panels are usually installed according to the size of the plant. These feeder panels protect the different circuits running to the works, and are provided with main double-pole switches and fuses enabling any feeder to be isolated. In addition, earth lamps to enable faults on the system