The following details relate to the installation at the Linwood Paper Mills:—
The installation consists of 250-K.W. steam dynamos. The engines are Willan's high speed triple expansion, working with a boiler pressure of 250 lbs. per square inch at the stop valve, the steam being superheated to give a temperature of 500° Fahr. at the engine. By means of jet condensers a vacuum of 25 to 25½ inches is obtained on the engines. The two boilers are of the Babcock type, and have 3,580 square feet of heating surface each. The furnaces have chain grate stokers, and the boilers are arranged with their own superheaters. The motor equipment consists of eight 80, two 50, and ten 25 B.H.P. motors.
Six of the 80 B.H.P. drive the beating engines, and it has been found that the motors readily respond to an overload of 50 per cent. without beating or other trouble. To remedy the excessive and sudden variation a belt drive was adopted. An 80 motor drives the pulp refining engine. The two paper-making machines have each two motors, one a 25 and a 50 and the other two 25 B.H.P. motors. The speed can be regulated with exactitude. The auxiliary plant of the paper-making machine, pumps, agitators, etc., is worked from lines of shafting driven by motors.
Calender motors are of the variable speed type, being designed to run from 100 revolutions per minute to 600 revolutions per minute. Variations from 300 to 600 revolutions per minute can be regulated by the shunts, the loss being negligible. Several of the motors are geared up to the various machines, as is the case with the calender.
As regards cost, the capital outlay on the 500-K.W. generating plant, including engines, dynamos, boilers, condensers, steam pipes, filters, etc., and all engine room accessories, was £9,500.
Fig. 57.—An Electrically Driven Paper Machine.
In addition to the above, the plant also contains a Parson's steam turbine of 1,000 K.W., driving two continuous current dynamos.