892 THE COLLIERY GUARDIAN. APRIL 24, 1914. the basement and directly under the engine, so as to keep the connecting pipes as short as possible and minimise the loss of vacuum. The Balcke condensing plant consists of four surface condensers, with superficial areas of 3,300, 4,000, 6,700 and 7,000 square feet respec- tively, for condensing 16,500, 19,500, 35,300 and 37,400 pounds of steam per hour. The brass condenser tubes are 1 in. in outside diameter, and fitted with self- tightening rubber rings. The plant is designed to furnish a vacuum of about 921 per cent., with the cooling water at a temperature of 27 degs. Cent. (80| degs. Fahr.). Each condenser (fig. 6) has a separate set of pumps, com- prising a centrifugal pump for the condensed water, and an air circulation pump (Westinghouse-Leblanc patent) driven by separate turbines and set up at the head end of the condenser. These turbines are usually non- condensing, and discharge their exhaust steam into the heat accumulator ; but they can also be connected to the condensing plant. The Siemens-Schuckert switchboard plant is set up half-way along one side of the hall, and is divided up, in accordance with the newest system, so that only the appliances required for the main conductors are inside the room itself, whilst the high-tension collecting bars and the high-tension appliances, such as switches, trans- formers, excess tension cut-outs, &c , are housed in the basement. On the platform in front are seven switch- desks (three being at present unoccupied), these being preferred to switchboards, because they facilitate observation of the generators by the switchboard operator. Behind these is a switchwall of 14 panels, for the distribution of the 5,000-volt current supplied to the large motors for driving the fans, pumps, &c., and also the substations at the washery, brickworks, &c. From here also issue the branch conductors to the transformers in the basement, where the current is stepped down to 500 volts for the medium-size motors and to 220 volts for lighting. The secondary conductors of these transformers lead to a second switchwall in the rear of the first, and also divided into 14 panels, where the current is distributed to the 500-volt motors and the lighting circuit. The turbo-generators (fig. 7) are set up immediately in front of the switchboard plant, the turbo-compressors being arranged on the one side, whilst the space on the other side is reserved for extensions. The turbines are supplied with superheated steam at 12-atmosphere pressure and 300 degs. Cent., whilst the high and low pressure turbines are driven by exhaust steam at 1-atmosphere pressure. The turbines for the generators and compressors are all of one type. The cast iron casings are divided horizontally, and the upper halves can be lifted off for inspecting the rotors without dis- turbing any of the conductors. The under halves, on to which the bearings are cast, are mounted on the frames by means of strong feet. The common base plates for turbinesand machines are very strong, and are placed on the foundations without any tie bolts. Each turbine consists of a high-pressure member (velocity rotor) and a low-pressure member working on the reaction principle, and the axial thrust set up in the low-pressure member is taken up by a balance piston. All the bearings are supplied with oil, under pressure, from a pump. For starting, a centrifugal pump is provided on the base plate, and is driven by a small steam turbine mounted on the same shaft. The collar-thrust bearing, mounted in the front bearing pedestal, serves for adjusting the rotor axially and to take up any residual axial thrust. All the governing mechanism is also mounted on the same pedestal, whilst the rear pedestal supports a bearing for the driven machine and the movable coupling between the latter and the turbine. The steam escaping from the stuffing boxes is removed through* special flues. The oil draining from the bearings and valve gear collects in the base-plate, and is run off to a cooler, which in some of the machines is built into the baseplate, but in one case forms an independent unit. Figs. 7 and 8 are sections showing the construction of the two turbines, the only difference between them being that in the one the low-pressure member is of the drum type, whilst in the other the rotor consists—as in the high-pressure member—of separate discs mounted on a powerful shaft. The passage for conveying the steam from the high-pressure side to the low-pressure side can be seen on the underside of the casing. The two Brown-Boveri turbo-generators run at a speed of 3,000 revolutions per minute, which, in view of the high centrifugal force of the rotary members and the requisite cooling of the machines, has necessitated certain constructional modifications in comparison with the standard alternating-current generators. The stator consists of a grey cast-iron casing, in which the stator plates are secured by wedges and lateral compression plates. The bobbin windings are laid in stamped grooves, which are partially closed in the low tension part, and quite open in the high tension part. To increase the strength, and prevent damage in the event of short circuiting, special holders are provided, these being screwed into the lateral plates. Inside the stator the copper is enclosed in a mica tube, the intermediate space between the copper and the tube being filled with lacquer invacuo. On the outside the copper is chiefly insulating with a wrapping of micasolium. The rotor is made of pressed steel in one piece, and is unprovided with any decided poles. The winding is laid in milled grooves, and inside the iron is secured by wedges of drawn brass or steel. Outside very strong caps are provided, to stand the high centrifugal force. At each end of the rotor is a fan for cooling the stator winding. The stator is completely enclosed at both sides by special covers, provided below with an opening for the admission of fresh air into the machine. Part of this ah- is directed against the stator winding by the afore- said fans, the rest passing through special passages in the rotor so as to cool the winding there. Both air currents then flow over the stator plates, which they cool thoroughly, and finally escape through an opening in the casing. Air-Compressing Plants. The two turbo-compressors are of different types. The one first set up is of the two-cylinder type, each 5 T Fig. 4.—General Lay-out of Surface Plant. 1. Shaft I. 2. Shaft II. 3. Compressed air piping. 4. Winding engine. 5. Space for second engine. 6. Store. 7. Winding engine. 8. Do. 9. Steam store. 10. Do. 11. Steam piping to winding engine. 12. Steam piping to turbine plant. 13. Boiler plant. 14. Piping to condensers. 15. Piping for saturated steam to turbine. 16. Piping for water. 17. Turbo-compressor. 18. Do. Do. 19. Do. generator. 20. Do. Do. 21. Switchboard 22. Fresh steam piping. 23. Saturated steam piping. ■ 9HB ill Fig. 5.—General View of Power Station. "V-—— , nt,', ,'f'. Fig. 6.—Condenser Pump and Turbine. a. Turbine, b. Circulating pump for cooling water, c. Westinghouse-Leblanc air pump. d. Pump for condensed water. cylinder containing a number of relatively small rotors. Experience having demonstrated the possibility of increasing the diameter of the rotors, and thus reducing their number and the length of the machine, the whole of the parts in the second (new) compressor have been enclosed in a single casing (fig. 9). The admission of air in both compressors corresponds to the water admission in multiple-stage centrifugal pumps; and, in fact, the entire construction of the compressor cylinder resembles that of such pumps in many respects. The cylinders are built up of sectional rings, and the upper part can be taken off without disturbing the pipes- The bearing blocks are cast on to the suction and pressure heads, and all parts of the cylinder which come in contact with air are carefully water-cooled. The cooling water outlet of each ring is accessible and