THE COLLIERY GUARDIAN. February 26, 1915. 436 __________________________________________________________________________________________________________ surface condenser, which has 12,800 sq.ft, cooling surface, is immediately under and parallel to the turbine. The turbine exhaust and the condenser are connected by a water-sealed gland. The condensing auxiliaries consist of three centrifugal pumps, driven by vertical shafts, the motors (induction slip ring type) being fixed iat the floor level. The circulating water pump is driven by a 140-horse power motor, and the air and water extraction pump by a 75-horse power motor, air being extracted by a jet of high-pressure water forced by the centrifugal pump through the air ejector. The motors are erected at the floor level, so that in the event of the basement being flooded the auxiliaries could still be run, any water entering the basement being dis- charged by the opening of a valve on the circulating pump suction. (b) Use of Exhaust Steam.—Exhaust steam from existing winders and compressors is utilised at the following collieries :— Exhaust steam. ______________________ > ; A Maximum Average per rate of flow hour winding per minute. shift. steam at the rate of 80,0001b. per hour, the surface condensers having a cooling surface of 15,000sq.ft. The condenser auxiliaries consist of an auxiliary steam turbine driving a Leblanc air pump, a centrifugal cooling water pump, and a condensed steam extracting pump, and running at 2,500 revolutions per minute. The auxiliary turbine, which develops 150b.h.p., exhausts into the low-pressure steam system between the accumulator and the main turbine. The following are the consumptions of low-pressure and high-pressure steam per kw.-hour when working under mixed- pressure conditions :— the gas engine plant not exceeding 100 kw’. with the turbine fully loaded. The condensing plant is of the jet type, with a Leblanc air pump and circulating pump driven by a 160-horse power motor at 480 revolutions per minute. The following are the steam consumptions per kw.-hour of this plant when operating under mixed- pressure conditions :— Low-pressure High-pressure steam. steam. i b. Lb. Full load ... 30 ... — Do....... — ... 15’6 Vacuum (bar. = 30 in.). 28’5 28’75 Lb. Lb. Elliot.............. — ... 50,000 Penallta ........... 2,600 ... 60,000 Bargoed____________ 2,000 ... 75,000 Low- High- Vacuum pressure steam. pressure steam. (bar. = 30 in.) Lb. Lb. Full load 20 6’4 27’5 Three qr. load 26’6 3’6 27’65 Half „ 40 — 27’9 The plant has been in operation since 1912. The latest application is at Bargoed, where the exhaust from three main winders, steam compressor, and fan is utilised. Owing to the considerable back pressure on the main winders with the Rateau system (the back pressure varying from 2-J- to lb.) it was decided to adopt the Samuelson system. The steam accumulator is of the gasometer type having a capa- Fig. 3.—Middle Duffryn Power House. J '-x J Mte» i'E Turbine Turbine 4- llllllllllllllll liiiiiiiiiiii Fig. 4.—Bargoed Power House. RtWVE. STEAM JtlTEAKATOH 7M k w. Scale of feet Feet to 5 o io to w aoFeet Fig. 5.—Bargoed Exhaust-Steam Mains and Accumulator. The plant at the Elliot Pit has been in use since 1909; and whilst satisfactory service is obtained during the normal winding hours, the use of this plant is limited to the day shift, as it cannot bo run efficiently on live steam. The second application was at Penallta, where the exhaust steam from the two main winders and a com- pressor is utilised through two Rateau steam accumu- lators in conjunction with two 3,000 kw. Westinghouse mixed-pressure turbo-alternators. The turbines are designed to give an output of 1,800 kw. with 60,0001b. of low-pressure steam, and when working mixed pressure to give an output of 3,000 kw. with 60,0001b. of low- pressure steam and 19,0001b. of high-pressure steam at 1501b. per sq. in., 100 degs. Fahr, superheat. As this plant works in parallel with the gas engine station at Bargoed, close speed regulation was necessary, other- wise the gas engine plant would have been overloaded each time the plant changed from high-pressure to low-pressure steam. The makers were very successful in this application, tests showing that the alteration of frequency when changing from high-pressure to low- pressure steam did not exceed 0’3 of a period. The interchange' of load when the gas engine station is working at an average load of 1,800 kw. and the turbine load is 2,000 kw. does not exceed 500 kw. The con- densing plant for each turbine is designed to deal with city of 12,000 cu. ft., the dimensions being:—Internal diameter, 30 ft.; height closed, 19 ft. 2 in.; height extended, 39 ft. 6 in. The average quantity of steam dealt with is 60,0001b. per hour, the momentary maximum rate of flow being 160,0001b. per hour, any excess steam not used by the turbine passing to the feed water heater. From the working of this plant since October 1914 it has been found that the back pressure on the main winders never exceeds 0’5 lb. Owing to the pressure variation being very small, it is impossible in this instance to control the admission of the low7-pressure steam to the turbine by change of pressure, as in the Rateau system; the supply of exhaust steam is therefore directly controlled from the steam accu- mulator, an oil relay valve being actuated when the former is 2’5 ft. from its lowest position, which valve definitely closes the low-pressure steam valve on the turbine until a further supply of exhaust steam is available. Fig. 5 shows the general arrange- ment of the exhaust steam mains and accumulator. Exhaust steam is supplied to a 2,000kw. 3,000 revolu- tions per minute Fraser and Chalmers—Siemens turbo- alternator. This set supplies current into the common network. The governing is extremely good, and no difficulty has been found in changing from low-pressure to mixed-pressure steam, the interchange of load with The following table shows the progress made in reducing the steam consumption of low-pressure steam turbines during the last six years :— No of sets ............... Output per set (power factor 0’75)______________K.v.a. Speed .............R.p.m. Vacuum (bar. — 30 in.) In. Low-pressure steam consump- tion per kw.-hour at load in following column .....Lb. Load..................Kw. Elliot Penallta Bargoed (1908). (1911). (1914). 2 ... 2 ... 1 625 ... 4,000 ... 2,800 1,500 ... 1,500 ... 3,000 27 ... 27’5 .. 28 5 50 ... 33’7 ... 30’2 500 ... 1,800 ... 2,000 (c) Gas Engine Plant (Bargoed).— Number of working ovens ................. 100..... Type—regenerative Koppers and Simplex Coal—average quantity carbonised per week... 4,700 tons Coke—average output .. __.............. 3,800 ,, The gas engine plant is part of Mr. E. M. Hann’s scheme for dealing with small coal. About half of the total quantity of gas is required for heating the ovens, the balance, which is used for the following require- ments, is delivered to a gasometer holding 300,000 cu. ft. Cu. ft. per week. Average. (1) Gas engines .................. 12,040,000 (2) Sale to uas company ___________ 3,000,000 (3) Firing boilers.................. 3,710,* 00 Analysis of gas— Per cent. Hydrogen ......................... 56’4 Methane.......................... 20’5 Carbon dioxide .................... 18 Heavy hydrocarbons .............. 1’9 Oxygen .....> .................... 0 9 Carbon monoxide .................. 4’7 Nitrogen .......................... 13’8 Thermal value 400/410 B.Th.U.—Lower value. Gas engines of the Nuremberg type, double-acting four-cycle, are direct-coupled to flywheel alternators, one of 1,000 k.v.a., and two of 2,000 k.v.a. rating, running at 3,000 volts and 100 revolutions per minute. The smaller set is of the tandem type and the larger sets twin-tandem, developing at normal full load rating 600 b.h.p. per cylinder. Cylinders 34 in. x 43 in. stroke. Weight of flywheel of 2,400 b.h.p. sets 76 tons. Diameter of shaft of 2,400 b.h.p. sets 30 in. These plants were originally worked at average loads of 700 and 1,400 kw. The combined maximum load for one large and one small set is 2,500kw., the usual practice being to run one large gas .engine continuously and the smaller gas engine during the day shift. When working at these loads, the cost of repairs was found to be unduly high on cylinders, pistons, piston rods, and exhaust valves, and since 1912 the plants have been worked at average loads of 600 and 1,1200kw., the com- bined maximum load being 2,200 kw. Since modifying the rating of this plant, the life of pistons, piston rods, and exhaust valves has increased, and no cylinders have been cracked. Tests showed that the heat consumption of the 2,000k.v.a. sets was:— B.Th U. per kw.-hour. At full load ......................... 12,800 At half load __.................................... 20,400 In order to utilise the surplus gas to the best advan- tage, electric pumping was adopted simultaneously with the erection of the gas engine plant, and by providing high-power pumps and increasing the size of lodge rooms, it was found possible to confine the hours of pumping to from eight to 12 per day at the Elliot Pit. The gas engine plant thus supplies the general colliery demands during the day and the main pumping at night. With an output of 14 million units per annum and a maximum load of 2,200 kw., the annual load factor of the gas engine station is 72 per cent. (d) Fuel.—Until recent years the South Wales coal- field has been at a great disadvantage owing to the unsuitability of the average class of “ dry smalls ” for use on mechanical stokers, the main product of the coal- field being of special value for hand firing for marine and locomotive purposes. With the increasing, import- ance of small coal, much attention has been given to mechanical stokers, and the modified form of furnace introduced by Messrs. Babcock and Wilcox, in conjunc- tion with Mr. E. L. Hann, has solved the problem of burning “ dry small ” coals. No general statement can be given as to the total fuel consumption, as in the case of the Powell Duffryn Com- pany 14 million units are generated by coke oven gas, about 14’5 million by exhaust steam, and the balance of 21’5 million by live steam. In the case of the Abera- man Collieries, the weekly coal consumption, operating on a station load factor of 47 per cent., is 2’9 lb. of fuel (one-third washed “ duff ” and two-thirds grains), the average calorific value as fired being 12,600B.Th.U. The comparative heat consumptions per watt-hour for the gas and steam stations are :— Annualload B.Th.U. per factor. watt-hour. Per cent. Average. Gas ................. 72 ... 18’0 Live steam .......... 47 ... 36’5 (To be continued.)