December 11, 1914. THE COLLIER! GUARDIAN. 1221 ___________________________________________________________________________________________________________________________________________________________________________________________ into operation until b has travelled sufficiently far towards the right to push in the spindle /, there being a certain amount of play left to allow the governor to first close the throttle valve E (fig. 5) through the lever b, a, e, before opening the air valve. The tension of the spring in the air valve may be adjusted by means of the nuts on the spindle /. When the load is suddenly thrown off the centrifugal governor will first close the throttle valve, but may leave sufficient residual steam in the steam chest of the turbine to cause a still further increase of speed. The lever b will then move sufficiently far to the right to strike the valve spindle f, thus opening the air valve and admitting air to the under side of the piston T. This will cause the butterfly valve to assume the posi- tion shown by the dotted lines (fig. 5), thus causing a momentary back pressure, which quickly reduces the speed of the turbine wheel, and as there is sufficient play between the piston T and the walls of its cylinder to allow the air to pass into the exhaust (which is under vacuum), the piston is free to return to its normal posi- tion as soon as the speed drops sufficiently to allow the air valve to close again. By this device the speed does not vary by more than from 1| to 2 per cent. Gearing. The speed of the turbine wheel being 7,830 revolutions per minute, it is reduced down about 10-4 to 1 on the armature shaft by means of double helical gearing, spirally cut, which ensures noiseless and smooth run- geared down to 1,500 revolutions per mipute on the pump shaft. Steam is supplied to this turbine direct from the boilers at 80 lb. per sq. in. pressure through eight nozzles. There is also forced lubrication and oil cooling, similar to that provided for the bigger set, and previously described. This plant produces a vacuum of 27 in. when the mixed pressure turbine set is running on full load and with the low-pressure exhaust steam, while the vacuum rises to 27| in. in the event of the high-pressure steam being used. The centrifugal pump a Vacuum Governor Centrifugal Governor Air Valve pump at the pit bottom, which pumps 10,000 galls, of water per hour against a head of 870 ft., and also pro- vides the power for the main rope haulage in the Seven Feet seam. Current is also conveyed from this pit to No. 4 Pit, situated about a mile away, the current being conveyed by means of bare aluminium cables, where power is supplied to a pump at the pit bottom, which deals with 10,000 galls, of water against a head of 480 ft., and also works the main endless rope haulage, which has a length of 1,200 yds., and hauls 600 tons of coal per day To Turbine Exhaust Chamber cc o z cc. LxJ cc' => o => z o tc Fig. 4—Air Valve. Fig. 6—Section of Gear-case, Showing Oil Pump. Z ning, notwithstanding the high speed and the power transmitted. Contained in the gear case is a small rotary oil pump Q (fig. 6), giving forced lubrication to the bearings of the turbine shaft, and worked from the armature shaft by means of a worm and worm wheel V. The pump draws its oil from the oil sump U, which is neatly incorporated in the bedplate of the turbine set. In addition to this, the oil is cooled by means of the spiral W, through which cold water circulates by the pipes Y and Z, the oil being filtered before passing into that part of the sump containing the oil pump. Generator. This is a 300 kw. direct current generator, six pole, 750 revolutions per minute, with commutating poles. The generator is wound for 530 volts for supplying cur- rent in the immediate vicinity, but as part of the current is required for No. 4 pit, situated about one mile away, this portion of the current is passed through a series-wound booster, direct coupled to the generator, which exactly compensates for the drop in the transmission line, and raises the pressure to 630 volts at the maximum current. This scheme was adopted in preference to a.c. high- tension transmission with static transformer, as it was equally efficient, whilst being cheaper and simpler. Condenser. The condenser which deals with the exhaust steam from the turbine is of the Mirrlees-Leblanc type, with a rotary air pump and centrifugal water pump. These are driven by means of a small De Laval type turbine, running at 15,000 revolutions per minute, but is capable of dealing with 770 galls, of water per minute at 75 degs. Fahr., there being a natural draught chimney cooling tower capable of cooling 55,000 galls, of water per hour from a temperature of 111 degs. Fahr, down to 75 degs. Fahr. The condenser is shown in fig. 7. Economy. In spite of the belief that only big turbine sets utilising exhaust steam are economical, it may be men- tioned that the economy of this small plant is very high, the figure guaranteed by Messrs. Greenwood and Batley for this type of plant when working at full load being 431b. of exhaust steam per kw. hour, with an initial pressure of 1 lb. per sq. in. above atmospheric pressure, and a vacuum of 27 in.,-but as a matter of fact, on actual Fig. 7—Condenser plant at Griff Colliery. tests of the plant at the Griff Colliery, the consumption of steam was found to be considerably lower than this, and that there was little difference down to half-load. This mixed pressure plant has been arranged for future duplication, it being intended subsequently to utilise the exhaust steam from the winding engine. At present this plant replaces two 170 kw. sets, driven by high- pressure steam, and supplies current to a Hathorn-Davey up a gradient of 1 in 7, besides working two small endless rope haulages, and a three-throw ram pump, which pumps 3,000 galls, of water per hour, against a head of 450 ft. out of the dip -workings. _________________________ United States Imports and Exports.—The following is a comparative statement of imports and exports of the United States for September 1913-14, and for the nine months ending September 1912-13-14, in long tons :—- Nine months. Septern her. Imports from: 1912. 1913. 1914. ' 1913. 1914. United Kingdom 4,062 . 4,597 . 8,410 904 .. 102 Canada 1,050,394 . .. 828,013 . 771,158 . 81,984... 101,646 Japan Australia and Tas- 20,228.. .. 79,075.. 44,539. 8,843 .. 90 mania 108,925 . 121,386 . 164,121 24,735 26,933 Other countries ... 2,025.. 2,816. 2,053. — ... — Total Exports: 1,185,631 1,035,887 . . 990,284 116,469... 128,771 Anthracite. Canada 2,551,589.. . 3,119,522 . . 3,017,158 . . 319,410 .. .‘189,213 Brazil .—— 6 . — ... 6 Other countries .. 50,042.. 53,480... 44,893 . 6,149 .. 5,869 Total Bituminous. 2,601,631.. . 3,173,002 3,062,057.. . 325,559... 395,088 Canada 7,766,198 . 10,281,998 . 7,211,856 . 1,631,526 1,202,930 Panama ... 362,277. 387,582 . 214,131 35,732... 23,166 Mexico 239,402 . . 397,753. . 257,380 . 20,655.. 42,312 Cuba 851,389 . . 983,392 . 793,898 . . 115,278 . 97,787 West Indies 506,624 . 464,645 . . 479,895 . 45,149... 64,099 Argentina 55,877 .. 211,045 . 5,163. 193,786. 201,071. 61,443 . 7,251 .. 55,567 10,957... 45,846 . — ... 4,929 Brazil Uruguay — Other countries... 1,257,403 . . 1,004,508 .. 1,459,320.. 92,904 .. 320,884 Total 10,983,293 . 13,793,963 . 5,763,584 . 10,902,780 1,959,452 .1,857,520 Bunker coal 5,495,719 . 5,711,918 . . 684,395 .. 673,372 Exports and Imports of Mining Machinery.—The values of imports and exports of mining machinery during November were as follow :— November. Jan.-Nov. ?913. 1914? 1913. 1914? £ £ £ £ Imports........ 12,592 ... 4,906 ... 109,708 . . 94,440 Exports........ 72,930 ... 53,267 .. 959,196 . 772,031 It should be mentioned that these figures do not include prime movers or electrical machinery. According to destina- tion, the value of exports was as follows :— November. Jan -Nov. 1913 1914. ' 1913 1914? To— £ £ £ £ Countries in Europe........ 6,652... 2,934... 98.918...138,421 United States of America ... 10.. 190... 2,638... 1,1'90 Countries in South America 4,314... 3,503... 68,683... 59,017 British South Africa ...... 26,187...18,119. .397,886.. 266,367 ,. East Indies ...... 13,918... 7,077... 98,195... 78,361 Australia ................... 5,934... 3,405 . 39,338 . 40,321 New Zealand .............. 2,071... 464... 25,914... 13,354 Other countries .......... 13,844...17,575...227,624..175,100 The following shows exports of prime movers other than electrical :— November. Jan.-Nov. _______ 1913. 19'4? 1913. 19'4. All prime movers £ £ £ £ (except electrical) 828,459... 652,492 .. 9,237,071... 9,518,592 Rail locomotives ... 267,560... 356,798... 2,579,123... 3,654.840 Humping.......... 43,863... 22,334 626,754... 432,621 Winding .......... 2,094 . 499... 22,720... 26,193