Modern Gasworks Practice

316 MODERN GAS WORKS PRACTICE outlets with. side doors are fixed at convenient intervals. Conveyors operated on this principle may be arranged with either a single or double chain, but in any case the push-plates should not be allowed to touch the bottom of the trough. For this reason, in those designs where guided rollers are not made use of, the plates are fitted with some form of skidder-bar which slides in its guides and takes the greater portion of the wear. So far as economy in motive power is concerned the roller types are to be preferred. The normal speed of these conveyors is somewliat greater than that of the tipping-tray type, and varies between 60 and 180 feet per minute. The capacity depends upon the speed, the size of the trough, and the pitch of the draw-bars. The pitcli may be anything from 18 inches to 3 feet. With the usual trough of about 2 feet in width and having push-plates at a pitch of 2 feet the capacity is normally 30 tons per hour, with an average speed of 100 feet per minute. Conveyors of this type have been somewhat generally adopted for the removal of hot coke from retort houses. When used for this purpose it must be borne in mind that the friability of the coke will not permit of a high rate of travel, if disintegration of the material is to be avoided. In the De Brouwer hot coke conveyor the average rate of travel does not exceed 40 feet per minute. Push-plate conveyors are very convenient for dealing with small coal owing to the ease with which the point of discharge can be altered, while by partly opening some of the discharge doors the coal can be discharged simultaneously at two or three points. The capacity of a 2 feet wide conveyor (placed horizontally) with scrapers or push-plates two feet apart would be approximately 150 tons per hour at a speed of 100 feet per minute. A reduction in capacity results from placing the conveyor on a slope, the falling off amounting to about 16 per cent, for each 10° inclination. Lister gives the following figures in Connection with the capacity of push-plate conveyors when dealing with coal and running at a speed of 100 feet per minute. Capacity of Push-Plate Conveyors Size of Push-Plates. Distance Apart of Push-Plates. 16 in. 18 in. 24 in. 10 in. wide x 4 in. deep . 30 27 20 tons per hour 12 in. „ X 5 in. » • 45 40 30 » » » 18 in. „ X 6 in. » • —■ 70 50 » » » 20 in. „ X 8 in. „ • — — 90 » 5? >> 24 in. „ X 10 in. . . . — — 150 » » {Note.—Above capaoities refer to horizontal conveyors. For inclined conveyors deduct 16 per cent, from capacity for every 10 degrees rise from horizontal.) Gravity-Bucket Conveyors The gravity-bucket or travelling-bucket conveyor has for some years been a foremost favourite in America, and is now assuming some considerable importance in this country. Briefly described, it consists of two entliess chains held apart at a predetermined distance by suitable bars, to each end of which. is fixed a small roller, these rollers running along special guide-tracks. The distance pieces between