The Mechanical Handling and Storing of Material

THE HANDLING OF MATERIAL BY PNEUMATLC MEANS 217 These defects having been removed, the consumption of power has been reduced to about 2 H.P. per ton of grain handled. The difference in the power consumed, between the Duckham machines built in this country and on the Continent, is to a great extent owing to the air-pumps of the Continental machines being vertical and altogether of more suitable construction than the horizontal machines which were used with the earliest Duckham machines in this country. The Most Recent Additions to the Pneumatic Grain-Handling Plant at the Millwall Docks.1—These new additions consist of a “dolphin,” elevators, and silos, together with a granary having 7| acres of open floor storage, situated at the north- west of the inner dock. The equipment provides for the discharging and weighing of 550 tons of grain per hour ex ship, and for its delivery into granary, silo, or barge. In practice about one-third goes ashore, the remaining two-thirds to craft. The pneumatic suction plant, Figs. 297 to 300, is erected on a wooden jetty 350 ft. long by 25 ft. wide on the dock side of which the ship is moored. It is placed parallel with the quay wall at a distance of 50 ft. from it. The intervening water space which is occupied by barges is spanned by four girder bridges which connect the “ dolphin ” with the delivery floor of the silo on the quay. The deck of the “dolphin” is 14 ft. above Trinity high-water mark. The sides and ends of the machine-room are built of timber and the deck of the “dolphin” forming the roof is at this part caulked with oakum and run with pitch. The boiler and engine rooms project 10 ft. above the upper deck and are cased in with steel plates. There are on the “dolphin” four suction elevators, with a capacity of 75 tons per hour each. The power is supplied to these elevators by the machinery placed within the “ dolphin,” consisting of a vertical compound condensing engine capable of developing 900 LH.P. at a pressure of 130 lb. per square inch. The power is transmitted to four pairs of exhaust pumps, (.<?., one pair to each elevator tower, by means of a 9-in. main shaft and helical gear-wheels of steel. Hydraulic pin-couplings on the shaft admit of either the north or south section being worked independently. The pumps are double acting with cylinders 46 in. in diameter by 60 in. stroke. Each pair of pumps works in tandem, the piston rods between the cylinders and also the tail ends being supported by slippers on guide bars. The pistons are of cast iron with junk rings and |-in. mica packing. The lower half circumference of each ring is of solid gun-metal of inverted T-shape with a wide flange to give greater bearing surface and reduce friction. The pump covers are of box form connecting with suction and delivery air-pipes, the air being drawn through the ports on the top half of the grid-plates, and discharged through those on the bottom. The normal speed of the pumps is 40 revs, per minute. On each elevator tower there is a vacuum chamber or grain receiver 20 ft. high and 14 ft. in diameter constructed of steel plates with internal angles and baffle fittings. The vacuum maintained in these chambers by the pumps is usually from 7 to 10 in. of mercury, but varying with different classes of grain ; the denser the grain the more complete is the vacuum required. Each receiver or “canister” has two valve branches for the connection of grain suction pipes and is coned at the lower end in the usual way and connected to automatic ! Extract from a paper entitled “ Some Recent Grain Handling and Storing Appliances at the Millwall Docks,” read by Magnus Mowat before the Institution of Civil Engineers on 2nd March 1909.