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concrete, including plums, to be placed amounted to 180,000 cubic yards about 150,000 cubic yards of concrete, allowing for 20% plums, and this was to be accomplished in about 2 years. Allow- ing for no Sunday work, inclement wea- ther and only one working shift per day, the number of actual working days was estimated to be 270 per year, or 540 in two years.
(The actual number of work- ing days in 1954 and 1955 proved to be 270 and 290 respectively.) Thus, ап average of 275 cubic yards per day should be placed. To achieve this figure, allow- ance must be made for a building up in the rate of placing from, a possible 150 cubic yards initially, to a maximum of 400 cubic yards. The concrete batching plant must be capable, then, of producing à maximum daily output of 400 cubic yards per shift, or at a rate of at least 40 cubic yards per hour for a 10 hour
shift.
To meet this requirement, а concrete weigh batching plant comprising essen tially two cubic-yard mixers, a 60-ton capacity storage hopper, weigh hopper, and a 12-ton per hour cement elevator was ordered from Messrs. Stothert and Pitt Ltd. which according to the makers should produce a maximum output of 68 cubic yards per hour. This figure could not be achieved, as the stone-crushing plant as designed could not
quite provide the aggregate for this amount Aggregates in the sizes specified, nominal 3/8 inch, 3/4 inch, 1 inch and 3 inch and sand, would be stored in a 5-compart ment hopper of 60 tons capacity, sufficient for more than an hour's work at maximum output.
10-Ton Cableway
The travelling hend carriage of the cableway,
the speed of hooking and unhooking the concrete skip and of discharging the con- crete from the skip. Theoretically, the cableway should be capable of making 12 the required 40 cubic yards per hour. round trips per hour, thus easily handling
both the hoist and travel ropes can be coiled-in or paid-out to the same extent in order that the hoisting block can travel parallel to the main cable.
Erection of the cableway was com- menced in early February 1954 and sub. stantially completed in early July 1954. This work was carried out under the direction of two erectors, who were specially flown out to Hong Kong from Scotland. The z-inch diameter main cable, weighing tons, was dragged across the valley over the dam foundation by one of the Fordson Major tractors in a little over 36 hours.
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Quarry Stone-crushing Plant
To produce the maximum output of 400 cubic yards of 1:5:7 of Class C con- crete (which is the mix for the inass con- crete) per IO hour shift, using 2 inch straight crusher run, together with natural sand and crusher fines in the proportion of 2 parts sand to part crusher fines, in place of the screened stone aggregate, and allowing for 10% fines in the crusher run (obtained from sieve tests), it was found that the following materials would be required:
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180
tons cement per shift, or 5 tons per hour.
tons natural sand per shift, or 18 tons per hour.
48 tons crusher fines per shift or 5
tons per hour.
420
tons crusher run per shift, or 42 tons per hour.
The cableway consists essentially of a fixed tailmast. and travelling head car- riage, with
For the production of this quantity of a steel wire cable spanning between them. A load carriage, mounted crushed stone in various gradings from 3
inches downwards, a For placing the concrete in the dam at on grooved track wheels and carrying a
standard quarry the required rate of 40 cubic yards per hoisting block, is travelled backwards and stone crushing plant was purchased from hour, a ro-ton electric radial cableway forwards on the cable by an endless steel Messrs. Frederick Parker Ltd. The major was ordered from Messrs. J. M. Hender- wire rope, known as the travel rope, and items of this plant are two 24" x 15" Son & Co., Ltd., and three 4 cubic- the load is hoisted and lowered by a stone crushers giving a total rated capa- yard concrete skips were ordered from further rope, known as the hoist rope. city of 60 tons of crushed stone per hour, Messrs. Blaw-Knox Ltd. With hoisting reeved between pulleys on the hoisting two 36" x 6" granulators and one 22" x and travelling speeds of 250 and 1,000 block and carriage. The travel and hoist 16" crushing roll for the production of feet per minute respectively, the time to ropes are lead from the load carriage over the smaller aggregate and crusher fines, complete one round trip from the batch- guide pulleys on the head carriage to ar screens for the different gradings, four VE ing plant to the farthest part of the dam electrically-driven winch fitted with travel 85 bin units of 400 tons total capacity, a distance of 1,000 feet and with a and hoist drums, operated by a 250 H.P. and belt conveyors and bucket elevators hoist of about 120 feet. would be around slip-ring motor through friction clutches for handling the materials within the 5 minutes, this time being dependent upon The two drums are the same size so that plant.
PATERSON
RAPID GRAVITY
FILTRATION
TREATMENT PLANT BEING INSTALLED AT TSUN WAN
AS PART OF THE TAI LAM CHUNG SCHEME
viliary diesel driven generator set.
au-
The plant now being installed at Tsun twelve gravity filters, filtered water tanks. a drop tube to enter the flocculating tanks Wan to treat water from the Tai Lam alumina dosing equipment, lime dosing at floor level. From here the water rises Chung Reservoir is designed for an im- equipment, chlorine sterilising equipment, through slowly revolving paddles to the mediate duty of 20 million galls per day machinery for filter cleansing and an inlet distribution and for extension to 40 million galls per day by the addition of 12 further filters. The Paterson Engineering Company have now been entrusted with the contract to supply plant and machinery for the ex- tension, and installation will follow com- pletion and setting to work of the present plant.
The present plant consists of an inlet measuring flume, two flocculating tanks,
filtra- channels of the tion system. Entering the filters the water percolates through the filter bed where it Raw water from the Tai Lam Chung is collected into a central header channel impounding reservoir will be pumped from and discharged through the Venturi out- the Tsun Wan pumping station to enter let controllers to the filtered water chan- the plant at the measuring flume con- nel, constructed below the lower operating structed on the side wall of No. 1. floc- gallery, where it is treated with chlorine culating tank. Whilst passing through the and a further dose of lime. The water flume the raw water receives doses of al- then flows over a retaining weir and thence umina and lime in direct proportion to through control penstocks into either or the flow and is then conducted through both haives of the storage tank from
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