Crown Agents' Bulletin No. 4
CONFIDENTIAL.
37
VII. PREPARATION OF BITUMINOUS
EMULSION FOR ROAD SURFACING.
Considerable quantities of various proprietary brands of bituminous emulsion for use in surfacing roads oversea are sent out by the Crown Agents annually. These preparations are usually expensive and extremely bulky and therefore the freight charges are also heavy. From one-third to one-half of the total bulk of these preparations usually consists of water and consequently it will be seen that if it were possible for oversea Administrations to make their emulsions on the spot the cost to the Governments concerned would be materially reduced.
The Trinidad Lake Asphalt Operating Co. Ltd. have recently designed apparatus of moderate cost for making a suitable emulsion and the following particulars will doubtless be found of interest.
The plant is capable of turning out about 2,500 Imperial gallons of emulsion per day. The mixer consists of a cylindrical tank 4 ft. high by 3 ft. 6 in. diameter standing on four legs and having an outer casing of sheet metal to retain the heat. (See Plate XXII). This vessel has a vertical central shaft fitted with two sets of horizontal blades (canted at 45° from the vertical in order to give an upward thrust to the liquid), and two sets of stationary blades mounted on angle irons on the sides of the mixing tank, the angles being located on opposite ends of one diameter of the tank. The fixed and moving blades are so spaced that one row of revolving blades passes a row of stationary blades with about 1 in. clearance between top and bottom. The vertical shaft revolves at about 25 r.p.m. The actual capacity of the mixer is approximately 240 Imperial gallons but the working capacity is 125 Imperial gallons. The considerable difference between actual and work- -ing capacity is designed to prevent difficulty arising from the foaming which will occur when water is first introduced into the mixer. As further water is introduced the foaming will subside.
The mixer is arranged to stand on legs giving a clearance from the under side of the mixer to the ground of not less than 2 ft., while the outer casing should extend down a further 12 inches. Underneath is located a burner outfit of the fire pot type consuming approximately 8th of a gallon of fuel per hour.
The flame should not be allowed to impinge upon the metal of the mixer shell as this would cause local overheating and might give rise to buckling of the plate.
From 5 to 6 b.h.p. has been found ample to drive the machine and a suitable petrol engine or electric motor may be used. The size of pulley will be determined by the speed of the motor and the size of the fast and loose pulleys on the mixer.
RAW MATERIALS FOR AND METHOD OF PRODUCING TRINIDAD LAKE ASPHALT
EMULSION.
For the production of 2,500 Imperial gallons of emulsion per day the following raw materials are required:-
Refined Trinidad Lake Asphalt
Flux
Soap Water
...
12,146 lb.
...
3,037,,
1,482,,
1,125 Imperial gallons.
The Crown Agents' Bulletin No. 4 (Confidential).
15