The Preparation of Plantation Rubber Part 20

[Ill.u.s.tration: "THIRD MILE" TYPE OF SMOKE-HOUSE.]

In essence the design consists of a building, having two storeys for rubber-drying, and a shallow inverted pyramidal base, ending on the ground in "Third Mile" furnace, already described and ill.u.s.trated.

It will be seen that the principles of ventilation employed are those indicated for an ordinary house--viz., air-inlet near the ground (with little draught), and smoke-vent at the roof-ridge. The windows shown in the drawing are only for purposes of inspection of the rubber during the day, and form no part of the scheme of ventilation during the hours of smoking.

It is claimed that the efficiency of the house is high. Certainly the work of attending to the furnaces is simplified, and there should be small ground for excuse if negligence is displayed.

JACKSON HOUSE.--This was brought into notice under the description of the "Jackson Cabinet," and it was claimed that average sheets could be dried in a few days. It consisted of a small house of one storey, having several tiers of racks. Smoke and heat were generated in a small stove placed outside the wall. A smoke vent was provided in the roof. These cabinets had a certain vogue as part of a small unit installation, with a fair degree of success. It is not clear, however, that such speed in drying is required.

(This point will receive further attention in a subsequent chapter.)

"DEVON" TYPE.--In its full original design this type owes its origin to Mr.

H. E. Nixon, General Manager of the Devon Estates, Malacca, where it forms part of unit divisional installations worked under a scheme of decentralisation.

The original units consisted of a building erected with an iron framework covered with sheets of asbestos-slate, and a roof of galvanised iron.

The novelty in design lies in the utilisation of external platforms upon which the racks of bars supporting the sheets of rubber may be drawn out of the smoking chambers, and on which the racks are loaded and unloaded. By this device it is possible to remove the contents of any compartment bodily without interfering with the continuity of curing in the other compartments. That is to say, smoking in such a house can proceed day and night if necessary, and yet the rubber in any part of the house can be examined, can be removed, or can be replaced without cessation of smoking.

It will be seen from the ill.u.s.trations that the house is more or less of the same general design as the "Third Mile" type, with the addition of external platforms. It has two storeys for the reception of rubber; and a basal furnace-room with sloping sides converging downwards into a pit containing a large drum-furnace. This is mounted on a low truck, and travels on a short length of railway.

[Ill.u.s.tration: GENERAL VIEW OF DOUBLE "DEVON" TYPE OF SMOKE-HOUSE.

The platforms are common to both units. Building of brick with iron roof (Batu Caves Estate).]

Each of the curing-rooms is divided into four compartments (making eight compartments in all). These are closed by swing doors, each of which is the full width of a compartment, and has a slight overlapping edge. Through these doors light railways run into the house and out upon the platforms.

On the rails "bays" of racks run, and when fully loaded they are easily moved. The racks were designed with a frame of stout hard wood, but light angle-iron could be utilised.

[Ill.u.s.tration: GENERAL VIEW OF DOUBLE "DEVON" SMOKE-HOUSE AND FACTORY BUILDINGS.

Timber in foreground cut to length for stoking. Note water-tower and engine cooling-tanks adjacent to factory.]

The chimney style of smoke-vent has an internal b.u.t.terfly flap, which is controlled by means of a wire from the outside. In the ordinary course of smoke-curing, it is advised that this flap should be permanently open so as to reduce the possibility of internal condensation of moisture and creosotic matter. The exact degree to which it should be open must be found by experience.

[Ill.u.s.tration: VIEW OF PLATFORM OF "DEVON" SMOKE-HOUSE; DOORS OF COMPARTMENTS OPEN, AND ONE RACK PARTIALLY WITHDRAWN.

Note below each rack opening through which smoke rises, covered with wire netting.]

Although reference has been made several times to compartments, it should be understood that the chambers are not subdivided internally by means of part.i.tions. There exists only the external effect of compartments in the form of the eight swinging doors which allow for the withdrawal of, or insertion of, any one unit of racks at any time without interference with the bulk of the rubber.

[Ill.u.s.tration: DOUBLE "DEVON" SMOKE-HOUSE OF BRICK, WITH ROOF OF CHINESE TILES, SHOWING LOADING PLATFORMS WITH RACKS WITHDRAWN FROM SMOKING CHAMBERS.

Federated Engineering Co., Ltd., Kuala Lumpur.]

[Ill.u.s.tration: SIDE VIEW OF PRECEDING PHOTOGRAPH, SHOWING EXTERNAL ARRANGEMENT FOR STOKING FURNACES.

Federated Engineering Co., Ltd., Kuala Lumpur.]

DETAILED DESCRIPTION.--As enquiries are often received it is permissible to reproduce the following detailed description of the original house. This appeared in the Fourth Local Report (Malaya) 1916, issued to subscribers by the Rubber Growers' a.s.sociation.

"The house has a steel frame-work, 22 feet long, 16 feet wide, and 22 feet high. Of the length, 14 feet is occupied by the platforms, and 8 feet by the chambers. These measurements can be varied. The whole of the width (16 feet) is occupied by compartments of which one series is placed above the other.

[Ill.u.s.tration: FRONT VIEW OF DOUBLE "DEVON" TYPE OF SMOKE-HOUSE.

Glenmarie Estate: Batu Tiga Co.]

"_Platforms._--The loading verandahs or platforms are of ordinary 'seriah' timber.

"_Compartments and Furnace Chamber._--These are enclosed with Bell's 'Poilite' sheets, each of which measures 8 feet by 4 feet by 3/16 inch. The sheets are affixed to the steel stanchions, doors, etc., by galvanised bolts (1 inch by 1/4 inch) which pa.s.s through iron flats measuring 8 feet by 2 inches by 3/8 inch (about). These iron flats hold the sheets at the edges. The dimensions of the compartments are 8 feet by 8 feet by 4 feet.

"_Racks._--These are eight in number, and measure just under 8 feet by 8 feet by 4 feet. The capacity of each is roughly about 450 lbs., of dry sheet rubber. The racks are mounted on 6-inch iron wheels, running on rails of stock size, 'T' iron (1-3/4 inches by 1-3/4 inches by 1/4 inch).

"The sheets are hung on split bamboos. To prevent these projecting over the edge of the rack and catching in the doors when the rack is moved in or out, a thin strip of wood, about 1/2 inch high, is nailed along the sides of the rack.

[Ill.u.s.tration: SIDE VIEW OF DOUBLE "DEVON" TYPE OF SMOKE-HOUSE.

Building constructed of galvanised iron. Shows door to furnace chamber, and ventilator.]

"_Furnace._--This is of the type that aims at slow combustion. It consists of a cast-iron cylinder, 3 feet in diameter and 4 feet high, carried on a truck made of a sheet of boiler-plate, and mounted on small wheels, so that the whole can be moved easily out of, and into, the furnace chamber for easy cleaning and stoking.

"The furnace chamber is a pit lined with concrete, just wide enough to take the trolley, and about 12 feet long. The top of the furnace, which is almost flush with the ground-level, consists of a sheet of zinc or galvanised iron with numerous holes about 3 inches in diameter. Over these holes are strips of mosquito gauze, as flame and dust arresters (see note below). There are no holes in the sides or bottom of the cylinder.

"Over the furnace is hung a baffle-plate, measuring 4 feet by 4 feet.

Above this, on the first floor-level, the bottom of the compartments is covered with wire netting, to prevent any rubber dropping accidentally into the furnace chamber. The furnace chamber is fitted with an iron-frame door, swinging on perpendicular hinges.

"_Method of Stoking._--The timber used is a mixture of jungle wood and rubber-tree wood, cut to lengths of about 1-1/2 feet. In the ordinary way the furnace is charged at 6 p.m., and at six-hour intervals a little more fuel is added, but a new charge is not necessary. During the daytime, when the heat of the sun is sufficient to raise the temperature appreciably, a smaller fire is maintained.

"_Temperature._--There is no difficulty in maintaining a temperature of 120 F. By continuous smoking, average sheets prepared from standardised latex can be fully cured in five days. This represents 110 hours of smoke-curing, which is at least equal to ten days'

intermittent smoking in an ordinary house.

"_Capacity._--There are eight racks, each accommodating 450 lbs. of standardised sheet rubber. The loading capacity of the house, therefore, is 3,600 lbs. As each charge is cured in five days, the monthly output may be 21,000 lbs.

"The cubic capacity is 2,048 cubic feet. As there are no gangways, etc., this is fully utilised. This gives a rate of monthly output capacity to over 10-1/4 lbs. dry rubber per cubic foot of drying s.p.a.ce; an excellent figure much in advance of values obtained in the great majority of ordinary smoke-houses."[18]

[18] Since the above was written, it has been found possible to eliminate the gauze. A mild steel top has been made, perforated with 2-inch holes.

Practically no dust is ejected from the furnace, and there are no flames.

Owing to shortage of supplies during the War, similar buildings have been erected with frames of well-seasoned hard wood, which was protected by strips of asbestos-slate or galvanised iron. The latter material was also subst.i.tuted in the covering walls. Later, houses were erected of brick, with other minor modifications. As a natural development, the latest buildings consist of two of the original houses face to face, under a common roof, and served by common platforms.

As originally designed, the house was intended to meet the needs of a small estate, or a division of an estate, having a maximum output of about 20,000 lbs. of sheet rubber per month. The possibility of an extension of this idea has been shown to be great.

The furnace has been described as situated in a pit. Situated on a bank or on sloping ground, it was easy to arrange for withdrawal of the furnace. In some cases this has not been possible, and various modifications have been effected. The most satisfactory yet encountered is that in which a shallow brick pit is surmounted by an iron cone, about 4 feet in height. This is fitted with a cap having small perforations. The fire burns in the pit, and the heat is radiated by the cone. It would have been more effective to have allowed greater height in the furnace chamber, and to have employed the travelling drum-furnace as in the original design.

In order to avoid interference in draught by a s.p.a.ce between the bottom of the doors of the compartments and the platform (due to the presence of rails), the floor of the platform is laid level with the top of the rails; or to the bottom of the doors is attached a swinging flap, notched for accommodating the rails when in position.

There are in use houses of other designs, which all more or less vary only in some modifications from the types described. Hence they do not call for special comment. Recently a rather distinct departure has been noted in a structure designated the "Barker" smoke-house.

BARKER PATENT.--In essential this consists of a long narrow structure erected with an appreciable slope from one end to the other. At the lower end is a small furnace enclosed in a brick compartment. The smoke from this furnace travels up the slope to the other end, at which the rubber enters.

The sheets are hung on bars which are attached to a unit framework. This frame slides, by its own weight, upon timber side supports. A sufficient number of these units occupies the full effective length of the structure.