222. The Princess Louise Coil Grate.
The Princess Louise coil grate was awarded the First Prize at the Smoke Abatement Exhibition, in 1882, for giving the greatest amount of heat per lb. of coal consumed. It is now improved so as to burn 18 to 20 hours without attention; hence it is possible to heat a greenhouse or conservatory from one’s own fireside, and in fact to obtain all the hot-water for the baths, &c., of a household for no extra expense. It is shown in front view in Fig. 222, and can be seen in action at S. Deards’s show rooms, 11, North Buildings, Eldon Street, Liverpool Street, London, and at Harlow, Essex.
The “Acme” small bore pipe apparatus (The Acme Ventilating and Heating Co., 35, Tarleton Street, Liverpool) is one of the most economical, rapid, and perfect systems of heating. This system consists of strong wrought-iron tubes of best quality procurable, of 15/16 in. external diameter and ⅞ in. bore, the ends of which are provided with right and left hand threaded screws. They are connected together right and left hand, which, when screwed up, brings the coned end of one tube into the flattened end of the other, thus making a perfectly sound hydraulic joint—in fact, such joint is actually stronger than the tube itself, the threaded screws are not intended to make any joint excepting by the power applied in forcing the conical end to the opposite flat end of tube, which generally makes an indentation of about 1/16 in.: this forms the joint, the cone making its own seat, and when once fitted, water has no access to the screw in the socket, which, therefore, cannot rust, and may be unscrewed at any time without trouble. This joint is not affected by expansion and contraction, which is a constant source of annoyance and expense where the ordinary form of joint is used, as with the large cast-iron hot water pipes used in the low pressure systems. The “Acme” system offers the further advantage of readily allowing any tube to be disconnected and removed without disturbing the rest.
A large portion of the said tubes form the boiler or furnace, which, being fixed at the lowest level, forms one of the most rapid and economical furnaces known. Smaller furnaces, with wrought or cast-iron casings, with coils of pipes built in fire-bricks, are used for small buildings, halls, corridors, or offices.
An ordinary fire-grate may be utilised by a few feet of piping being coiled and placed in same, forming the fire-bars and back of grate, which constitutes a boiler in itself, and is connected with other piping connecting with adjacent apartments. As many as three or four bedrooms, or a suite of offices, may be comfortably heated from the one fire.
The apparatus consists of an endless circuit of strong wrought-iron tubes (all of the same diameter), filled with water. It is thoroughly tested under a hydraulic pressure of about 3000 lb. per sq. in., so as to ensure that the joints, and all parts of the apparatus, are perfectly safe and sound. The fire being lighted, the water circulation commences, as the water in the furnace-coil becomes heated, it ascends to the top of the apparatus, whilst the cold water, being heavier, descends, to supply the place of the ascending heated water, and thus a continuous circulation of hot water is kept up, which rapidly increases in velocity, through the pipes, as the heat in the furnace becomes greater. The tubes are kept absolutely full without the possibility of a higher pressure than that at which the expansion valve is set, and this setting corresponds with the temperature the pipes are intended to give off. As will be seen, a very large margin of safety is provided for in every case, much beyond the maximum pressure by heat that can possibly be obtained. Formation of steam is impossible, as is also the stoppage of the circulation through air locking.
The superior quality and small diameter of the tubes, and the ready manner in which they can be bent, makes it the most complete system extant. The “Acme” apparatus is equally well adapted to old or new buildings, as it may be introduced without disturbance of existing arrangements, and does not necessarily require the construction of trenches or channels, an inconvenience in other systems which often prevents their adoption. The preliminary expenses in introducing the “Acme” system are very trifling, and as the circulation does not depend upon the tubes being laid at an incline, the apparatus is not unsightly or in the way.
All the difficulties arising from condensation, air stoppage, and the consequent necessity for attention to valves and air-cocks (as in other systems) are avoided—so simple, indeed, is the apparatus that it may safely be left to the care of any ordinary house-servant. Fixed close to the expansion (or safety) tube is another tube for supplying the apparatus with water. Beyond the necessity of attending to the furnace, it is only requisite to see that the tube is supplied with a proper quantity of water about once a week (when in constant operation), this, in an ordinary sized apparatus, is about ½ pint. If this arrangement is not convenient, a small cistern of sufficient capacity to hold the expanded water can be fixed, inside of which is placed an expansion and in-take valve. The expansion tube and the water supply pipe are so arranged that when the water is level with the top of the filling pipe it is only up to the bottom of the expansion tube, leaving the whole of the tube empty. It is, therefore, impossible to fill the tube by pouring water into it, the expansion tube being always empty when the apparatus is cold. Before the fire is lit, the apparatus is filled with water, and the two screw-plugs seal them; as the water rises in the tube, when the furnace becomes heated, it compresses the air that is left in it, and so automatically regulates the pressure that no undue strain is put upon the apparatus.
Instances are known where Acme apparatus have been in use for over 20 years without entailing the least expense for repairs. When erected, they are tested by hydraulic means to a pressure of 150 atmospheres, and the valve is regulated to blow off at six atmospheres—it is manifest that, with proper care, leaks or accidents are of very rare occurrence. The material throughout being of best wrought iron, breakage is impossible, even with the roughest usage; hence the cost of maintenance, often such a heavy item incidental to other systems, is avoided. With the “Acme” system repairs are practically nil; further there is no trouble and no sulphurous smells. Where trouble and expense have been experienced with small pipes, they have invariably been the result of bad workmanship, or of neglect by the attendant of the simple instructions given.