Lightships and Lighthouses

by Frederick Arthur Ambrose Talbot

The construction and the principle of operation are exceedingly simple, as may be gathered from reference to [Fig. 16]. The beacon comprises a gas generator tube of steel (1), which is supported by the steel float chamber (2), on the upper side of which is placed the support (3) carrying the lantern (4). Stability is insured by means of the counterweight (6) attached to the lower end of the generator tube. A few feet from the bottom of the latter is a diaphragm (7), fitted centrally with a conically-seated valve (8) which is mounted on a stem (9). This extends through the centre of the generator and its head (10). The upper end of the valve stem carries a hexagonal nut (11), while the stem itself at this point has a keyway cut into it. A spline is fitted into the generator head to engage the keyway, and when the nut (11) is turned to close or to open the valve, the stem itself cannot move with it, except in two directions only—up or down. The nut itself cannot be turned too far, in which event it might drop the stem and valve, as there is a stop-collar (12). Leakage of gas is prevented by a cap (14), which is screwed into the generator head and sealed with a rubber washer. This cap is sufficiently long to permit the valve stem to be raised or lowered so as to adjust the movement of the valve. The stem of the valve is protected from the carbide by enclosure within a tube (13), which works through a guide bar (24) bolted to the side of the generator tube. A grid (23) is fitted in the centre of the diaphragm (7) and surrounding the valve (8), so as to prevent small pieces of carbide, which may pass through the grate (16), from falling into the water, and thereby being wasted. The steel grate upon which the carbide rests is attached to the inside of the generator, a short distance above the diaphragm. The grid (23) also acts as a valve seat, and is provided with a rubber packing (15), which is held in a groove in the seat, and projects a sufficient distance to make a good joint with the valve (8) when it is closed, even if the valve happen to be foul.

The carbide of calcium, in the form of large crystals measuring about 8 by 4 inches, is placed in the generator tube when the beacon is immersed in the water, the valve (8) being opened and the valve-cap (14) screwed down. In the centre of the counterweight (6) is an orifice through which the water enters from the outside, and passes through the open valve, to come into contact with the carbide resting upon the grate. Gas is generated instantly, to ascend through the carbide into the purifying chamber (5), where all deleterious matter is removed, the gas escaping thence through the small aperture (17) and pipe (18) to the lantern, to which the supply-pipe is connected by the aid of the coupling (19).

Of course, at times gas is liable to be generated more rapidly than it can be consumed. What happens? The apparatus is not provided with facilities to receive the surplus gas. Being unable to escape upwards through the generator tube, it collects at the bottom, and as the pressure increases it gradually forces the water away from the carbide, so that generation ceases, and is not resumed until the surplus gas has been absorbed, when the water once more is able to come into contact with the carbide. Thus it will be seen that the gas generation is controlled automatically, and that it is almost impossible for the gas pressure within the plant to reach a disruptive degree, owing to the fact that when it exceeds a certain limit it has a free vent from the bottom of the device, where the water normally is permitted to enter to carry out its designed purpose.

This invention has been utilized for a wide variety of purposes, from the lighting of harbours, navigable channels, rivers, bays, and so forth, to that of exposed coasts. The automatic beacon, properly so called, has a tower, which brings the focal plane to an elevation varying between 50 and 100 feet, this tower being built of lattice steelwork attached to the top half of the buoy, with a day mark surrounding the lantern gallery, access to which is secured by an iron ladder. This type of light carries a sufficient storage of carbide in a single charge to keep the light burning continuously for about forty weeks. In this instance the only modification from that already described is that the water for the production of the gas is admitted into the top instead of to the bottom of the generator. When an excess of gas occurs, the pressure thereof drives the water away from the carbide until the surplus has been consumed. Another type, somewhat smaller, carrying a charge sufficient for nearly six months, has proved highly successful as a coastal light, some thirty beacons of this class being stationed along the shore of British Columbia. The only trouble experienced therewith in these waters has been due to frost, which, solidifying the water around the buoy, has interrupted the designed functions.

But probably the most complete and useful type of Willson acetylene gas beacon is that in which the Courtenay whistling device is incorporated, so that in thick weather audible warning of the danger may be extended. In this instance the floating chamber which supports the superstructure carrying the light and also the generator tube, is fitted with two further tubes which project from the base like huge legs. These tubes are open at the bottom, but are closed at the top except for a connection with a valve-casing, which is fitted with a ball-valve, and upon which a powerful whistle is bolted. Now, if the buoy is lowered and anchored in absolutely still water, the water will rise to the same level within the tubes as it is outside; but when the buoy is lifted upon the crest of a wave, the level of the water falls, so that the air space within the tubes is increased. Air enters this augmented space through the ball-check inlet valve in the valve-casing. When the beacon falls, naturally the water endeavours to maintain its level within the tubes, and therefore the air which was admitted into the space becomes compressed, to be expelled through the only possible vent—the whistle—thereby producing a very powerful blast. Thirty of these combined light and whistling buoys have been strung along the rugged Nova Scotia coast, and have proved highly popular, that outside Halifax harbour being known colloquially among seafarers as the “Outer Automatic.”

Another acetylene system, but working upon a better principle, has been perfected in Sweden, and, indeed, now has been adopted universally, owing to its many excellent features. This is the “Aga” light, which is the invention of Mr. Gustaf Dalén,[C] and which has been brought to a high stage of commercial success by the Gas Accumulator Company of Stockholm. I have pointed out the one objection to the Willson acetylene automatic light—namely, its uselessness when the surrounding water becomes frozen. While this drawback does not affect its sphere of utility to a noticeable degree in Canadian waters, it acts somewhat adversely in other seas where similar conditions prevail, but where the navigable channels are kept open by ice-breakers, such as, for instance, in the Baltic Sea. Mr. Dalén recognized this weak point in any system wherein contact with water is responsible for the generation of the gas, and accordingly sought for a superior method. Fortunately, the perfection of a new means of handling acetylene, by French inventors, offered the complete solution of the problem in a practical way. The principle of this lies in the use of dissolved acetylene, which is perfectly safe from explosion, and can be handled with the greatest facility. The gas can be stored in cylinders similar to those used for containing oxygen and hydrogen under pressure, gases which are easier to transport than carbide of calcium, and, what is far more important, climatic conditions do not exercise the slightest influence upon it.

[C] The humane labours of Mr. Dalén received recognition by the award of the Nobel Peace Prize in 1912.

Dissolved acetylene may be stored within the cylinder, or accumulator, as it is called, to a pressure of at least ten atmospheres, and at this pressure it contains 100 times its own volume of acetylene gas. The accumulators may be made of any desired size, this factor being governed by considerations of transport and application, as well as of the consumption of the burner.

The perfection of the dissolved acetylene process came as a great boon to the Swedish lighting authorities, inasmuch as they have probably the most difficult stretch of coastline in the world to protect. At the same time, owing to the wild, exposed character of many of the points which demanded lighting, a perfect, economical, and reliable automatic system was in urgent demand. Acetylene was an obvious illuminant, since, while the country is deficient in the essential resources for the preparation of other fuels, carbide of calcium is very cheap, Sweden, in fact, being the largest producer of this commodity. The Swedish Board of Pilotage experimented with acetylene lighting for six or seven years, submitting every known acetylene lighting system to searching practical trials, but failed to be sufficiently convinced on the vital question of reliability. Freezing-up was the most pronounced shortcoming, but when dissolved acetylene appeared as a commercial product this disadvantage was removed completely, and acetylene was adopted.