The Care of Steam-Wagon Boilers.
Page 18
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Contributed by an Enginecn-in-Charge.
The life of a steam-wagon boiler depends upon three things (t) the quality of the materials used in construction ; (2) the workmanship ; and (3) the care bestowed upon it by the driver. A boiler will deteriorate more during 12 months' use in the hands of a careless man than during four years' use in the hands of a careful man who takes an interest in it. Because most jobs connected with a boiler are dirty jobs, and to many men are uninteresting, they are often neglected until matters become serious and a lot of damage has been done.
It is, unfortunately, a prevalent idea with owners of steam wagons, and, in fact, with owners of other boilers as well, that any man who can " hit the furnace mouth " with a shovel of coals is good enough for a fireman ; but this is a mistake, as a great deal of harm ensues from the employment of such men. The firing should be done at regular intervals, and the fire-door should be kept open as little as possible, for any cold air rushing through the fire-door on to the tube-plate is liable to CAUSE LEAKY TUBES owing to the contraction; the same risk occurs in checking the steam by keeping the fire-door open, a course which, in many eases, can be avoided. While running, the fire is often allowed to burn in holes, especially at the sides and corners of the fire-box, and the cold air going through these holes has the same effect.
After finishing at night, don't draw the fire, but close the damper and fire-door, and let the Ere die out ; be sure, however, that there is not enough fuel on to make steam and to cause blowing-off, and also take care to leave the glass full of water. By this means the cooling will be more gradual, without setting up any undue strains, and the water will be quite warm in the morning—a great help, sometimes. In the event of SHORTNESS OF WATER ON THE ROAD, don't draw the fire : the best thing to do is to smother the fire, after closing the damper, with dirt or ashes, or with coal if nothing else is at hand, as more than one fusible plug has been melted out which could have been saved had the fire been smothered instead of drawn, and this method also prevents the cold air's rushing through and setting up the severe strains named above. The introduction of large quantities of cold water into theboiler sets up strains in the same way, and this is where an independent steam pump scores over an injector : the steam pump enables a man to feed the water in, evenly and regularly, by varying the speed of the pump, or by controlling the by-pass, independently of the speed of the wagon.
The greatest evil to be contended with is scale and internal corrosion, and this has occupied the minds of chemists and engineers for years. Many are the devices for overcoming this trouble. There are several water-softening plants on the market, but they are, principally, designed to deal with larger quantities of water than are required for steam wagons, so that resource has to be had to boiler fluids, of which there are a large number, and all of which claim special advantages. After trying two or three different kinds,. I have arrived at the conclusion that soda is the simplest and cheapest after all. The principal scale-forming matters in water are the carbonates and sulphates of lime and magnesia, carbonate of lime being mostly found, and thick scale, composed principally of this, will cause overheating of the plates, besides wasting the fuel, owing to its lack of conducting properties. Pitting and grooving are principally due to galvanic action, but, in the case of steam wagons taking up different kinds of water on the road, it is a prevalent idea that one neutralises the effects of another. If a lot of main water from one supply is used, it is advisable to SEND A SAMPLE TO A CHEMIST and to have it analysed, and to act on his advice as to the best course to pursue in treating the water. The method which the writer adopts, once a week, is to mix up a handful of pure caustic soda in a bucket of boiling water, and, by leaving the filling-up plugs off until the fires are alight, and the water in the boilers quite warm, to pour in the solution. The question of feed-water control has previously been dealt with in the pages of " THE COMMERCIAL Mama," and the writer strongly advises any man interested in steam wagons to study those articles carefully. (Vol. 1, Nos. Ie., m, and 14.) In washing out the boilers, which should be done at least once a week, it is necessary to have a good pressure of water on the hose, and to direct a good stream of water all round the fire-box, especially in the corners with locomotive-type boilers. I lave the wagon standing high in the front, when it has a horizontal boiler, as that will allow the mud to settle down round the bottom of the firebox, and to be easily flushed through the hand-holes. Don't be afraid to use plenty of water, and the mud rake, and finish off with a long-handled wire brush with good stiff bristles. In sweeping the tubes of smoke-tube boilers, after removing the scot with the flue brush, have a stiff wire-bristle brush, which is a good fit in the tubes, and work this up and down each tube several times : this will remove a lot of hard adhesions that the ordinary brush will not loosen. With some kinds of coal it mav he necessary to sweep the tubes twice a day; hut, as a general rule, it is sufficient to do this when starting away in the morning. Raise steam slowly, so that the expansion of the boiler is even and regular, and du not put the blower on as soon as you have a few pounds of pressure. Many drivers are in the habit of using the blower unnecessarily ; this is bad for the tubes, and, at the same time, conduces to a heavy coal ox-coke bill. If the boiler is kept properly clean, and the stoker knows his work, that is to say he only puts on fuel in small quantities, it should be unnecessary to use it at ail.