Water-tube boiler

“ The feed water usually enters the upper or steam drum and is conducted by down tubes to a lower or water drum; from here the water, becoming heated, rises and passes up through steam-collecting tubes to the steam drum. Thus a circulation is set up. The efficiency of a water-tube boiler depends in a large measure on proper circulation. As the distance of grate to smoke stack is rather short, most types of water-tube boilers have a system of baffle plates for conducting the gases among the tubes to increase the distance of travel. The economy depends in large measure on efficient baffling. ”

“ Like all water-tube boilers, they require to be frequently cleaned if impure feed-water is used, but the straightness of their tubes enables their condition to be ascertained at any time when the boiler is out of use, and any accumulation of scale to be removed. The super heaters, which are frequently fitted, consist of two cross-boxes or headers placed transversely under the cylindrical drum and connected by numerous ⊂ shaped tubes. They are situated between the tubes and the steam-chest, and are exposed to the heat of the furnace gases after their first passage across the tubes. ”

“ In any case, neither is likely to oust existing types, as most of the valuable points in a boiler are already patented all over the world. The inventors of new types are, therefore, hampered much like inventors of new systems of wireless telegraphy are—some one has been before them. In addition, a water-tube boiler requires some years of practical service before it can be classed as out of the experimental stage. The great advantage possessed by the Belleville, which “in theory” is one of the worst of boilers, lies in the numerous features introduced by years of practical experience. ”

“ In the case of a rupture in a water-tube boiler, the loss will ordinarily be limited to one or two tubes which can be readily replaced. The fire-tube boiler will be so completely demolished that the question of repairs will be shifted from the boiler to the surrounding property, the damage to which will usually exceed many times the cost of a boiler of a type which would have eliminated the possibility of a disastrous explosion. ”

“ The Scotch Marine type of boiler used on steam ships, has slightly more grate area and slightly less heating surface than the locomotive type of boiler, because the rate of combustion is lower. Stationary water-tube boilers may have 2 to 3 times as much grate area and heating surface per 150horse-power as is found in locomotive boilers. If a poor type of fuel is to be used the area of the grate should be increased about inversely as the heat content of the fuel. ”

“ A modern, highly efficient and economical steam driven high speed compressor plant must be installed so as to get the maximum power out of coal. The boiler room will contain two 250-H. P. water-tube boilers with automatic stokers and coal bin overhead holding two weeks' supply of coal. Steam pressure 175 lbs. As the firing of the boilers is automatic and requires practically no work on the part of the engineers, no firemen are needed. ”

“ When we come to construction of the boiler plant on expensive city property, where we are cramped for space, we are almost limited at once to some one of the types of sectional water-tube boilers. In the Brooklyn station we are practically limited to the consideration of this class, and have not only 125nbsp;pounds but 150 pounds boiler pressure, and even higher. We have also the advantage of quick steaming under heavy changes in load. ”

“ A boiler of this kind is illustrated in fig. 4. This form is often used on board ship for auxiliary purposes. Where more heating surface is required than can be obtained in the cross-tube boiler other types of vertical boiler are employed. For instance, in the “Tyne” boiler (fig. 5) the furnace is hemispherical, and the products of combustion are led into an upper combustion chamber traversed by four or more inclined water-tubes of about 9 in. diameter and by several vertical water-tubes of less diameter. ”

“ The boiler is connected by a tube with a large stationary boiler in the cellar beneath, and a constant supply of hot water passes from the latter to the former. This tube being automatically severed from the engine the instant an alarm is sounded, and the engine-fire kindled at the same moment, a sufficient pressure of steam for the pumps is generated long before the scene of the fire is reached, and so again valuable time is saved. ”

“ It has many decided advantages, but is costly to make. The formation of the two ends into separate fire-boxes leaves the bottom of the boiler free to adapt itself to the variations of temperature to which it is exposed. The separation of the furnaces from the combustion chamber, excepting through the opening afforded by a connecting tube, is an advantage in the same direction, and avoids almost entirely the racking strains due to irregular furnace action. The weight of water carried is less, and that of the boiler may also be made less ”

“ The largest size of single-ended large tube boiler in use has a steam drum 4 ft. 2 in. diameter, a grate area of 73.5 sq. ft. and 3750 sq. ft. of heating surface, but much larger double-ended boilers have been made, these being fired from both ends.
In most of the boilers made, access to the inside is obtained by manholes in the steam-chest and water-chamber ends, but in the smaller sizes fitted in torpedo boats the water-chambers are too small for this, and they are each arranged in two parts connected by a bolted joint, which makes all the tube ends accessible. ”

“ They are rarely made with bottoms, or with stuffing boxes, and are consequently, for the most part, adorned with stalactites of salt after a short period of service. The water discharged from them, too, from the want of a proper conduit, disfigures the front of the boiler, and adds to the corrosion in the ash pits. It would be preferable to combine the gauge cocks appertaining to each boiler into a single upright tube, connected suitably with the boiler, and the water flowing from them could be directed downward into a funnel tube communicating with the bilge. ”

“ The boilers are designed for a working steam pressure of 225 pounds per square inch and for a hydraulic test pressure of 300 pounds per square inch. Each boiler is provided with twenty-one vertical water tube sections, and each section is fourteen tubes high. The tubes are of lap welded, charcoal iron, 4 inches in diameter and 18 feet long. The drums are 42 inches in diameter and 23 feet and 10 inches long. All parts are of open-hearth steel ”

“ A class of water-tube boilers largely in use in torpedo-boat destroyers and cruisers, where the maximum of power is required in proportion to the total weight of the installation, is generally known as express boilers. ”

“ It is automatically taken care of where the house is heated by an oil burning system. With a coal burning steam or hot water plant, there is now a cylinder that can be attached to the boiler below the water level. In it there is a coil of copper pipe through which circulates the domestic hot water supply. This works admirably. There is always a sufficient supply but it is never so overheated as to scald the heedless person who plunges a hand under a boiling stream of water. ”

“ It must be remembered that dry steam, as it is used through the engine or for other purposes, carries away none of the impurities which pass with the water into the boiler; hence, in a battery of boilers burning, say, 20 tons of coal per day and evaporating 10 lbs. of water to a pound of coal, there is a body of water going through them every day of 200 tons. Multiply this by 300 days for a year = 60,000 tons, and it will be seen how very great is the problem of keeping the interior of the boilers free from scale and deposit. ”

“ Of course this adds a great deal to the work, but it means safety, for when the boiler is kept well filled it cannot burst, neither can pipes freeze if there be no water in them to bring about this very disagreeable state of things. A low-pressure boiler having a lid that comes off, can always be hand-filled easily, while cans of water must be placed wherever one is accustomed to use water freely; and though baths may be curtailed and work increased, no damage or danger can ensue. ”

“ The boiler, minus the water and boiler-head perhaps, goes through ceiling, roof, and brick walls, as if they were cobwebs, and, surrounded with fragments of men and things, is seen descending like a comet through the neighboring air.
To get rid of this liability to have a Thor-hammer or thunderbolt generated in the stomach of a steam-engine, at any moment when the vigilance of the engineer happens to be at fault, something is going to be done. No safety-valve or fusible plug is adequate. The boiler cannot be all safety-valve. ”

“ Although the best types of fire engine boilers require but a few minutes’ time to generate a working pressure from cold water, the general adoption of many improvements has made the stationary heater an essential part of a complete equipment.
Experience proves that the life of the boiler is prolonged by being kept constantly in a state of activity, and the elevated temperature of the water insures prompt and efficient work by the steamer at the very time when a few moments’ delay may breed disaster. ”

“ It is better to let nature take its course, to a certain extent, and neutralize what little mineral deposit forms in the boilers with as small an amount of vegetable matter as possible.
It is well to note that different waters require different treatment; what will be of benefit in one instance will be of no value whatever in a different water, many of the “compounds” sold to prevent and remove scale will certainly destroy a boiler if they are used persistently, because they are composed of the exact opposite chemicals which should be used ”

“ No well-informed proprietor suffers his boiler to be without one; but it is not a cure for carelessness. It is only a window for the vigilant eye to look through, not the eye itself. Steam-boilers will have to be constructed so that when the subsidence of the water fails to check itself by enlarging the supply, it shall, before the point of danger is reached, infallibly check the combustion, let off the steam, and blow a whistle or ring a bell, which the proprietor may, if he pleases, regard as the official death-knell of the careless engineer. ”

“ It has taken considerable time for the belief in the weakness of large tubes when exposed to external pressure to become general, and a great many boilers are still made and used having even large tubes without the strengthening rings; and in some districts such boilers are used in great numbers and at far higher pressures than can be considered judicious. In more than one bed of boilers, one boiler after another has exploded by the collapse of the tube from the want of strengthening rings, and yet these have still been believed unnecessary ”

“ It is necessary that in each individual plant there be a basis on which to judge the cleanliness of a boiler. From the operative’s standpoint, it is probably more necessary that there be a thorough understanding of the relation between scale and tube difficulties than between scale and efficiency. It is, of course, impossible to keep boilers absolutely free from scale at all times, but experience in each individual plant determines the limit to which scale can be allowed to form before tube difficulties will begin or a perceptible falling off in efficiency will take place. ”

“ All the inside and outside surfaces should be kept clean to avoid waste of fuel; to aid in this service the best forms are provided with extra facilities for cleaning. For inspection, remove the hand holes at both ends of the tubes, and by holding a lamp at one end and looking in at the other the condition of the surface can be freely seen. Push the scraper through the tube to remove sediment, or if the scale is hard, use the chipping scraper made for that purpose.
Hand holes should be frequently removed and surfaces examined, particularly in case of a new boiler. ”

“ This can be best utilized by exhaust feed water heaters, for the use of live steam heaters represents no saving in fuel, as all the heat imparted to the feed water by their use comes directly from the boiler. The purpose for which they are used is to elevate the temperature of the feed water above the boiling point, so as to precipitate the sulphate of lime and other scale forming substances, and prevent them from entering the boiler. Neither does the heat in the feed water introduced by an injector represent saving, as it comes from the boiler and was generated by the fuel. ”

“ This form of boiler is frequently used to good advantage where it is desired to utilize ground space, and where there is sufficient head room. Properly constructed, it is economical as a steam generator.
From the foregoing it will be seen that the structural features of all boilers are so arranged as to provide for the exposure of the largest possible area of water to a heated surface so that the greatest amount of heat from the fuel may be absorbed. ”

“ Cooling towers make it practicable to return all water to the boiler even from non-condensing engines. Then only the waste needs to be made good, and any water can be purified for this purpose. Oil or grease with the feed-water is readily avoided. Only electrolysis remains to be provided against, which can be done by avoiding the use of any alloy of copper in contact with the water. We may then have boilers of the most durable character and safe to carry any desired pressure. ”