Double boiler

“ Almost the only danger from explosion of a boiler is from not having sufficient water in the boiler. The boiler is filled in the first place, as has already been explained, by hand through a funnel at the filler plug, or by a force pump. The water should stand an inch and a half in the glass of the water gauge before the fire is started. It should be heated up slowly so as not to strain the boiler or connections. When the steam pressure as shown by the steam gauge is ten or fifteen pounds, the blower may be used to increase the draft. ”

“ It is fortunate, however, that the error is usually upon the safe side of indicating more than the actual pressure.
Any boiler that has been standing idle for a few weeks or months is a dangerous thing to enter, and no one should attempt it until it has been thoroughly ventilated by taking off all the man hole and hand-hole plates and throwing water into it. This is due to the presence of a gas which is generated from the refuse and mud, or scale, which, to a greater or less degree, remains in all boilers. Contact with fire is certain to result in an explosion. ”

“ Amongst the essentials are a receptacle capable of containing the water and the steam produced by its evaporation, and strong enough continuously to withstand with safety the highest pressure of steam for which the boiler is intended. Another essential is a furnace for burning the fuel, and a further one is the provision of a sufficiency of heating surface for the transmission of the heat produced by the combustion of the fuel to the water which is required to be evaporated. ”

“ A pipe C is used for heating the liquor by means of waste steam at the commencement of the operation. The grass is fed into the boiler at the opening D. At E E are gauges for showing the height of the liquor in the boiler, F F F are pipes for the supply of steam, strong ley, and water, and the door G is for the discharge of the boiled grass. Each boiler is capable of holding 3 tons of esparto, and the boiling is completed in about two and a half hours, at [46] a pressure of from 35 to 40 lbs. per square inch. It is said that the boiler effects a saving both in time and the amount of soda used. ”

“ The boilers are upright cylinders, about 5 feet in diameter and 16 feet high, with semi-spherical ends, provided inside with straight perforated diaphragms, between which the chips from one cord of wood are confined. A solution of caustic soda, at 12° B., is introduced with the chips, and fires are started in a furnace underneath. At other works the boilers are heated by steam circulating through a jacket which covers the bottom and sides of the 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. ”

“ Steam pressure may be guarded against by a safety valve; but as this may become set fast in a little time, it would be far better to avoid all chance of steam accumulation by such an arrangement as that shown in Fig. 55, where the circulating boiler is placed within an open-topped boiler behind the kitchen fire, and only receives its heat through the hot water surrounding it, and therefore cannot itself become sufficiently hot to generate steam. ”

“ My experiments however, have developed the fact that, by attaching a tube or box-door to the furnaces of that class of boilers, known as return-flue boilers, in which the chimney or stack is constructed directly above the furnace, and the heat and products of combustion from the furnace are carried along under the boiler and then returned back to the stack through flues or tubes leading through the length of the boiler, the combustion will be so complete that no sparks, and but very little smoke, will escape from obviated ”

“ The boiler is so set that the back of it and all the connecting pipes are inside of the house, only the fire and ash pit doors project through the brick partition into the boiler pit. Much heat is generally wasted from hot water boilers by the direct connection of the chimney with the outer air, that might be saved by means of a well constructed flue. It will be seen that the smoke from the boiler is carried under the tank, in this instance through 8 inch vitrified drain pipe. To prevent the cracking of the pipe near the boiler the first 6 or 8 feet is laid with cast iron pipe. ”

“ To fill the boiler to three gauges and then shut off the feed until the water level is again down, the exhaust steam, after it has heated the water standing in heater, passes off without leaving any of its heat, and then turning on the feed water again much faster than needed, the water has not time to take up so much heat as if the feed were slow and regular. Much bad effect on the boiler is due to the difference in temperature at the time when the feed is off and on.
Never calk a boiler under steam pressure unless you are tired of life. ”

“ The gases available for this class of work are almost invariably very dirty. It is essential for the successful operation of waste-heat boilers that ample provision be made for cleaning by the installation of access doors through which all parts of the setting may be reached. In many instances, such as waste-heat boilers set in connection with cement kilns, settling chambers are provided for the dust before the gases reach the boiler. ”

“ Nearly all foreign matter held in solution in water, on first becoming separated by boiling, rises to the top in the form of what is commonly called scum, in which condition much of it may be removed by the surface blow-off. If not removed, however, the heavier particles will be attracted to each other until they have become sufficiently dense to fall to the bottom, where they will be deposited in the form of scale, covering the whole internal surface of the boiler below the water line, with a more or less perfect non-conductor of heat. ”

“ The injector is not an economical device, but it is simple and convenient, it occupies but a small amount of space, is not expensive and is free from severe strains on its durability; moreover, where a number of boilers are used in one establishment, it is very convenient to have the feeding arrangements separate, so that each boiler is a complete generating system in itself and independent of its neighbors. ”

“ When starting fires close the gauge cocks and safety valve as soon as steam begins to form.
Go slow. It is necessary to start all new boilers very slowly. The change from hot to cold is an immense one in its effects on the contraction and expansion of the boiler, the change of dimension by expansion is a force of the greatest magnitude and cannot be over-estimated. ”

“ Arrangement must prevent all accidental dumpings of fuel in fire pot. Coal so used as to not disappear through grate. One [318] boiler employs a damper rod running to the front which enables the caretaker to open and close the smoke damper rapidly when building and this prevents gas and smoke leakage when door is open. Such a device as this makes a floor room in a cellar feasible. The boilers of some companies are so beautifully contrived and finished that they are no worse than a talking machine or upright piano in a play room. ”

“ 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. ”

“ Notwithstanding all the attempts that have been made, the use of a lead-lined boiler is a serious objection, and any process which will fulfil the conditions on which the bi-sulphite processes depend, and which at the same time admits of the use of the ordinary iron boilers, is an obvious desideratum. ”

“ As the flat ends of such boilers are always being sprung by each alternation of pressure into a more or less spherical shape, as shown by the elastic model exhibited, this consideration no doubt led to the ends being made hemispherical, as shown in Pg 21 Fig. 25; and plain cylindrical boilers with these hemispherical ends are now so commonly used that they far outnumber any other form of boiler. Their shape renders them very strong, as the whole of the iron is in simple tension, and internal pressure has no tendency to alter the shape, as is shown by the elastic model exhibited. ”

“ In guarding against explosion it is conceded that the main reliance is to have the boiler made strong enough to stand both the regular load or any unexpected strain caused by the stoppage of the engine; it is also the tendency of the times to proceed towards higher and higher figures in steam pressure, until now it is not unfrequent to see 150 lbs. to the square inch indicated by the gauge; the larger the boiler, also, the more economically it can be run and this, as in the two cases before cited, requires extra precautions in building the boiler with great regard to strength in every part. ”

“ One or two cross-tubes generally suffice to convert a useless boiler, that is, one that will not generate enough steam, into an effective one.
The fuel used to heat small boilers is generally spirits of wine. This is put in a suitable receptacle and burnt through a cotton wick. Several wicks are used in large boilers, and they are placed to heat the largest surface available. Spirit lamps are a source of danger if proper precautions are not taken. Unless there is a free outlet for the air within the lamp, it will be expanded by the heat and cause the spirit to rise too quickly in the wick. ”

“ A hard scale is equivalent to thickening the plate; and although this is sufficiently mischievous, the injury to the plates is much more rapid when a thicker but spongy deposit entirely prevents contact of the water and impedes the transmission of the heat. An attempt to illustrate this is given in Fig. 58, which is an enlarged view of a portion of such a boiler as is shown in Fig. 37. Pg 87 The money spent in boiler compositions would be better applied in securing a supply of proper water, or in filtering and purifying the water before it enters the boiler. ”

“ In order to burn the finer grades of anthracite coal in sufficient quantities to obtain boiler rating with the hand-fired grates, and in order to secure a large excess over boiler rating with other coals, a system of blowers and air ducts has been provided in the basement under the boilers. One blower is selected for every three boilers, with arrangements for supplying all six boilers from one blower. ”

“ 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. ”

“ 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. ”

“ Always purchase a boiler with sufficient capacity to allow a small margin beyond its ordinary requirements. Be sure and have the boiler or boilers properly set so that the best results may be derived from the fuel burned. Many good boilers are condemned because they do not steam well on account of bad setting.
If a locomotive style of boiler, see that it has a large fire box (well stayed) and a sufficient number of flues to allow of easy firing and good combustion of the fuel without being obliged to use a forced draft. ”

“ Being of a spherical form, it is twice as strong as a cylindrical boiler of the same diameter and thickness. The plates used are, notwithstanding, of the usual substance, thus rendering it perfectly safe, durable, and suitable for high-pressure steam. The spherical shape also allows the rags to fall out by themselves when the boiler is revolving with the cover off. Within the boiler are strainers to carry off the dirt, and lifters to agitate the rags during the process of either boiling or washing. ”

“ Every part of the boiler being cylindrical, it has the form which, mechanically considered, is most favourable to strength, and which, within given dimensions, contains the greatest quantity of water. It is also free from the defects arising from unequal expansion, which are found to be most injurious in tubular boilers. The tubes C and K can freely expand in the direction of their length, without being loosened at their joints, and without straining any part of the apparatus; the tubes E, being short, are subject to a very slight degree of expansion ”