MECHANICAL BOILER CLEANERS.
Owing to the fact (1) that nearly, if not quite all, the impurities which exist in feed water are set free by a high temperature attained under pressure; (2) that these impurities are left in the boiler by the constant use of the steam, there follows the result that the water remaining is more and more impregnated with the residuum composed of the foreign matters which (the water removed) constitutes mud, scale, etc.
The custom has been and is now to regularly “blow off” one or two gauges of this water once or twice per day replacing it with fresh water of less density; that this is a very imperfect method for removing the foreign matter is readily allowed, besides wasting absolutely all the units of heat contained in the water blown off.
Now, within the boiler while in use, under the operation of the fierce heat of the furnaces, are constant changes in the position of the water caused by the boiling, by the withdrawal of the steam and by the constant effort of the hot water to rise and the cold water to fall. The water thus keeps in circulation everything within the boiler, including the sediment, except in places where the water is from any cause without motion. In these quiet nooks there is a constant depositing of the elsewhere active foreign matters contained in the water, which deposits, in the form of mud and scale, left undisturbed, causes loss and danger.
It is in taking advantage of these facts, and of the principles of the circulation of hot and cold water, that mechanical boiler cleaners are brought into successful use.
These devices for the stilling of the water and collection of the sediment are made in various forms and all sizes and capacities, and are located at the sides or back of the boiler setting and even on top of the boiler. There is a system where pipes in a coil are fixed in the sides of the furnace and exposed to its greatest heat, and which, owing to their enlarged area, act as most efficient reservoirs. In all these devices there is an upflow pipe connected with the lower and coolest water, and a return pipe connecting with the top of the water where it is hottest. This arrangement assures a constant current which is more or less rapid according to the intensity of the fire and which keeps up as long as the firing is done. Where this current passes through the reservoir, the enlarged area and comparative quiet is favorable for the deposit of the sediment and in practical experience it does deposit nearly all of it. The collection of the impurities is helped by a funnel-shaped appliance placed at the opening of the upflow pipe, which, aided by the rapid flow of the hot water, carries the floating scum towards it into the reservoir. Attached to the reservoir is the blow-off pipe through which the deposited matter is removed as often as necessary.
The use of these mechanical cleaners is readily understood: (1) they provide a place of accumulation for the sediment; (2) they save the necessity of opening the boilers to remove by hand, the refuse of the boiler; (3) save fuel by avoiding the necessity of frequent blowing off one or two gauges of water, and (4) by the preventing the formation of scale with its attendant evils.