CARBONATE Of principal substance which causes the incrustation of steam boilers and water-pipes. It is held in solution in the water as a bicarbonate by the excess of carbonic acid. When the boiler is heated the excess of acid is driven off, and the carbonate is precipitated in the form of a muddy deposit which hardens in the presence of heat into the form of an injurious scale.
The of burring or up the edges of boiler platesalong the riveted seams to make e them steam and water tight. The caulking of the joints between boiler shells and the flanges of cast-iron man-holes. and safety and stop valve seatings. is accomplished by means of caulking-strips orstrips of sheet metal interposed between the wrought-iron of the shells and the cast-iron of the pieces attached thereto. This is rendered necessary on account of the impossibility of ca • the cast-iron. The tube or funnel through w the waste steam and smoke escapes from an engine or boiler into the open air. Its proportions bear a definite relation to the grate area, and vary in the different types of engines. Criecuternec Twins.— The cross tubes of vertical boilers, or the ordinary forms of tubes used in multi-tubular boilers or surface condensers.
The circulation in a steam boiler is caused by the bubbling up of the lighter boiling water from the heating surfaces through the heavier cooler water in the portions which descends and thus comes in contact with the heating surfaces. Efficient circulation
is necessary to the rapid generation of steam, and for the prevention of incrustation. It is promoted by the use of properly arranged water tubes.
The removal of the clinkers or other vitrified material from the fire in the boiler, periodically. CLorgueu.— The jacketing or deadening covering placed around boilers to prevent loss of beat by radiation. Non-condu cting compositions of felt, silicate cotton, asbestos. etc., which are smeared or placed around steam boilers while the substances are in a plastic state, and which become subsequently hardened by the heat, and prevent the loss of heat from the boiler by radiation. COLD WATER hydraulic test, for pressure only, applied to steam boilers, as distinguished from the hot water test.
The destruction of the tubes and fire-boxes of steam boilers by external pressures, which cause them to fail by bending or, crumpling inwardly.
Cou-gcroa.— A cylindrical vessel enclosed in a steam boiler for the purpose of collecting the sedimentary matter contained in the water, which if allowed to remain in the water would produce injurious scale and incrustation. The material thus collected is removed by being blown-out at intervals.