Boiler

A closed vessel in which steam is generated from water. The various kinds of boilers come under the following heads:

Drop Flue Boiler. One in which the course of the gases is direct from the furnace through flues back to a connection, then down, returning towards the front through flues underneath the first series, thence into another connection and down and through a third series of flues to the smoke-box at the back end of boiler.

Fire Tube Boiler. The water circulates about the tubes and the fire through them.

Horizontal Return Tubular, or Flue, Externally Fired. Cylindrical in shape, containing small tubes reaching from end to end. The furnace is directly under the shell, the products of combustion passing along the bottom of shell to back end, thence returning through tubes or flues to the smoke-box.

Horizontal Return Tubular, Internally Fired-"Scotch." Cylindrical in shape, containing one or more cylindrical furnace flues. From the furnace the gases pass back into a connection, thence return through tubes above the furnace to the smoke box on front end.

Horizontal Return Tubular, Double Ended. The same as two single boilers back to back, but enclosed within the same shell.

Lobster Back. One in which the course of the gases is from the furnace into a low connection, and from thence into flues leading forward to another connection, returning over these flues and the furnace through other flues to a front connection, thence back through tubes to a middle connection and up to chimney.

Locomotive. Has an arched, flat-sided part called "wagon-top," containing one flat-sided furnace with arched crown, and built on to the back of it a cylindrical part called the "barrel." The gases pass from the furnace back through small tubes direct to smoke-box at back end.

Return Tubular; Leg; Flue and Return Tubular. Has an arched, flat-sided part called "wagon-top," containing one or more flat-sided furnaces with arched crowns; built on to the back of this is a cylindrical part called the "barrel." The gases pass out of the furnace through flues at the bottom of "barrel" to back connection, thence returning through small tubes over flues and furnaces to the smoke-box at front end.

Upright Tubular. In shape a cylinder set on end. The furnace is at the lower end and the gases pass upward through tubes to the smoke-box at top.

Water Tube Boiler. The water circulates through the tubes, and the fire circulates about the outside.