DEFINITIONS FOR TYPES OF BOILERS The following definitions should be remembered in connection with the terms used in designating the various classes.
A boiler is one having the heating surface composed largely of tubes which are surrounded with water, the hot gases passing through them.
A boiler is also composed of tubes, but in this case water flows through the tubes, while the hot gases pass around and among them.
In a sectional boiler the tubes and corresponding headers form comparatively small units. Each unit is complete in itself; that is, it is in communication with a steam and water drum but is independent of the other units.
A boiler is one having all the tubes in communication with one another; in other words, all or nearly all the tubes are expanded into a common header or drum. The boiler is not made up of units.
A boiler is made up of plain tubes.
A boiler has a small tube inside of the regular tube and concentric with it.
A boiler is when the furnace is separate from the shell; in such boilers the fire is usually placed in a brick furnace.
In the boiler the grate is inside of a flue which is within the shell.
A boiler is one having the fire within a fire box which, although external to the shell, is rigidly connected to it. The fire box is usually made of steel plates instead of brick as in the case of the externally-fired boiler.