Peculiar Forms of Vertical Water-Tube Boilers - Hazelton or Porcupine Water Tubes Horizontal Steam and Water Drum Vertical Straight-Tube Single-Tube

PECULIAR FORMS OF VERTICAL WATER-TUBE BOILERS - HAZELTON OR PORCUPINE: WATER TUBES HORIZONTAL, STEAM AND WATER DRUM VERTICAL, STRAIGHT-TUBE, SINGLE-TUBE The Hazelton water-tube boiler differs in many ways from the boilers thus far described. Like most water-tube boilers it consists of a steam and water drum and water tubes, but the central standpipe is vertical and the short horizontal tubes radiate from the central drum. According to our classification it is not a vertical water-tube boiler because the tubes are horizontal, also, it is not a horizontal boiler as in general appearance it is vertical.

The grate is. circular and formed around the central drum which rests on a circular cast-iron foundation. Above the grate, the central drum forms part of the heating surface and is the steam reservoir; below the grate it is the mud drum, which may be entered by means of a manhole just below the grate. As shown in Fig. 66, the standpipe above the fire is provided with radial tubes. The appearance of these tubes gives the name "porcupine".

The standpipe is about three feet in diameter for large boilers. The tubes are about four inches in diameter, and two and one-half feet long, the number varying with the capacity of the boiler. The outer ends of the tubes are closed and hemispherical, and the inner ends expanded into the standpipe. These tubes are free to expand and contract without bringing any strain on the boiler.

Steam is taken from the top of the central drum. To get dry steam, small pipes are inserted as shown in Fig. 67. The steam passes up into the small tube at the top of the standpipe and then through the small pipes to the ends of the generating tubes. It then flows back through the generating tubes to the annular space and from thence to the steam pipe. The feed pipe enters the mud drum and extends upward nearly to the water line; it then returns nearly to the level of the grate, terminating in a spraying nozzle. This type of boiler may be enclosed in a brick setting as shown in Fig. 66 or by a sheet steel covering lined with fire brick.