Horizontal Water-Tube Boilers - Babcock and Wilcox Water Tubes Nearly Horizontal Steam and Water Drum Horizontal Straight-Tube Single-Tube Sectional

HORIZONTAL WATER-TUBE BOILERS - BABCOCK AND WILCOX: WATER TUBES NEARLY HORIZONTAL, STEAM AND WATER DRUM HORIZONTAL, STRAIGHT-TUBE, SINGLE-TUBE, SECTIONAL Construction. This boiler consists of a large number of lap. welded, wrought-iron, 4-inch tubes connected to each other and to a horizontal steam and water drum. The arrangement of the parts is shown in Fig. 41 which is a side view of a much-used form of this boiler. Each tube is expanded into a forging of the form shown in Fig. 42.

The tubes in a vertical row enter one piece and this vertical row is independent of the others, as shown in Fig. 43. Thus it is readily seen that this is a sectional boiler. Fig. 43 shows also the " staggered " arrangement of the tubes. In the back side of the front header, and in the front side of the rear header, holes are drilled into which are expanded the water tubes. In the front side of the header a flanged hole opposite each tube is fitted with a hand-hole plate. The details of construction are shown in Fig. 44. The tops of the headers are con nected to the steam and water drum by short tubes and the same construction is used for connecting the mud drum to the rear header.

Operation.

The grate is at the front end of the boiler under the higher end of the tubes. The hot gases from the fire are guided division plates and bridges, so that after rising from the grate they pass between the tubes to the combustion chamber, which is under the steam and water drum; the gases then pass downward among the tubes, and after rising a second time pass off to the chimney. In this way, the direction of the currents of hot gases is at all times almost at right angles to the tubes, thus impinging upon them instead of passing parallel to the heating surfaces, as in the case of fire tubes. As the gases impinge three times against the staggered tubes, the heating surface is very efficient.

Circulation.

The feed water enters the steam and water drum through the pipe shown in Fig. 44. It is thus heated before it mixes with the hot water in the boiler. As the water in the tubes becomes heated, it rises to the higher end where it is partly converted into steam; a column of water and steam rises through the header to the drum in which the steam and water become separated. The cooler water at the rear of the steam and water drum flows down into the lower end of the tubes and as it becomes heated rises. Thus there is a continuous circulation.

Steam is taken from the rear end of the steam and water drum. The solid matter in the water is not deposited on the tubes because of the rapid circulation; it falls to the mud drum from which it is blown out.

The marine form of this boiler has a cross drum, that is, the drum is at right angles to the tubes instead of parallel to them. It is similar in form to the cross-drum types used for stationary work. This form is used in case there is not sufficient head room.