Diagram of a superheater

Figure 4-7.—Diagram of a superheater. one type of boiler to another and from one boiler manufacturer to another. Figure 4-6 shows the arrangement of the steam drum internal fittings in a single-furnace boiler. . The feedwater pipe receives feedwater from the economizer and distributes it throughout the length of the steam drum. . The chemical feed pipe is used to inject chemicals into the boiler to maintain the proper pH and phosphate balance in the boiler water. l The surface blow pipe is used to remove suspended solid matter that floats on top of the water and to lower the steam drum water level, when necessary. The surface blow pipe is also used to blow water out to lower the chemical level in the boiler when it becomes too high. . The dry pipe is used to direct the steam to the steam drum outlet nozzle after it leaves the scrubbers. . The vortex eliminators are used to reduce the swirling motion of the water as it enters the downcomers. l The baffle plates are used to direct the steam to the steam separators. l The cyclone steam separators remove moisture from the steam. This is accomplished by the steam spinning or changing direction. The water drains back into the steam drum while the steam continues upward through a screen and scrubber that removes still more moisture. After the steam leaves the scrubbers, it goes to the dry pipe (fig. 4-6). From there it leaves the steam drum through the steam drum outlet. Figure 4-7, view A, shows the steam going to the inlet header of the superheater and passing through the U-shaped tubes of the superheater to the next header (fig. 4-7, view B). This header is called the first pass or intermediate header. Steam may pass through the U-shaped tubes several times before passing to the outlet header. Each time the steam goes from one header to the next header it is called a pass. The number of passes the steam makes in a superheater varies with different boilers and the degree of superheat that is required for a particular ship. 4-9