Rotary valves are those in which the disc, or plug, or other device used to close the passage, is made to revolve for opening or closing, the common stop cock being an illustration.
Lifting valves are those in which the full cone or stopper is lifted from the valve seat by pressure from below, the poppet, and safety valves being examples.
Pressure regulator valve—this is sometimes called a reducing valve and is illustrated in Figs. [142], [143], on page 262. It is designed to reduce the pressure from a high point in the boiler to a lower one in a system of piping, etc.
Usually the smaller valves, not exceeding 11⁄4 inch in diameter, are wholly of gun-metal; the larger are commonly made with cast-iron bodies and gun-metal fittings. The smallest valves, from 1⁄4 up to 1⁄2 inch inclusive, have the disk solid with the spindle, and have an ordinary stuffing-box with external gland. Valves of 3⁄4 inch and upwards have the disk loose from the spindle; up to 3 inch valves the spindles are screwed to work inside the casing; above that size the screwed portion is outside the casing. Above the 3-inch size the nozzles of the cast-iron bodies are generally flanged instead of tapped.
STEAM FITTINGS.
A few of the principal sorts have been illustrated in this work and still others will be described in the [“Index”] at the close of the work.
[Fig. 123], page 251, illustrates an elbow with outlet. This is sometimes spelled with the capital L, and again as an ell.
[Fig. 124] shows a long nipple.
[Fig. 125], page 253, exhibits a bushing, used to reduce one size pipe in a line to another.