Air vessels are used on the delivery side of a pump to cushion the discharge of water and prevent concussion, water being incompressible. They are also sometimes useful on the suction side, where the lift is considerable. A piston and spring may be employed instead of an air vessel. See [No. 2121].
Pumps required to run constantly, but deliver water intermittently only, are worked (a) by an air valve on the suction side which, when open, stops the water suction; (b) by a pass valve between suction and delivery which, when open, passes the delivery into the suction again; and (c) by a waste valve on the delivery.
Section 57.—PIPES AND CONVEYORS.
(See also [p. 128].)
[2338]. Boiler tube, internally ribbed. Serve’s patent.
[2339]. Boiler tube flue, corrugated, to add to its strength and heating surface. Fox’s patent.
[2340]. Pipe joint, with toggle clips.
[2341]. Pipe flange, with caulking groove.
Flexible tubes, metallic, are now manufactured by the Flexible Metallic Tubing Co. in most metals, including steel, and in various strengths and with various degrees of flexibility, from that of plain rubber to such stiffness as requires a little force to bend it. These tubes are perfectly air-tight, and will stand great pressures.