ABSTRACT
In gravity-type variable-area flowmeters, increasing flow lifts the float, piston, or vane, and it is the weight of these flow elements that have to be balanced by the kinetic energy of the flowing stream. All variable-area flowmeters can be provided with direct local indicators. In the discussion below, the different variable-area flowmeters will all be discussed, starting with the tapered tube (rotameter) designs. Rotameters are available which transmit pneumatic, electronic, or time pulse signals, or provide recording, totalizing, or control functions. In some designs the bypass rotameter is provided with a range orifice which is sized to lift the rotameter float to the maximum position when the flow in the main line is the maximum. The tapered-plug variable-area flowmeters are made with metallic meter bodies and are used on higher pressure applications, where errors of 5 to 10% full scale can be tolerated.
