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the piston has a center vertical pin which is confined to a circular track that is part of the chamber. Differential pressure across the meter causes the piston to sweep the chamber wall in the direction of flow. This oscillating motion displaces liquid from the inlet to the outlet port in a continuous stream. To further prevent unmeasured liquid from passing through the chamber, the piston has a horizontal partition or web. This web is perforated to promote balanced buoyancy of the piston within the chamber and a linear flow pattern of liquid through the meter. A drive bar and shaft are positioned through the top of the chamber so that, as the piston oscillates, the piston pin drives the bar and shaft in a circular or spinning motion. This rotating shaft is the driving link between the piston and the register or readout unit. Sizes range from 0.75 to 2 inches (19 to 51 mm), with capacity ranging from 5 to 150 gal/min (19 to 570 L /min). Fluted Rotor Meter Meters of this type are used in the flow measurement of crude and refined petroleum products and a variety of other commercial fluids. Frequently they are used on product loading racks and small pipelines. Usually the meters are equipped with direct readouts and often with ticket printers to provide authentically recorded documents for liquid-transfer transactions (Fig. 37). Oval-Shaped Gear Flowmeters In these meters, precision-matched oval-shaped gears are used as metering elements (Fig. 38). Meter sizes (connections) range from 1/2 to 1, 11/2, 2, 3 and 4 inches (∼ 1.3 to 2.5, 3.8, 5.1, 7.6, and 10.2 cm), with capacity ranges for different fluids as follows:

FIGURE 37 Operating principle of a Brooks BiRotor possitive-displacement flowmeter. As the product enters the intake of the measuring unit chamber, the two rotors divide the product into precise segments of volume momentarily and then return these segments to the outlet of the measuring unit chamber. During what may be referred to as “liquid transition,” the rotation of the two rotors is directly proportional to the liquid throughput. A gear train, located outside the measuring unit chamber, conveys mechanical rotation of the rotors to a mechanical or electronic register for totalization of liquid throughput. (Brooks Instrument Division, Emerson Electric Company.)

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Mechanical BE (Measurement and Instrumentation)  

Mechanical BE (Measurement and Instrumentation)

Mechanical BE (Measurement and Instrumentation)  

Mechanical BE (Measurement and Instrumentation)

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