GB981334A - Improvements in or relating to arrangements for controlling and/or metering the flow of a liquid - Google Patents

Abstract

981,334. Liquid flowmeters. SANGAMO WESTON Ltd. May 24, 1961 [May 25, 1960], No. 18513/60. Heading G1R. An arrangement for controlling and/or metering liquid flow comprises a downward flow-pipe 19 having means 20 between its ends for indicating or sensing the position of the top 33 of a column of liquid therein, a discharge control valve 25 or jet in the lower end of the flow path 24 from the flow pipe 19, jet or other flow restriction 13 in the liquid supply path 15 to the flow pipe, one of the said jets &c., being of precisely known flow characteristics and at least one jet &c., being variable to adjust the flow to a vlaue at which the restricted liquid input to the flow-pipe 19 is just sufficient to maintain a column of liquid in the flow tube at a given datum level 33. A pump 31 raises liquid from a sump 29 to a tank 10 whence it flows by way of a float chamber 12 (float not shown) for providing a head of liquid nl to a jet 13 which is to be calibrated in a pipe 15 shaped to avoid airlocks, and thence to a constant level weir 17 in a level tank 16 leading into the inlet pipe 19. A closed chamber 21 at the box of the pipe 19 is provided with a cock 22 and vent pipe 23 for bleeding off trapped air. The means 25 is a variable jet whose flow characteristics are precisely known and which opens into a constant level tank 26 with a weir 27 whose distance n2 below the indicator 20 defines the liquid level 33. By manipulating the variable jet 25 inlet the lever 33 is constant the rate of flow through the jet 13 may be determined. In a form of the apparatus shown in Fig. 2 the chamber 21 is omitted and the height of the liquid at the indicator 20 is detected at 35 by photo-electric, electrical-resistance or other means. A signal so obtained is amplified at 36 to operate a servomotor 37 which may either vary the jet 25a to match flow from the jet 13a as a monitoring device as in Fig. 2 or control flow through a variable jet at 13a to match a predetermined setting of a variable jet at 25a (Fig. 3 not shown). Means may also be included for varying the datum level 33 to compensate for changes in temperature or viscosity of the liquid. In a pressurized system back-pressure of air or gas may be provided in the chambers at 10, 12, 16, 26 and 29.