GB1398957A - Liquid storage tanks - Google Patents

Abstract

1398957 Measuring fluid flow LINDE AG 9 March 1973 [17 March 1972] 11633/73 Heading G1N The flow-rate of a liquid passing through a discharge line from a storage tank is determined by timing the fall in level of the liquid between the plates of a capacitor at least partially immersed in the liquid. A liquefied gas tank 1,2 has disposed therein a cylindrical capacitor including, as one electrode, the outer cylindrical casing 10 and as the other electrode a central core, Fig. 2 (not shown). Liquefied gas normally flows through lines 3,4 into the tank, collects there and is withdrawn through lines 5,6,7 discharge valve 8 being set to connect lines 5 and 6 and a permanently constant liquid level C being maintained using a level indicator 20 controlling valve 21. At the same time a valve 13 is opened so that the annular space between the electrodes of the capacitor is filled with the liquid to the level C. To measure the flow-rate through line 6 valve 8 is set to connect line 11 to the line 6 and close line 5. Liquid thus flows out of the annular space in the capacitor into line 6 and the capacitance changes as the liquid falls. When the level reaches a switching point 18 a timer 19 is set into operation and is switched off again when the level passes switching point 14. At the same time valves 8 and 13 are restored to their original states. Since the volume of the annular space between the capacitor electrodes between points 18 and 14 is known and the time taken to pass these points is taken the flowrate can be determined. Capacitor construction Within the annular space of the capacitor horizontal discs are provided arranged vertically one above the other at points corresponding to the switching points 14-18. The radius of each disc is only slightly less than the inner radius of the outer casing 10 so that relatively large changes of capacitance occur over short time periods at these points to generate an electrical signal.