GB1420754A - Flowmeter calibration or proving apparatus - Google Patents

Abstract

1420754 Measuring fluid-flow INDUSTRY SECRETARY OF STATE FOR 8 May 1973 [8 May 1972] 21349/72 Heading G1R In a flowmeter calibrating apparatus including an elongate tube 1 containing a displacement member 3 whose displacement between fixed locations along the length of the tube into the fluidflow is timed, the member 3 has at least two longitudinally spaced sealing members 4, 5 with a cavity 6 formed between them such that any fluid leaking past the sealing members is trapped in the cavity whence it can be removed at a valved tapping 16b and measured and the flow-rate measurement appropriately connected. The same, or a further, tapping (16a), 16b may be used to evacuate air from the cavity 6, the tube 1 preferably being inclined at 2 degrees to the horizontal to facilitate removal of air and the fluid from the cavity. Each end of the tube 1 may be, as in Fig. 4 (not shown) equipped with temperature and pressure transmitters, and also, Fig. 5 (not shown) with hydraulic accumulators to absorb the kinetic energy of the member 3 at the end of its travel should an automatically-actuated control valve system fail to stop it. Optical sensors (15a-15f) responsive to the passage of the member 3 may be spaced along the tube 1, the member 3 having an annular mirror 25 with a surface 30 to reflect a light beam 34, e.g. from a He/Ne laser, directed through a window 32 in the tube, part of the reflected beam being deviated by a beam-splitting prism 35 on to a lightsensitive switch 39. In an alternative embodiment, Figs. 6 and 7, (not shown), in addition to an optical sensing arrangement, an independent magnetic sensing arrangement is provided, the member 3 having an annular polepiece (64) and magnets (67), (68) whose passage is sensed by magnetically-sensitive diodes (70) fixed in the tube wall. Preferably the diodes (70) are connected in matched pairs in thermal contact and in magnetic opposition, the voltage at a point between the pair being compared with a reference voltage in a trigger circuit as in Fig. 8 (not shown). Alternatively the apparatus may have mechanical or ultrasonic sensing arrangements.