GB1319325A - Flow metering devices of the pressure differential producing type - Google Patents

Abstract

1319325 Construction of differential pressure flow meter tubes GENERAL SIGNAL CORP 3 Nov 1970 [3 Nov 1969 22 June 1970] 52281/70 Heading G1R A flow metering device of the pressure differential producing type includes a tube having a wall defining a throat 13 and a converging section 14 for guiding fluid thereto from an inlet region of larger cross-section 12, there being pressure taps for sensing pressure in the inlet region and in the throat 16, 17 wherein the shape of the tube wall is adapted to cause the fluid, at least once during its passage from the inlet region to the throat pressure sensing tap, to form a vena contracta and then to expand and re-attach to the wall at a point downstream of the vena contracta. As described the differential pressure is produced by a tube 11 of the Venturi type in which the wall includes a truncated conical section 18 tapering from an inlet region 12 to a throat region 13 and having a sharp continuous edge 21 at the throat end which produces a vena contracta in a liquid flowing through the tube. A second truncated conical section 19 has a similar edge 22 which produces a second vena contracta. Examples are described of tubes which produce one only vena contracta, Figs. 8, 9 (not shown) and four vena contracta, Fig. 6 (not shown). The upstream pressure tap 16 may be in the inlet region or after the first vena contracta, Fig. 6 (not shown) In all cases the throat pressure tap is situated at a point after the vena contracta at which the fluid is again attached to the wall of the tube in order to determine the true static pressure.