GB1258396A - - Google Patents

Abstract

1,258,396. Valves. W. S. MARTIN. 23 May, 1969 [26 Feb., 1968], No. 9120/68. Heading F2V. Pressure and vacuum relief valve e.g. for petroleum storage tanks on ship or shore, comprises a first flap member mounted for pivotal movement in a tubular housing, urged to a rest position in which it closes the housing and adapted to pivot away from the rest position in response to pressure from one side, and a second flap member pivotable about the same axis as the first member, urged to a position in which it closes an aperture in the first member and pivotable away from the closed position in response to pressure from the other side. As shown, a first circular flap 22 is pivoted about an offset axis 24 so that it is biased by gravity to closed position against a semi-circular seat 26. A second circular flap 28 within an aperture in the first one, is pivoted on the same axis 24 which is offset in the opposite direction from the diameter E of this second flap. The second flap is weighted to closed position by a plate segment 30 which overlaps the aperture to stop the flap 28 in closed position. Excess pressure beneath the valve is relieved by opening of the first flap and vacuum beneath the valve by opening of the second flap. In another embodiment, Figs. 3-5 (not shown), a rectangular frame 40 for mounting in a vertical conduit is partitioned to form two parallel flow ducts (45, 46) providing respective valve seats at opposite ends respectively of the frame. A pair of first flaps (52, 54) engaging the seats are fixed to two F-shaped arms (49) pivoted on a shaft (48). A second pair of flaps (60, 62) which close apertures in the first flaps, are fixed to similar arms (57) pivoted on the same shaft (48). The arrangement is such that the first flaps open to relieve excess pressure and the second pair to relieve vacuum. The device is gravity loaded to closed position, or springs may be used instead.