Valve with pressure seal protection

A method of flowing particulate material and carrier gas from an inlet to an outlet of a valve, under the action of a pressure drop across the valve from the inlet to the outlet, the method comprising:

• providing the valve having;
• a closure member disposed in a fluid passage that extends from the inlet to the outlet, the closure member having a convex sealing surface;
• and a resilient sealing ring extending around the fluid passage between the inlet and the outlet, the sealing ring being in a first configuration in which the sealing ring forms a seal around a circumference of the convex sealing surface;
• moving the sealing ring to a second configuration to provide a circumferential gap between the convex sealing surface and the sealing ring;
• flowing particulate material and carrier gas from the inlet to the outlet;
• by increasing the velocity of the flow to a maximum velocity at a minimum clearance between the inlet and the circumferential gap;
• and then decreasing the velocity of the flow through the circumferential gap.

A particulate material conveying apparatus comprising a pressure vessel having an outlet port;

• and a valve therebetween;
• wherein the valve has a valve inlet and a valve outlet and the valve inlet is coupled to the pressure vessel outlet;
• and
• wherein the valve comprises:
• a body defining the inlet, the outlet and a fluid passage extending between the inlet and the outlet;
• a closure member disposed in the fluid passage between the inlet and the outlet, having a convex sealing surface;
• wherein the closure member is rotatable between a closed position in which the closure member extends across the fluid passage with the convex sealing surface oriented towards the inlet;
• and an open position in which fluid is able to flow through the fluid passage from the inlet to the outlet;
• a resilient sealing ring extending around the fluid passage between the inlet and the outlet;
• and, when the closure member is in the closed position;
• wherein the sealing ring is moveable between a first configuration in which the sealing ring forms a seal around a circumference of the convex sealing surface;
• and a second position in which the valve comprises a circumferential gap between the convex sealing surface and the sealing ring;
• wherein the body defines a fluid-directing surface extending around the fluid passage between the inlet and the sealing ring;
• and
• when the closure member is in the closed position, an annular clearance is defined between the fluid-directing surface and the convex sealing surface, which tapers towards the sealing ring to a minimum annular clearance, wherein the minimum annular clearance is less than the circumferential gap.