System, method and apparatus for combined ball segment valve and check valve

A fluid system fin handling a flammable working fluid, the fluid system comprising:

• an upstream fluid component;
• a downstream fluid component;
• a source of a pressurized non-flammable fluid;
• and
• a valve apparatus having an inlet fluidly coupled to the upstream component and an outlet fluidly coupled to the downstream component such that a flow path is defined between the upstream fluid component and the downstream component through the valve apparatus, the valve apparatus comprising:
• a ball segment operable to he rotated to a closed position wherein a generally curved end of the ball segment is in sealing engagement with ball segment valve seat to prevent flow of the working fluid through the outlet, and operable to be rotated to an open position wherein the generally curved end of the ball segment is at least partially disengaged with the ball segment valve seat to permit flow of the working fluid through the outlet;
• and
• at least one flapper door disposed operable to be rotated to a closed position wherein the at least one flapper door is in sealing engagement with a flapper valve seat to prevent flow of the working fluid through the inlet in a first direction, and operable to be rotated to an open position wherein the at least one flapper door is at least partially disengaged with the flapper valve seat to permit flow of the working, fluid through the inlet in a second direction;
• an isolated chamber defined between the at least one flapper door and the ball segment when the at least one flapper door and the ball segment are both in their respective closed positions;
• and
• a bleed port extending between the isolated chamber and an exterior of the valve apparatus, the bleed port fluidly coupled to the source of the pressurized non-flammable fluid to permit the non-flammable fluid to pressurize the isolated chamber and thereby urge the ball segment toward the ball segment valve seat and at least one flapper door toward the flapper valve seat.

A method of fluidly isolating a downstream fluid component from an upstream fluid component in a fluid system for handling as flammable working fluid to facilitate safely maintaining the downstream fluid component, the method comprising the steps of:

• (a) providing a check valve at downstream location with respect to the upstream component, the check valve including at least one flapper door operable to be rotated to a closed position wherein the at least one flapper door is in sealing engagement with a flapper valve seat to prevent flow of the working fluid in a first upstream direction, and operable to be rotated to an open position wherein the at least one flapper door is at least partially disengaged with the flapper valve seat to permit flow of the working fluid in a second downstream direction;
• (b) providing a ball segment valve at a downstream location with respect to the check valve that is an upstream location with respect to the downstream component, the ball segment valve including a ball segment operable to be rotated to a closed position wherein a generally curved end of the ball segment is in sealing engagement with a ball segment valve seat to prevent flow of the working fluid through the ball segment valve, and operable to be rotated to an open position wherein the generally curved end of the ball segment is at least partially disengaged with the ball segment valve seat to permit flow of the working fluid through the ball segment valve;
• (c) inducing the ball segment to rotate to the closed position thereof;
• (d) inducing the at least one flapper door to rotate to the closed position thereof;
• and
• (e) providing a pressurized non-flammable fluid to an isolated chamber defined between the at least one flapper door and the ball segment to thereby urge the ball segment toward the ball segment valve seat and at least one flapper door toward the flapper valve seat.