Decoking control valve using dynamic rod seal

An assembly for controlling flow of a decoking fluid to a coke drum, the assembly comprising:

• a fluid supply conduit;
• a decoking tool in fluid communication with the fluid supply conduit;
• and
• a control valve fluidly disposed between the fluid supply conduit and the decoking tool, the control valve comprising:
• a cylinder defining an inlet port and a plurality of outlet ports each of which are in fluid communication with the fluid supply conduit;
• a plurality of hydraulic rod seals each housed within a respective groove that is formed within a wall of the cylinder;
• and
• a piston disposed within and arranged to travel within the axial dimension to allow selective fluid communication between the inlet port and the plurality of outlet ports, wherein:
• the plurality of hydraulic rod seals are separated from one another therein by an axial dimension such that only one of the plurality of hydraulic rod seals is in contact with the piston at a time;
• the piston, the cylinder and the plurality of hydraulic rod seals cooperative with one another during control valve operation to fluidly isolate the inlet port from one of the plurality of outlet ports, and
• the piston further defining at least one flowpath formed therethrough such that during movement of the piston in response to differential axial pressure being applied thereto from the pressurized decoking fluid, the piston selectively engages with one of the plurality of hydraulic rod seals such that a portion of the pressurized decoking fluid flows through the at least one flowpath to substantially equalize an axial fluid pressure across such hydraulic rod seal.

A method of sealing a flow of pressurized decoking fluid, the method comprising:

• introducing a pressurized decoking fluid into a control valve comprising:
• a cylinder defining an inlet port and a plurality of outlet ports each of which are in fluid communication with the fluid supply conduit;
• a plurality of hydraulic rod seals each housed within a respective groove that is formed within a wall of the cylinder;
• and
• a piston disposed within and arranged to travel within the axial dimension of the cylinder, the piston defining at one least flowpath formed therethrough, wherein:
• the plurality of hydraulic rod seals are separated from one another therein by an axial dimension such that only one of the plurality of hydraulic rod seals is in contact with the piston at a time;
• and
• operating the control valve such that during movement of the piston in response to differential axial pressure being applied thereto from the pressurized decoking fluid, the piston selectively engages with one of the plurality of hydraulic rod seals such that a portion of the pressurized decoking fluid flows through the at least one flowpath to substantially equalize an axial fluid pressure across such hydraulic rod seal.