Decoking control valve using dynamic rod seal

A decoking control valve comprising a fluid inlet, a first outlet port, a second outlet port, a hydraulic rod seal, a guide ring, a cylinder and a piston disposed within the cylinder, the piston arranged to move along a direction of travel within the cylinder to allow selective fluid communication between the fluid inlet and the first outlet port and the second outlet port;

• wherein:
• each of the hydraulic rod seal and guide ring are housed within a respective groove formed within the cylinder;
• the hydraulic rod seal comprises a seal ring which engages the piston such that the seal ring is energized by a pressure created by the inlet fluid acting on an activator such that the pressure is equalized across the seal ring immediately before the piston is retracted from the seal ring, the seal ring being energized at one of the first and second outlet ports at a time;
• and
• the guide ring is axially separated relative to the hydraulic rod seal by a distance such that the piston can only be engaged with one or the other of the hydraulic rod seal and guide ring at a time as the piston moves along the direction of travel within the cylinder.