Apparatus and method for reducing actuator thrust requirements in a control valve

摘要

A trim assembly is provided with a cage with an internal surface and a cage port. A plug having an external surface is disposed in the cage and is operable between a closed position, a pressure balancing position and an open position. The trim assembly also includes a low friction flow restrictor disposed between the cage and the plug and a pressure energized seal disposed between the cage and the plug. A seal balancing volume defined by the internal surface of the cage, the external surface of the plug, the low friction flow restrictor and the pressure energized seal is provided. The seal balancing volume is in fluid communication with the cage port through the low friction flow restrictor and is maintained at a seal balancing volume pressure. The trim assembly further includes a pressure control assembly configured to vent the seal balancing volume.

主权项

1. A trim assembly, comprising:
a cage with an interior surface and a cage port; a plug disposed in the cage, the plug having an external surface and being operable between a closed position, a pressure balancing position, and an open position; a low friction flow restrictor disposed between the cage and the plug; a pressure energized seal disposed between the cage and the plug; a seal balancing volume; a pressure control assembly configured to pressurize the seal balancing volume; and a conduit in fluid communication with a volume at an upstream pressure when the plug is in the pressure balancing position, wherein the pressure control assembly is configured to allow fluid at the upstream pressure to flow into the seal balancing volume at a rate in which leakage of fluid through the low friction flow restrictor is less than flow of fluid into the seal balancing volume.