Balanced valve port for fluid regulator

A balanced port control assembly for a fluid flow control device, the assembly comprising:

• a port housing defining a central cylindrical opening;
• a valve stem having a central longitudinal axis and at least partly disposed in the port housing for reciprocating displacement along the central longitudinal axis;
• a valve plug coupled to the valve stem and defining a sealing surface adapted to selectively sealingly engage a valve port of the fluid flow control device;
• a balancing diaphragm operably coupled between the valve plug and the port housing, the balancing diaphragm having opposite first and second diaphragm surfaces;
• a balancing cavity defined in a portion of the port housing between an inner surface of the port housing and the first diaphragm surface of the balancing diaphragm;
• and a first pressure sensing passage extending through the valve plug and in fluid communication with the balancing cavity such that a fluid pressure resident on the sealing surface of the valve plug is equal to a fluid pressure resident in the balancing cavity to apply equal and opposite first and second forces to the sealing surface of the valve plug and the first surface of the balancing diaphragm, respectively, the first pressure sensing passage having an inlet portion extending through the valve plug along the central longitudinal axis of the valve stem˜and wherein the valve plug comprises at least one of:
• (a) a central bore extending along the central axis of the control element and a plug fastener disposed in the central bore and fixing the valve plug to the valve stem, the plug fastener defining at least a portion of the inlet portion of the first pressure sensing passage;
• and
• (b) an outer plug portion, an inner plug portion disposed radially inside of the outer plug portion, and at least one intermediate passage disposed between an outer wall of the inner plug portion and an inner wall of the outer plug portion, wherein the at least one intermediate passage defines at least one second pressure sensing passage extending through the valve plug and in fluid communication with the balancing cavity.

A balanced port control assembly for a fluid flow control device, the assembly comprising:

• a port housing defining a central cylindrical opening;
• a valve stem having a central longitudinal axis and at least partly disposed in the port housing for reciprocating displacement along the central longitudinal axis;
• a valve plug coupled to the valve stem and defining a sealing surface adapted to selectively sealingly engage a valve port of the fluid flow control device;
• a balancing diaphragm operably coupled between the valve plug and the port housing, the balancing diaphragm having opposite first and second diaphragm surfaces;
• a balancing cavity defined in a portion of the port housing between an inner surface of the port housing and the first diaphragm surface of the balancing diaphragm;
• and a pressure sensing labyrinth defined at least partly by the valve plug and providing fluid communication between the sealing surface of the valve plug and the balancing cavity such that fluid pressure resident on the sealing surface of the valve plug is equal to fluid pressure resident in the balancing cavity to apply equal and opposite first and second forces to the sealing surface of the valve plug and the first surface of the balancing diaphragm, respectively, the pressure sensing labyrinth comprising at least one first pressure sensing passage extending from the sealing surface and into the valve plug along the central axis of the valve stem and including at least one of:
• (a) wherein the pressure sensing labyrinth further comprises at least one second pressure sensing passage providing fluid communication between the sealing surface of the valve plug and the balancing cavity, at least a portion of the at least one second pressure sensing passage defined by the valve plug and disposed parallel to the first pressure sensing passage,
• (b) further comprising a seal member disposed in the at least one second pressure sensing passage and providing a fluid tight seal, and
• (c) wherein the valve plug further comprises a central bore extending along the central axis of the control element and a plug fastener disposed in the central bore and fixing the valve plug to the valve stem, the plug fastener defining at least a portion of the inlet portion of the first pressure sensing labyrinth.