Fluid Regulator Valve Stem Sliding Coupling Seal Protection
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Solution Overview
Problem
Existing back-pressure fluid regulators suffer from high seat loads on seals during maintenance or shipment, leading to potential damage and leakage due to the rigid coupling between the valve plug and valve stem, which imparts a pre-set force even when control pressure is absent.
Innovation Solution
The fluid regulator decouples the loading element from the flow control member when it engages the valve seat, allowing the valve stem to slide through, thereby reducing the seat load and preventing seal damage, and adjusts the pre-set pressure without applying a large load to the seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the valve plug and valve stem are rigidly coupled together via a fastener, then the valve plug always moves together with the diaphragm and remains operatively coupled to the pre-set control force, but the pre-set load imparts a relatively high seat load to the valve plug when control pressure is absent, which can damage the seal and cause leakage
Solution Approach 1:
The connection between the valve stem and valve plug is changed from a rigid fixed coupling to a dynamic sliding coupling. The valve stem can slide within the valve plug, allowing the pre-set control force to be applied to the diaphragm without being transmitted as high seat load to the seal when control pressure is absent. This dynamic mechanism enables the system to adapt its force transmission characteristics based on operating conditions.
Solution Approach 2:
The rigid coupling between valve stem and valve plug is segmented into separate movable components. The valve stem is separated from the valve plug body, with only the flow control portion of the valve plug moving with the diaphragm while the seal engagement portion remains independent. This segmentation allows the pre-set force to act on the diaphragm without being imparted to the seal.
2Ease of operation
If the valve plug is rigidly coupled to the valve stem, then the pre-set force is always imparted on the seal when the valve plug engages the valve seat, but this causes potential seal damage during maintenance or shipment when control pressure is absent
Solution Approach 1:
The valve stem connection is made dynamic through a sliding mechanism that allows relative movement between the valve stem and valve plug. During normal operation, the valve stem moves with the diaphragm to control valve opening. During maintenance or shipment when control pressure is absent, the valve stem can slide independently, preventing the pre-set force from damaging the seal.
Solution Approach 2:
A sliding interface acts as an intermediary mechanism between the valve stem and valve plug. This intermediary allows the pre-set control force to be transmitted to the diaphragm for valve control while preventing the transmission of high seat loads to the seal, thus mediating between the conflicting requirements of valve control and seal protection.
3Reliability
If a pre-set control force is applied to the diaphragm to regulate upstream pressure, then the valve plug can be urged to seal against the valve seat, but the pre-set load cannot be adjusted without applying a large load to the seal
Solution Approach 1:
The pre-set control force mechanism is made adjustable through the sliding connection. The valve stem can be repositioned along the valve plug to change the effective leverage or spring compression, allowing adjustment of the pre-set force without requiring high seat loads. This dynamic adjustment capability enables flexible pressure regulation settings.
Solution Approach 2:
The adjustment mechanism is segmented into independent components where the valve stem position relative to the valve plug can be modified without affecting the seal engagement. This allows the pre-set control force to be adjusted while the seal remains protected from excessive loads, separating the adjustment function from the sealing function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly reduces the risk of seal damage during maintenance or shipment by minimizing the seat load, ensuring reliable operation and preventing leaks, while allowing for adjustable pre-set forces without damaging the seal.
Implementation Method 1
the diaphragm moves the valve plug in response to a difference between the pressure of the fluid at the inlet (i.e., the force applied to the second side of the diaphragm) and the pre-set control force (i.e., the force applied to the first side of the diaphragm)
Implementation Method 2
the valve plug sealingly engages the valve seat
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
Valve stem and valve plug apparatus for use with fluid regulators are described herein. An example fluid regulator includes a flow control member (258) having a body (266) that includes a longitudinal bore (280) between a first end (282) and a second end (284) and a valve stem (226) is disposed in the bore of the flow control member. A connector (286) slidably couples the valve stem and the flow control member such that the connector moves away from the flow control member to relieve the flow control member of a loading force imparted by a loading element (206) of the fluid regulator when the flow control member sealingly engages a valve seat (254) of the fluid regulator.