Balanced Valve Trim With Ports for Lower Stem Force
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Solution Overview
Problem
High recovery valves experience significant stem forces due to pressure differentials across the valve plug, leading to increased wear and potential performance issues, particularly at choked flow conditions.
Innovation Solution
Incorporating balance ports along the outer surface of the valve plug, spaced between the shoulder and tip, to equalize pressures and reduce stem forces by venting fluid through these ports, which connect to a central bore and extend axially through the valve plug, thereby balancing pressure forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a high recovery valve design is used to minimize flow stream energy dissipation, then pressure recovery is improved, but stem forces increase due to pressure differential across the valve plug
Solution Approach 1:
The valve plug is segmented into multiple pressure zones using balance ports that create separate chambers. These ports allow pressure equalization between the upstream and downstream sides of the valve plug, dividing the single large force into smaller manageable forces that act on different segments of the plug surface.
Solution Approach 2:
Balance ports serve as intermediary channels that mediate the pressure differential across the valve plug. These ports introduce a pressure equalization mechanism that reduces the net force on the stem by allowing fluid communication between high and low pressure zones, effectively acting as a mediator to balance forces.
2Force
If balance ports are added to the valve plug to reduce stem forces, then stem force is reduced, but device complexity increases
Solution Approach 1:
The balance ports are merged with the existing valve plug structure rather than being separate components. The ports are integrated into the plug body and work in conjunction with the valve seat and flow passage, combining multiple functions (flow control and force balance) into a single integrated trim assembly.
Solution Approach 2:
The valve plug serves multiple functions: it acts as both the flow control element and the force balance mechanism. The balance ports are incorporated into the plug structure, allowing the same component to perform both flow modulation and stem force reduction, eliminating the need for separate balancing mechanisms.
3Force
If the balance port is positioned closer to the throat to improve pressure equalization, then stem force reduction is enhanced, but pressure recovery may be compromised
Solution Approach 1:
Different regions of the valve plug are assigned different functions based on their location. The balance port positioning creates local pressure equalization zones that specifically address stem force reduction in critical areas while maintaining the overall pressure recovery characteristics of the high recovery valve design in other regions.
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
The solution effectively reduces peak stem forces and improves pressure recovery, leading to enhanced valve performance and reduced wear, especially during choked flow transitions, while allowing for more gradual fluid expansion downstream.
Implementation Method 1
the balance port is vented through the valve plug to equalize a first pressure at a location on the outer surface of the valve plug with a second pressure at a location on the opposite end of the valve plug
Data Source
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AI summary
Valve trim (20) for a valve includes a valve plug (24) having one or more balance ports (60) located along the outer surface (46) of a tapered nose portion (44) of the valve plug. Each balance port is located to be downstream of the throat (52) and spaced from the tip (50) of the tapered nose portion of the valve plug. The valve trim may be use, for example, in a high recovery angle body valve. A high recovery valve with the valve trim may have better recovery performance as well as a smaller spike in stem force through the choked flow transition point. A method of reducing stem forces on a valve stem of sliding stem valve is also provided.