Control Valve Grounding Contact for Low-Wear Static Discharge
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Solution Overview
Problem
Control valves in process plants face issues with static charges leading to sparks due to lack of effective grounding, especially when there is no direct metal-to-metal contact, and existing solutions like electrostatic draining devices and electrical contact switches are complex and prone to abrasion.
Innovation Solution
A control valve design featuring a stationary contact holder with an axially movable, conductive annular spring that rolls along the lifting rod, providing a low-friction, almost wear-free electrical connection between the lifting rod and the valve housing, ensuring grounding and preventing electrostatic charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a stationary contact holder with an axially movable annular spring is used to electrically contact the lifting rod, then the friction and wear between the contact components are minimized, but the complexity of the electrical contact mechanism increases compared to direct metal-to-metal contact
Solution Approach 1:
The annular spring is designed to be axially movable within the contact holder, allowing it to dynamically adapt to the lifting rod's axial movements. This dynamic configuration enables the spring to roll along the lifting rod during axial displacement, transforming sliding friction into rolling friction and significantly reducing wear on both the spring and the lifting rod surface.
Solution Approach 2:
The contact mechanism utilizes elastic deformation of the annular spring to accommodate axial movements. By changing the physical state from rigid fixed contact to elastic movable contact, the system achieves low-friction operation while maintaining reliable electrical connection throughout the lifting rod's travel range.
2Force
If the annular spring is allowed to move axially to roll along the lifting rod, then friction is reduced to minimum, but the precision of electrical contact may be compromised due to movement variability
Solution Approach 1:
The annular spring acts as an intermediary element between the fixed contact holder and the moving lifting rod. It absorbs and accommodates axial movements through its elastic deformation and rolling motion, while maintaining continuous and stable electrical contact. The spring's elasticity ensures that contact pressure is maintained within optimal ranges despite positional variations.
Solution Approach 2:
The annular spring is pre-loaded with an appropriate force to ensure continuous contact with the lifting rod throughout its axial movement range. This pre-loading creates a cushioning effect that maintains stable electrical connection while allowing the spring to roll and reduce friction during operation.
3Reliability
If the annular spring is pressed against the lifting rod with sufficient preload to ensure electrical contact, then reliable galvanic connection is achieved, but the wear on the non-contoured lifting rod surface increases
Solution Approach 1:
The annular spring is designed to roll along the lifting rod during axial movements rather than sliding against it. This dynamic rolling contact significantly reduces friction and wear on the lifting rod surface while maintaining sufficient contact pressure for reliable electrical connection. The rolling motion occurs as the spring moves axially within the contact holder in response to lifting rod displacement.
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 achieves a reliable, low-friction galvanic connection with minimal wear, effectively preventing electrostatic charging and ensuring safe grounding of the valve body in all positions, thereby reducing the risk of sparks and extending the service life of the contact components.
Implementation Method 1
an annular spring (36) which is axially movably mounted in the contact holder and which is pressed against the lifting rod by a spring force
Implementation Method 2
the annular spring is capable of moving to such an extent in the axial direction, both relative to the lifting rod and within an axial limit of the contact holder, that the annular spring can roll along the lifting rod in the contact holder
Implementation Method 3
In the axial direction, on either side and in an electrically conductive manner, the contact holder holds an electrically conductive annular coil
Data Source
AI summary
The invention relates to a control valve for adjusting a process fluid flow of a process plant, comprising a valve housing with a valve seat and a valve member connected to a valve rod, which cooperates with the valve seat for opening and closing the control valve, wherein the valve rod is electrically connected to the valve housing through a contact device. The invention is characterized in that a measuring device for the ohmic transition resistance measurement of the contact device is provided, and that the measuring device is arranged in a measuring line that connects the valve housing to the valve rod.