Torque-Isolating Valve Actuator With Planetary Roller Screw
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Solution Overview
Problem
Existing electric actuators in the hydrocarbon processing industry face issues with size constraints, wear, and inconsistent thrust output, leading to increased downtime and safety concerns during the decoking process, particularly due to the transfer of torque forces to the stem, which affects alignment and longevity.
Innovation Solution
A torque isolating valve actuator system that shields the stem from torque forces using a nut housing with guide channels and anti-rotation rods, allowing the stem to be sized independently of torque requirements, and utilizing a non-rising hollow stem with rollers and a screw shaft to prevent misalignment and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stem is sized to resist torque forces, then the stem can withstand the torque force, but the actuator housing size increases and deck space requirement increases
Solution Approach 1:
The patent divides the force transmission path into two separate functions: the stem handles only axial thrust forces, while a separate mechanical advantage mechanism (planetary gear system) handles torque multiplication. This segmentation allows the stem to be sized for thrust only, reducing its diameter and the overall actuator housing size, thereby reducing deck space requirements.
Solution Approach 2:
The patent introduces a planetary gear mechanism as an intermediary between the motor and the stem. This intermediary provides mechanical advantage to multiply torque without requiring the stem to be oversized, thus resolving the contradiction between stem strength requirements and space constraints.
2Strength
If the stem is sized to resist torque forces, then the stem can withstand the torque force, but the stem and actuator components experience increased wear
Solution Approach 1:
By separating the torque transmission function from the stem, the patent eliminates torsional stresses and misalignment forces from the stem. The stem only experiences axial thrust forces, which significantly reduces wear on the stem threads and valve internal components, improving reliability.
Solution Approach 2:
The patent replaces the traditional direct-drive mechanical system with a planetary gear mechanism that provides mechanical advantage. This substitution allows torque to be multiplied through the gear system rather than being transmitted directly through the stem, reducing wear and improving component longevity.
3Power
If prior art electric actuators are used, then the actuator can produce torque, but the thrust output is inconsistent over the actuator lifespan
Solution Approach 1:
The patent replaces the direct mechanical connection system with a planetary gear mechanism that provides consistent mechanical advantage throughout the actuator's operational range. This ensures that thrust output remains consistent over the actuator lifespan, as the gear system maintains a fixed ratio between motor torque and stem thrust.
4Productivity
If prior art electric actuators are used, then the actuator can move the valve, but the actuator requires additional deck space during operation
Solution Approach 1:
By separating the torque multiplication function (planetary gear system) from the thrust transmission function (stem), the patent reduces the stem diameter required, thereby reducing the actuator housing size and overall deck space footprint while maintaining full valve operation capability.
Solution Approach 2:
The patent employs a non-rising stem design where the stem is nested within the actuator housing rather than extending outward. This nesting arrangement eliminates the need for additional deck space during valve operation, as the stem remains contained within the actuator footprint.
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 wear and misalignment, allows for consistent thrust output, and enhances safety by isolating torque forces, thereby improving the operational efficiency and longevity of the actuator system within limited space constraints.
Implementation Method 1
a planetary roller screw mechanism comprising a screw shaft, a nut housing, and rollers
Implementation Method 2
the screw shaft and the nut housing are configured to provide mechanical advantage to multiply a force applied to the screw shaft
Implementation Method 3
the anti-rotation rods and the guide channels are configured to prevent the nut housing from rotating
Data Source
AI summary
A low-volume non-rising stem gate valve comprising a hollow stem, planetary roller screw and anti-rotation rods. The anti-rotation rods isolate the torque force and maintain the alignment of the planetary roller screw with the stem and the screw shaft, thus reducing the amount of material necessary to support ordinary operational forces.