Torque-Isolating Valve Actuator With Non-Rising Stem
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric actuators used in deheading coke drums face challenges such as limited space requirements, increased wear due to torsional loads, unpredictable lifespan, inconsistent thrust output, and inability to operate quickly enough to mitigate dangerous conditions during the decoking process.
Innovation Solution
A torque isolating valve actuator system that includes an actuator housing, a nut housing with guide channels and rollers, anti-rotation rods to prevent rotation of the nut housing, and a non-rising hollow stem to shield the stem from torque forces, allowing for compact design and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a conventional electric actuator is used to drive the valve stem, then the actuator can provide the necessary torque to move the valve, but the stem must be oversized to withstand torsional loads and the actuator housing becomes excessively large
Solution Approach 1:
The actuator system is segmented into two independent functional components: a torque generation system (planetary gear set and motor) and a linear motion system (screw shaft and nut). The torque is generated in the torque system and transferred through the screw mechanism to produce linear motion, separating the torque capacity requirements from the stem sizing requirements.
Solution Approach 2:
A screw shaft acts as an intermediary mechanism between the rotational torque output and the linear stem motion. The screw threads convert rotational torque into linear thrust, allowing the stem to be sized for thrust loads only rather than combined torque and thrust loads.
2Ease of operation
If the stem is extended beyond the actuator to accommodate the open position, then the valve can be operated, but additional deck space of several feet is required
Solution Approach 1:
Instead of extending the stem outward from the actuator, the design uses a non-rising stem where the nut housing moves along the screw shaft within the actuator housing. The linear motion is contained within the actuator boundaries, eliminating the need for extended stem clearance space.
Solution Approach 2:
The nut housing containing the linear motion mechanism is nested within the actuator housing. The screw shaft passes through the hollow non-rising stem, and the entire linear motion system is contained within the actuator footprint, allowing compact installation with minimal deck space.
3Productivity
If prior art electric actuators are used, then the actuator can move the gate, but torsional loads cause increased wear on system elements within the valve
Solution Approach 1:
The direct-drive mechanical connection between motor and stem is replaced with a screw mechanism (planetary roller screw). This substitution converts rotational motion to linear motion through threaded engagement, eliminating torsional loads from the stem and associated wear on valve elements while maintaining actuation speed.
4Strength
If a larger stem is used to withstand torque forces, then the stem can handle the loads, but the actuator housing size increases and space becomes constrained
Solution Approach 1:
The torque function is extracted from the stem and handled by a dedicated torque generation system (motor and planetary gear set). The stem is relieved of torque responsibilities and sized only for linear thrust loads, reducing its required size and the overall actuator housing volume.
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 torque isolating valve actuator effectively reduces the size of the actuator housing, minimizes wear and misalignment due to torsional forces, provides consistent thrust output, and enables faster operation, thereby enhancing safety and reducing downtime in coke drum decoking processes.
Implementation Method 1
a planetary roller screw configured to convert the rotation of the screw to movement of the nut housing along the screw shaft
Implementation Method 2
anti-rotation rods disposed within the actuator housing and connected to the actuator housing and positioned outside the nut housing and passing through the guide channels wherein the guide channels and anti-rotation rods are configured to prevent the nut housing from rotating
Data Source
Figure 1
Figure 2
Figure 3
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.