In this Cameron-sponsored school project, my team and I were tasked with eliminating large steel coil springs from valve actuator mechanisms and devising a new means to control valve position under normal and power-loss conditions. We generated and analyzed alternative design concepts that have the capacity to store energy and provide a return force to move the valve to the fail-closed or fail-open position. The goal of the project was to select the most innovative and viable final design concept that decreases size, weight, and cost of the the actuator.
Requirements and Constraints
The functional requirements for the project included the ability to reverse-actuate under both normal and power-loss conditions and be able to reverse-actuate in 30 seconds for large valves and 5 seconds for small valves. The new design had to provide a return force between 876 lbf and 36,300 lbf to reverse the actuation. It must also be capable of operating in H2S (hydrogen sulphide), carbonic acid, and salt water environments at temperatures between 15°F and 150°F. Finally, the design had to fulfill ISO 1423 Appendix F PR2 requirements of 20 cycles at 50°F, 200 cycles at 77°F, and 20 cycles at 149°F.
As for geometry and weight restrictions, the new design was constrained to a circular cross-section, the allowable height was between 5.91 inches and 47.24 inches, and the weight of the proposed solution had to be between 3.75 lbf and 1,256 lbf. The electric energy available to the system was between 300 V and 6,000 V, and it was assumed that any needed hydraulic or pneumatic would be available before power-loss. Finally, the overall cost of the design could not exceed $200.
After an in-depth comparison of several designs, we chose a compressed gas solution as the optimal design. To prevent heat and pressure-loss of the gas, an optional resistive heating element was incorporated in the bottom of the piston chamber. For more details on the project, please download the full report.
DOWNLOAD FULL REPORT (9.4 MB)