Backflow Preventer Relief Discharge Detector

Author(s) Information

Qinyanggang Li, California Polytechnic State University, San Luis ObispoFollow
Colin Thomas Urban, California Polytechnic State University, San Luis ObispoFollow
Aaron Anthony Escamilla, California Polytechnic State University, San Luis ObispoFollow

College - Author 1

College of Engineering

Department - Author 1

Mechanical Engineering Department

Degree Name - Author 1

BS in Mechanical Engineering

College - Author 2

College of Engineering

Department - Author 2

Mechanical Engineering Department

Degree - Author 2

BS in Mechanical Engineering

College - Author 3

College of Engineering

Department - Author 3

Mechanical Engineering Department

Degree - Author 3

BS in Mechanical Engineering

Date

6-2024

Primary Advisor

Eileen Rossman, College of Engineering, Mechanical Engineering Department

Abstract/Summary

This project aims to fulfill a critical need in Zurn's backflow prevention products by developing a versatile external sensor assembly. This assembly is specifically designed to integrate smoothly with the relief valve vent port of the Model 975XL3 RP Backflow Preventer, available in 1-inch and 2-inch sizes. Its primary function is to detect water discharge and send an ON/OFF signal, enabling cloud-based monitoring or in-house alarm system notification of valve status. The sensor assembly ensures high reliability and flexibility with air gap installations, requiring little to no monitoring after installation. By utilizing existing mounting holes on the valve, the design employs for quick and easy setup that does not require a trained technician. The electronic components are also straightforward and just consists of wires and a switch. The 3D printed structure attaches to the valve plate using screws and contains a mechanical limit switch that is activated by a high enough water flow. This switch connects to an alarm system suitable for both indoor and outdoor use, with the design differing only in size to accommodate various valve diameters (1- and 2-inch).

Since the Critical Design Review (CDR), several significant changes have been made to enhance functionality and meet engineering specifications. The most notable change is the addition of vertically extruded mounts with counterbores for air gap screws, replacing an unsuccessful funnel design. To address water leakage through the switch lever slot, a sloped roof section and a 3D printed slot blocker were incorporated, significantly reducing water exposure to the electronics. A circular water plate was added to the switch lever to improve sensitivity at low flow rates, and switch mounting holes were adjusted to slots for customizable flow rate triggering and better manufacturing tolerance. This project document covers the design, implementation, verification, and future recommendations. The design section details changes since the CDR and explains the final design decisions. The design verification section confirms that all critical specifications are met and provides justification for these decisions. Future recommendations are included to guide subsequent project iterations.

For mass production, we recommend manufacturing the mount and tube as a single unit using injection-molded plastic. Similarly, the water blocker and plate fin should also be injectionmolded plastic. Future engineers should focus on simplifying the assembly process. While the current assembly is easy enough for non-engineers, the small dimensions of the tube can sometimes make fitting the fin challenging. Constructing a rig or making minor design adjustments could enhance the speed and consistency of the assembly process. The next steps involve refining the design and iterating the current 1- and 2-inch designs to work with all valves in the 975XL3 series. Overall, we are pleased with our final design, which effectively senses water discharge at low flow rates and provides consistent results after extensive testing. The simplicity of assembly and ease of manufacturing are significant achievements. The project required frequent design iterations based on testing outcomes at the Zurn facility, embodying the true nature of iterative design where each failure provided insights for improvement.

URL: https://digitalcommons.calpoly.edu/mesp/754