Introduction
This is a 3D model of a Backflow Preventer.
3D Model Annotations
Backflow Preventer
Backflow preventers are a type of check valve (non-return valve) used to prevent flow in a reverse direction to that which was intended. This particular 3D model shows a backflow preventer with two check valves and one relief valve.
Check Valve
This type of check valve consists primarily of a spring and disc. The disc presses against the seat in order to stop fluid flow. The spring provides residual force to close the valve. If the system pressure should exceed a given setpoint, the residual force of the spring will be exceeded, and the valve will open. Springs must be periodically inspected to ensure the desired lifting/opening pressure is maintained; corroded, dirty, or worn springs, may lead to the valve not operating as intended.
Relief Valve
Should the pressure between the two check valves exceed a certain value, the relief valve will open, and the pressure will be relieved. Relief valves are spring loaded pressure relief devices. Should the spring become worn over time, it may lift at a lower pressure. If the spring becomes dirty or corroded, it may lift at a higher pressure. For this reason, all relief valves should be periodically inspected and maintained (e.g. annually).
Main Inlet
Fluid flows into the valve through this connection.
Main Outlet
Fluid exits the valve through this connection.
Body
The body is the main pressure boundary of the valve, it may be manufactured from a single piece or multiple pieces.
Enjoying this article? Then be sure to check out our Introduction to Valves Video Course! The course has a quiz, handbook, and you will receive a certificate when you finish the course. Enjoy!
Additional Resources
https://en.wikipedia.org/wiki/Backflow_prevention_device
https://www.qrfs.com/blog/340-how-does-a-backflow-preventer-work