Ontario Operator-in-Training (OIT) Practice Exam

Which of the following is NOT considered an isolation valve?

1. Butterfly valve

2. Gate valve

3. Check valve

4. Ball valve

The correct answer is: Check valve

A check valve is not considered an isolation valve because its primary function is to allow fluid to flow in one direction while preventing backflow. This design is crucial for maintaining system integrity and preventing reverse flow, especially in piping systems that require flow control in a specific direction. In contrast, isolation valves, such as butterfly valves, gate valves, and ball valves, are used to completely shut off the flow of fluid in a pipeline. They can be opened or closed to isolate a section of the system for maintenance or to control the flow as needed. Therefore, the check valve's role is fundamentally different, focusing on flow control rather than isolation, which clearly distinguishes it from the other options listed.