Ontario Operator-in-Training (OIT) Practice Exam

What function do gate valves serve in water pipelines?

1. Regulate pressure

2. Control flow of liquid

3. Completely stop the flow

4. Prevent backflow

The correct answer is: Completely stop the flow

Gate valves are specifically designed to provide a fully open or fully closed position, making them ideal for applications where a complete stop of fluid flow is required. When the gate valve is fully opened, it allows for unrestricted flow through the pipeline, while closing the valve creates a tight seal that stops the flow entirely. This characteristic of completely stopping the flow is essential in various contexts such as maintenance, allowing for safe repair work without the risk of water pressure causing leaks or flooding. Although gate valves can influence flow to some extent, their primary function is not to regulate or control the flow but to isolate sections of the pipeline. Other valve types, such as globe valves or ball valves, are often utilized for flow regulation. In terms of preventing backflow, that function is typically addressed by check valves. Therefore, the main role of gate valves in water pipelines centers around their ability to stop the flow completely, making them crucial for system control during maintenance and emergencies.