Tennessee Wastewater Operator Practice Exam

When repacking gate valves that are in service, what should the operator do to minimize leaks?

1. Close the valve before repacking

2. Open the valve wide before repacking

3. Leave the valve idle for several hours

4. Replace the valve entirely

The correct answer is: Open the valve wide before repacking

To minimize leaks when repacking gate valves in service, it is important to understand the dynamics of valve operation and packing material behavior. Opening the valve wide before repacking allows for better access to the packing area and ensures that the packing material can be compressed evenly. When a gate valve is fully open, the gate is lifted away from the seat, reducing pressure against the packing. This creates a situation where the packing can be adjusted and replaced more effectively without the stress of the gate being fully seated against the valve body. Moreover, this approach helps in preventing packing damage that can occur if the valve is closed or partially closed during the repacking process. In contrast, closing the valve may increase the pressure on the packing material, making it more difficult to install new packing and potentially leading to improper sealing once the valve is put back into service. Leaving the valve idle for several hours does not contribute to minimizing leaks and may lead to other issues, such as sediment buildup. Replacing the valve entirely may be unnecessary and more costly, especially if the valve can be adequately maintained through repacking. Therefore, opening the valve wide provides an optimal condition for maintenance, reducing the likelihood of leaks when the valve is subsequently operated.