What mistake did the operator make when repacking the gate valve regarding the valve plug?

The choice indicating that the operator should have left the plug out for a short period of time highlights an important aspect of maintaining gate valves during repairs or repacking. When repacking a gate valve, it's crucial to allow for a brief moment where the valve is open, and the plug is removed, to ensure old packing material and debris are completely cleared out without any obstruction. This also allows for a proper fit of the new packing material around the plug.

Keeping the plug out temporarily changes the positioning of the valve, enabling the operator to check the condition of the valve seat and ensure that the new packing is applied correctly without interference from the plug. This practice can effectively prevent misalignment or malfunction of the valve after it is reassembled, ensuring better sealing and easier operation in the long run.

Alternative options may suggest other actions related to the maintenance of the valve, but they do not emphasize the importance of temporarily removing the plug during the packing process, which directly contributes to the longevity and efficiency of the gate valve operation.