If your staff is not experienced in initiating an emergency purge of hydrogen from the generator, personnel at Hermiston Generating Plant, a 474-MW, 7FA-powered 2 × 1 combined-cycle cogeneration facility have a solution to consider.
Hermiston developed an emergency hydrogen purge procedure during plant commissioning nearly 25 years ago. It required entering the collector compartment and opening the lower compartment where the purge valves are located. But this could be problematic in the event of fire and/or release of CO2 into the compartment.
The goal was to make an emergency purge safer for the individual performing this task. Several options were considered. Here’s what was done: Use the logic already in the Mark V Control Sequence Program and add logic to allow the control room to remotely initiate and purge hydrogen with no one near the generator. The relatively simple upgrade was facilitated by replacing the original hydrogen control cabinet with one from EOne.
Drawings of the successful mod are provided in the presentation. After the logic updates were completed, an emergency hydrogen purge was performed on each unit from the control room. Success! Today, the system is tested annually or when hydrogen is removed from the machine during extended maintenance shutdowns.