Good Fortune Provided for Little Gypsy

When a control valve continues to be problematic despite good maintenance practices and skilled staff, it is the first clue that incorrect technology is being applied in that service, which is not suitable for the specific application requirements.

Recently this was the situation at Entergy Louisiana ’s Little Gypsy plant, where an existing boiler feedpump recirculation valve was extremely problematic. Packing and body gasket leaks resulted in catastrophic leaks straight to atmosphere. Since the valves were required to operate on/off twice a day, damage to the seating surface was prohibiting the valves from achieving tight shutoff. This leakage downstream of the valve was limiting the plant power capability below full capacity.

To aid Little Gypsy, CCI provided a 4-in. (100-mm) DRAG® valve with a unique trim design that incorporates a stack of tortuous-path disks that permit multi-stage pressure reduction over the entire stroke of the valve. Feedwater pressure is continually dissipated at a controlled velocity by being forced through a number of channels with right-angle bends etched into the disks. To ensure absolutely tight shutoff, the BFP recirculation valve is also provided with pressurized seating. When the valve is closed, upstream pressure is applied above the main plug by way of a multi-stage bleed pin which controls flow to the bonnet. This provides a seating load equal to the inlet pressure times and the full area of the main plug. In Little Gypsy’s case this is extremely important since the recirculation valve is piped straight to condenser. Any flow that leaks pass the recirculation valve to condenser results in lost heat and lost MW production. The gain in lost MW will undoubtedly offset the cost of the valves being installed. By providing a valve that eliminates cavitation and provides tight shutoff CCI can ensure customers of uninterrupted run time and higher profit margins.