Quiet Running at Ravenswood

Recently CCI had the opportunity to supply a turbine bypass system to Stone and Webster’s Ravenswood combined cycle power plant using an air cooled condenser. The plant is a 250 MW unit, with a triple pressure steam system. The plant is located in Long Island City, New York, just north of the Queensboro bridge on the East River . The air cooled condenser is mounted on the roof of the power plant, with the turbine and bypass system ducting running up the side of the building.

The HP bypass system incorporates CCI’s DRAG® technology designed to eliminate the problems of noise, erosion and vibration. This is done through the advanced design of the DRAG® disk stack which controls fluid velocities by forcing the fluid through a series of right angle turns. These turns have been scientifically calculated to achieve low fluid velocities consistent with Ravenswood’s needs. The system is also supplied with a BTG DAMD desuperheater to reduce the enthalpy of the steam to 1155 BTU/lb. for discharging the steam to the condenser. Instead of providing a traditional dump tube to discharge steam into the condenser ducting, CCI will be supplying a multistage DRAG® resistor for discharging the steam into the ducting, and is mounted inside the duct on the side of the building. The DRAG® resistor will eliminate one of the primary noise sources in the bypass to condenser systems.

Also being supplied is an IP bypass system that includes a DRAG ® angle valve measuring 12-in. x 16-in. (300-mm x 400-mm), and an LP turbine bypass system that includes an angle valve that measures 12-in. x 12-in. (300-mm x 300-mm). IP and LP bypass systems will include low noise drilled holed dump tubes in order to meet the very low noise requirements. BTG DAMD and DAO desuperheaters are used to reduce the enthalpy to required levels.

With conventional bypass systems installed on air cooled condenser units, it is not usual to have near field noise levels of 110 dBA near the condenser ducting, and have far field noise levels of 70 dBA at 4000 ft (1200 m) from plant. CCI has designed the system to be able to meet the Ravenswood 55 dBA noise level requirement within 1000 ft (305 m) from the plant to allow night time operation of the bypass system.

By supplying this unique turbine bypass system with DRAG® valves, BTG desuperheaters, DRAG® resistors and low noise dump tubes, CCI is helping to ensure that Ravenswood will have flexible operating hours, and short and reliable startup times.

Published in SOLUTIONS Spring 2003