Bypass – Modulation and Shut off System

Basic data:

Plant: Combined Cycle Power Station
Country: Germany
Investor: ALSTOM POWER BOILER, Stuttgart
Dimensions: 17500 mm – girders

Bypass – Modulation and Shut off System
Bypass – Modulation and Shut off System


Raumag Janich received an order for an isolation and gas modulation speciality damper, installed in the integrated bypass duct of the waste heat recovery boiler. It should have 17500 mm long girders. This means the structure could be very prone to heat distortion, which would produce additional hazard at the plant.


The extreme blade span was only made possible by application of the new, patented, lattice supported blade design. The blades are made up of 17500 mm long latticed girders upon which the diaphragm plates are attached. Seals of the NICROFLEX – HIPERFORM, DBPa type were selected for this design because of their high resilience.


In an open position, high temperature gas can flow nearly unrestricted through the lattice support grid, and therefore, causes only minimal cross blade pressure drop. Since all the members of the lattice support structure are evenly swept by the hot flue gases, they heat up uniformly and thereby any distortions are averted. The chosen seals provide a high tightness even under these difficult service conditions.