Complete Gas Turbine Exhaust By Pass Systems
The "Exhaust Gas by Pass System" will receive heat from exhaust of Gas Turbines resulting from Combustion process in Gas Turbines and will release Exhaust Gas to atmosphere (Simple Cycle) or will direct it toward existing HRSG (Heat Recovery Steam Generators) to generate Steam (Combined Cycle).
Each Exhaust Gas by Pass System consists of the following main parts;
- Stack
- Diffusers
- Diverters
- Silencers
- Fabric Expansion Joints
- Supporting Steel Structure
The stack system is being designed in accordance with "ASME STS 1" or equivalent European norms.
Stack (by-pass)
The steel stack which is generally internally insulated and lined with stainless steel sheets is designed to be supported on steel structure in accordance to ASME-STS 1.
The primary considerations in design and sizing of the stack are;
- Seismic and Wind loads,
- Available Draft and Draft requirements,
- Local environmental requirements,
- Local fire protection and regulations,
- Maximum permissible noise level,
- Flow velocity and exhaust gas pressure drop.
- Atmospheric conditions and corrosion protections
- Acid dew point consideration and material selection
- Thermal design and heat loss through surface
Diverter Damper
Pivot or Toggle armed diverter will contain a single operating blade, with inside truss reinforcement system and Insulation on blade which will have to withstand turbulent Exhaust flow of Gas Turbine. Due to single blade configuration of Diverter valve, it will be physically impossible to have both outlet ducts simultaneously closed.
Diverter will be equipped with electric or Hydraulic actuator for blade operation together with necessary limit switches for open and closed positions. Using the sealing air it will be possible to achieve %100 tightness when diverter is closed to one of the outlets (Stack or HRSG sides). Sealing air fans and motors (1 operating+ 1 stand by), piping and valves will be supplied together with diverter.
ENPRO is designing, manufacturing its own patented diverters for different turbine models by using its own know how and design knowledge.
Expansion Joints
The expansion joints to be used in "Exhaust Gas by Pass System" are non-metallic, internally insulated with stainless steel liners. The expansion joint fabric material must withstand the potential for stress caused by rapid temperature rise of gas turbine start ups. The expansion joints shall avoid wrapping, binding, cracking and gas leakage.
The expansion joints should handle both lateral and axial expansion and contractions. They are constructed with different designs according to the adjacent duct, whether it is internally or externally insulated. The flexible element will made up of different layers each with different characteristics to withstand various flow parameters. Expansion Joint will be in accordance to International ESA standards.