---
title: "Diverter / louver / guillotine damper"
description: "Dampers route, isolate or modulate flue-gas flow inside industrial ducting. Three principal types appear in power and process plants:"
canonical_url: "https://sylio.co/glossary/diverter-damper-louver-damper-guillotine-damper"
last_updated: "2026-06-28T02:29:33.534Z"
---

**Dampers** route, isolate or modulate flue-gas flow inside industrial ducting. Three principal types appear in power and process plants:

<table>
<thead>
  <tr>
    <th>
      Damper
    </th>
    
    <th>
      Function
    </th>
    
    <th>
      Typical position
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      <strong>
        Diverter damper
      </strong>
    </td>
    
    <td>
      Swings flow between two ducts
    </td>
    
    <td>
      HRSG bypass / GT exhaust diverter
    </td>
  </tr>
  
  <tr>
    <td>
      <strong>
        Louver damper
      </strong>
    </td>
    
    <td>
      Multiple parallel blades for throttling and partial isolation
    </td>
    
    <td>
      Flue-gas distribution, ID-fan modulation
    </td>
  </tr>
  
  <tr>
    <td>
      <strong>
        Guillotine damper
      </strong>
    </td>
    
    <td>
      Full isolation by sliding plate
    </td>
    
    <td>
      Boiler outlet isolation, baghouse compartment isolation
    </td>
  </tr>
</tbody>
</table>

## Damper-related failure modes

- **Sticking** — particulate accumulation in blade slots or guillotine guides prevents free movement
- **Seal failure** — eroded or compacted seals leak isolation-critical flow
- **Blade fouling** — distorts the designed flow pattern and creates uneven distribution
- **Slow stroke time** — fouled actuators or guides take longer to operate than design

## Sonic horns on damper areas

[Sonic horns](/glossary/sonic-horn) installed adjacent to damper assemblies help keep blade and seal areas clear of accumulating particulate, preserving stroke time and isolation integrity. This is particularly valuable on HRSG diverter dampers where slow stroke time delays plant start-up.

## Related terms

- [Heat Recovery Steam Generator (HRSG)](/glossary/heat-recovery-steam-generator)
- [Combined-cycle gas turbine (CCGT)](/glossary/combined-cycle-gas-turbine)
- [ID fan / FD fan / PA fan](/glossary/id-fan)
- [Sonic horn](/glossary/sonic-horn)