As the name implies, these are valves and as such provide isolation to much higher degree than dampers.
Where ducts carry noxious fumes and isolation is required to protect personnel downstream, only a valve offering total isolation will suffice.
This can be accomplished in one of two ways:
- Provide a damper system in such a way that purge air can be introduced at a higher pressure than the process gas, (see Louvre dampers), or
- Insert a blanking plate between two flanges or fit a Flowseal swing type Line Blind or a Flowseal fully automated Goggle Valve in the line.
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Where gas tight operation is required Two Lever Disc Valves, Double Offset, Butterfly or Knife Gate Valves provide an economical solution (however these valves cannot be considered as man-safe).
Materials of construction and drive configurations are selected and designed to suit the application and customer requirements.
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