Before revision: In order to function properly as isolation devices, the NFPA requires certain features in rotary airlock valves, including a 0.0079’’ clearance between the rotor and housing, specific materials of construction, and 8 or more rotor vanes.
After revision: In order to function properly as isolation devices, the NFPA requires certain features in rotary airlock valves, including a 0.0079’’ clearance between the rotor and housing, specific materials of construction, and eight or more rotor vanes.