Case Study - Drop Tubes
FAA specifications for drop tubes required 2” 160 p.s.i. ASTM D-2239 polyethylene piping.
Polyethylene piping had not been tested as part of an assembly in fire tests. Therefore there was no UL classified firestopping system available.
Three manufacturers provided engineering judgements (EJ's) utilizing existing data for other non-metallic (plastic) piping, and provided data sheets for the use of their products with polyethylene piping.
The EJ's are based upon assemblies that were previously tested utilizing piping materials such as PVC, CPVC, ABS, and polybutylene.
All of the approved EJ's for drop tubes consist of an intumescent material to "choke off" the hole after the polyethylene material melts away during a fire. A metal collar is used to hold the intumescent material in place.
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