May, 2008 - PIPELINE SAFETY: Polyamide-11 (PA-11) Plastic Pipe Design Pressures. PHMSA proposes to revise the Federal pipeline safety regulations to allow certain thermoplastic pipelines made from new Polyamide-11 (PA-11) pipe to be designed using a higher design factor and to raise the design pressure limit for the same pipelines. Design pressure calculations and design pressure limitations for all other thermoplastic pipes (PE-polyethylene, PB-polybutylene, PVC-polyvinyl chloride, etc.) would remain unchanged. These rule changes would allow pipeline operators to operate certain pipelines constructed of new PA- 11 pipe at higher operating pressures than currently allowed by the existing rules.