Polymerizing cargoes safety—TB/ALL.

(a) Common vapor headers for polymerizing cargoes must be constructed with adequate means to permit internal examination of vent headers. (b) Vapor piping systems and pressure-vacuum valves that are used for polymerizing cargoes must be inspected internally at least annually. (c) Pressure-vacuum valves and spill valves which are used for polymerizing cargoes must be tested for proper movement prior to each transfer.