Vapour return line

A vapour return line is the cargo-vapour piping that connects a tanker’s cargo tanks to a shore vapour-recovery manifold so that hydrocarbon vapours displaced during loading return to the terminal instead of venting to atmosphere. It is the ship side of a vapour emission control system (VECS). The arrangement is mandatory for tankers loading at US ports under USCG rules and is required for crude oil tankers under MARPOL Annex VI Regulation 15, which obliges a crude tanker to carry and implement an approved VOC Management Plan per IMO Resolution MEPC.185(59). The line uses dedicated couplings, flame screens, and high/low-pressure protection to stay within the safe ullage-pressure envelope.