Automated/manual system that stops cargo transfer in seconds when a high-level alarm, leak, or other unsafe condition is detected.
Regulatory detail & full definition
On gas carriers ESD-1 closes ship valves; ESD-2 also closes shore valves via the Ship/Shore Link. Activated by tank high-high level, manifold leak detection, manual buttons at strategic points (CCR, manifold, accommodation). Shut-down sequence is typically completed within 30 seconds to avoid pressure surge in cargo lines.