Flange / Gasket Weep — Detect & Isolate Early

A flanged or gasketed joint on a pressurised hydrocarbon line starts to weep from a bad gasket, under-torqued bolt, thermal cycling, or vibration. Small at first, it grows into a vapour source next to live equipment if nobody blocks it in.

Flanges, gaskets, and small-bore connections are consistently among the most common LOPC sources; minor releases are the leading indicators of major ones (this is exactly why API RP 754 tracks LOPC tiers). Every disaster in this genre started as a containment breach that wasn't stopped early.

1. Detect the rising leak early — gas-detector uptick, visual weep, cautious use of senses.
2. Identify the exact leaking segment and its isolation boundary.
3. Block in the segment (close isolation valves both sides).
4. Depressure/vent the trapped inventory to a safe path.
5. Keep ignition sources clear and escalate per procedure.

Common — the highest-frequency event family in the genre. IOGP member companies reported 193 Tier 1 and 622 Tier 2 process safety events (essentially LOPC) in 2021 alone — Tier 1 rate 0.12 per million work hours across ~1,655 million work hours (IOGP Safety…

Ignored, a weep grows into a flammable cloud beside live equipment — the common origin of the rupture/fire/VCE scenarios that follow (API RP 754 LOPC-tier logic; source doc Scenarios 2–9). Caught early it is a block-in and a gasket change.