Primary Containment

Primary containment is the equipment that holds process material: vessels, pipework, pumps, exchangers, tanks, valves, flanges, seals and hoses. Loss of primary containment is the initiating event for almost every major process accident, which makes containment integrity the single most important barrier on any process plant.

Why LOPC matters even when nothing else happens

Most releases do not ignite. That is a matter of ignition sources, wind, timing and luck rather than of control. A small release that dispersed harmlessly and a vapour cloud explosion can share an identical cause, so every release should be treated as a failure of the most important barrier, regardless of its outcome.

Where releases come from

• Flanged joints — the most numerous potential leak paths on any plant.
• Pump and compressor seals.
• Small-bore connections — instrument tappings, drains, vents, sample points. Disproportionately represented in incident data because they are numerous, poorly supported and vulnerable to vibration fatigue.
• Hoses and temporary connections.
• Corroded or eroded pipework, particularly at dead legs, low points and under insulation.
• Human intervention — opening the wrong line, incomplete isolation, reassembly errors.