Hydrocarbon leak detection at cooling water outlets

[opo21]

Notes from Norman's book;
"Hydrocarbon leaks in water cooling service can cause explosive mixtures to form below
the distribution decks in cooling towers. Especially when cooling butane streams, this
can, and has (Amoco Oil—Texas City), caused cooling towers to ignite. Check your cooling
water outlets for combustible vapors perhaps once a month. The instrument that the
operators use to issue vessel entry permits can be employed for this purpose. Vapors tend
to accumulate beneath the distribution decks. Sludge buildup on these decks is another
indication and result of hydrocarbon leaks into the cooling water return."

We had this situation reported at least two times I remember from past year; detected reactively not through any proactive measures.
Should there be a check in place once a month?

[tuan]

We have already implemented automated cooling water return sample points / VOC analyzers (e.g., EPA Method 311 / El Paso Method) to have an early detection.
And that is the actual process safeguard that should be in place.

[jeem]

The context matters here: leaks into cooling water service are insidious because the vapors accumulate beneath the distribution decks rather than dissipate — they collect in a confined space where an ignition source eventually finds them, and Amoco's Texas City incident is a documented case where a butane-stream leak did exactly that. Monthly isn't arbitrary; it's tuned to catch accumulation trends before they reach an ignitable concentration.