Line Breaking — Why "Depressurised" Is Not "Safe to Open"
02:40, night shift. A DN150 condensate line off a boiler-feed pump discharge — 8 barg, 150 °C — has been weeping at a flanged joint for two days and maintenance finally has a window. The fitter has done what a careful person does. He shut the upstream gate valve. He cracked the 1″ drain and watched: nothing came out. He looked at the gauge on the isolated side: zero . He comes to you with the permit and says the sentence everybody says:
"It's depressurised and it's empty. It's safe to open."
Guess first, before reading on: how many separate…
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