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Chemical Engineering vocabulary · Process Safety and Hazards

Purge

Meaning in chemical engineering, with examples

/pɜːrdʒ/verbCommon term

In chemical engineering, purge means: To clear a vessel or pipe of air, flammable gas or toxic material by flushing it with an inert gas such as nitrogen, or with steam, before opening it or starting it up.

In Turkish: süpürmek, inert gazla temizlemek, pürj etmek

How it is used

Used in start-up, shutdown and maintenance procedures. Operators purge with nitrogen until oxygen is below a set limit before introducing hydrocarbons, and purge hydrocarbons out before handing equipment to maintenance. Also a noun: 'nitrogen purge', 'purge stream'.

Example sentences

  1. Purge the reactor with nitrogen until oxygen is below 2%, then start the hydrogen.

  2. The line was purged and gas-tested before the welders started work.

Common collocations

  • nitrogen purge
  • purge with nitrogen
  • purge the line
  • purge stream
  • steam purge
  • lower explosive limitThe lowest concentration of a flammable gas or vapor in air that can burn or explode if ignited. Below it, the mixture is too lean to burn.
  • start-upThe process of bringing a unit or plant from a shut-down state to normal operating conditions, following a written procedure step by step.
  • lockout/tagoutA safety procedure that isolates equipment from all energy sources and locks and labels the isolation points, so nobody can start it while people are working on it.
  • recycle streamA stream that takes unreacted material or a process fluid from a later point in the process and sends it back to an earlier point, so that it is not wasted.

More terms: Process Safety and Hazards

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