Apply Double Isolation

Image © EPSC


Spill of (hazardous) material can occur when a barrier (like a valve) fails and no second barrier is in place.

When Important

During routine and special operations: draining & sampling, (un-)loading activities, utility connections.

Challenges in the Field

  • Older plant design often do not provide a double barrier.
  • Blind flanges not put back after maintenance work.
  • Blind flanges not installed with bolts & missing end-caps.
  • Importance of “primary containment” not understood.
  • Valve handles that can be opened accidentally.

Options to Get it Right

  • Do not rely on a single valve for positive isolation.
  • Execute regular audits to check that drains are having an end-cap (blind flange or screw cap) conform pipe-spec.
  • Do not accept missing blind flanges or missing bolts on blind flanges.
  • Report and investigate all incidents from leaking drains.
  • Valve handles can be locked to avoid accidentally opening.

This page only summarises the guidance – refer to the EPSC website for further information.

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