A HAZOP systematically reviews each section of a process to find deviations — more flow, less pressure, reverse flow — and checks that safeguards are adequate. SIL assessment then decides how reliable each safety instrumented function must be.

Key takeaways
  • Run HAZOP on mature P&IDs, not early drafts.
  • Use SIL assessment to size safety instrumented functions to IEC 61511.
  • Track every action to close-out before design freeze.

Why in FEED?

Changes found at HAZOP are cheap to make while the design is still on paper. Found during detail engineering or construction, the same change can affect equipment orders, layouts and schedules.

Running an effective HAZOP

  • An independent, experienced chairperson
  • Process, operations, instrumentation and safety in the room
  • Up-to-date P&IDs, cause and effect charts and operating philosophy
  • A clear action register with owners and due dates

From SIL to design

Each safety instrumented function gets a target SIL. This drives the choice of sensors, logic solver and final elements, proof test intervals and the safety requirement specification used by the control system vendor.