HAZOP-Update, SIL-Verification for Compressor Station Legacy Systems




2017 – 2018

Key Project Data:

Existing gas transport compressor station, in operation since ca. 10 years, comprising:

  • Electric-motor-driven (EM) gas compressor
  • Gas-turbine-driven (GT) gas compressor
  • Pipeline interconnections, including metering stations
  • Tie-in of new pipeline and over-pressure protection systems (under construction 2018)
  • Existing station auxiliary and utility systems, including three independent legacy safety systems (Station, EM-compressor, GT-compressor)

Scope of Services:

  • Update of HRA (re-HAZOP) and SIL-analysis (Risk Graph method acc. VDI/VDE 2180)
  • Gap analysis of existing FSM-documentation
  • Preparation of Cause & Effect Chart for safety and process trip logic
  • Investigations on site to confirm as-built status of safety-related loops
  • SIL-Verification using ExSILentia and preparation of compliance report (equivalent to FSA-4) according to DIN EN 61511:2012
  • Preparation of recommendations and priorities for implementation

All services were carried out in accordance with PSC’s FSM-Plan as per DIN EN 61511 and CFSE-certified.

Extended Description

The following gives a detailed description of PSC‘s services.

Existing safety review was updated on basis of as-built status. The update was carried out via several workshops covering following nodes:

  • Station main process systems
  • Station auxiliary systems (vent, fuel gas, fire & gas system)
  • Flow path variations (ca. 50 station operating modes investigated)
  • Compressor-driver units, including auxiliaries
  • Tie-in of new pipeline and over-pressure protections

SIL / Risk reduction analysis carried out as per calibrated Risk Graph methodology (VDI/VDE 2180). 70 safety loops investigated, resulting in definition of SIL/RRF for 34 SIFs.

Review of legacy documentation established that some FSM-documents should be updated, e.g.

  • Cause & Effect Chart
  • Safety Requirements Specification
  • Sensor / actor failure data/ certification

Modelling of SIFs using ExSILentia software

  • Review of available E&I, safety system logic and vendor documentation and confirmation of ‘as-built’ status via site inspections
  • Database research / contact to manufacturers to establish failure data for legacy equipment with missing certification
  • Evaluation of ‘proven-in-use’ capability where published failure data was not available
  • Review of site proof-test procedures in order to define CPT for all SIFs
  • Modelling of loops in ExSILentia and preparation of compliance documentation
  • Recommendations based on identification of FSM-compliance issues:
    • SIL-degradation
    • End of equipment useful life
    • Proof test coverage
    • Management of non-SIL functions implemented in safety systems
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