Emergency Shutdown System (ESD)

Process Shutdown System (PSD)

Introduction on the safety system :

In offshore oil and gas facilities, safety systems are critical for preventing accidents and protecting personnel, equipment, and the environment.

Two of the most important systems are the Emergency Shutdown System (ESD) and the Process Shutdown System (PSD).

Although they are related, they serve distinct purposes and operate at different levels of safety and control.

Emergency Shutdown Engineering Process Shutdown Engineering Fire&Gas Engineering

Role of our Engineering Consultants in ESD/PSD Design

1. Initial Feasibility & Risk Analysis

  • Participate in HAZID / HAZOP workshops to identify potential hazards.
  • Contribute to risk assessments (e.g., Layer of Protection Analysis – LOPA).
  • Determine where safety instrumented functions (SIFs) are needed.
  • Help define whether a scenario requires a PSD action or ESD function.
  • Align risk reduction requirements with client safety philosophy.

2. Safety Requirements Specification (SRS) Development

  • Draft the Safety Requirements Specification per IEC 61511, including:
  • Description of each SIF (function, trigger, response)
  • Required SIL (Safety Integrity Level)
  • Process conditions (setpoints, delays, reset logic)
  • Diagnostic coverage, response times, and proof test intervals
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3. ESD/PSD System Architecture Design

  • Design the shutdown system architecture, including:
  • Input devices (pressure, level, fire/gas detectors)
  • Logic solvers (SIL-rated PLCs like Triconex, HIMA, ABB, etc.)
  • Final elements (ESD valves, blowdown valves, pump trips)
  • Define redundancy and voting logic (e.g., 2oo3, 1oo2 configurations)
  • Ensure fail-safe design philosophy is met (e.g., valves fail closed or open)
  • Create Cause & Effect Matrices (CEMs) showing trigger-response relationships

4. System Integration & Interface Design

  • Interface ESD/PSD systems with:
  • Fire & Gas System (FGS)
  • Distributed Control System (DCS)
  • Blowdown systems
  • Electrical isolation and emergency power
  • Define communication protocols (e.g., Modbus, Profibus, hardwired I/O)
  • Address human-machine interface (HMI) and alarm presentation

5. Regulatory & Standards Compliance

  • Ensure system design aligns with:
  • IEC 61511 – Functional safety lifecycle
  • IEC 61508 – Safety lifecycle for hardware/software
  • API RP 14C – Offshore safety system guidelines
  • Client and regional regulations
  • Support preparation of Functional Safety Assessments (FSAs)

6. Documentation & Deliverables

  • Consultants are responsible for generating and reviewing engineering documents such as:
  • Safety Requirements Specification (SRS)
  • Shutdown Philosophy Document
  • Cause & Effect Diagrams (C&E)
  • Logic Diagrams / Functional Block Diagrams
  • Instrument Loop Diagrams (ILDs)
  • Control Narratives
  • System Architecture Drawings
  • SIL Verification Reports (e.g., using tools like exSILentia, SILcet)

7. Installation, Commissioning & Validation Support

  • Assist in Factory Acceptance Testing (FAT) of SIS panels
  • Witness or conduct Site Acceptance Testing (SAT)
  • Perform loop checks and verify safety instrumented functions
  • Support Proof Testing procedures and validation of SIL achievement
  • Ensure Separation of ESD/PSD wiring from standard I/O as per safety class

8. Lifecycle Management & Maintenance Planning

  • Develop strategies for proof testing, bypass handling, and SIF maintenance
  • Create or review procedures for modification management
  • Ensure documentation supports functional safety audits
  • Train operations staff on ESD/PSD system use and alarms

Skills & Tools We Use

Technical Knowledge:

  • Functional safety design (IEC 61511/61508)
  • Process control and instrumentation
  • Offshore platform design and process flow
  • Valve actuation and fail-safe mechanisms
  • Alarm and interlock systems

Tools:

  • SIL verification software (e.g., exSILentia, PHAWorks, SIFPro)
  • CAD or E&I drawing tools (AutoCAD, SmartPlant Instrumentation)
  • Logic development tools (e.g., Triconex TriStation, HIMA ELOP II)
  • PLC programming and DCS interface design

Our Role in ESD/PSD Design:

Concept / FEED: Hazard analysis, draft safety requirements

Detailed Design: Develop C&E matrix, select hardware, verify SIL, I/O lists

Procurement: Specify SIS panels, final elements

Construction: Installation guidance, interface checks

Commissioning: Commissioning Procedures, SAT, loop testing, logic validation, Dynamic tests and Plant total black out and black start tests

Operation: Support proof testing, bypass procedures, updates

Decommissioning: Ensure safe SIF removal, documentation closure