ISA84 approves IEC 61511, moves ahead on key supporting guidelines

ISA84, Instrumented Systems to Achieve Functional Safety in the Process Industries, has approved the newest edition of IEC 61511 as ISA and American National Standards Institute (ANSI) standards. The new standards will be designated in the U.S. as ANSI/ISA-61511, Functional Safety - Safety Instrumented Systems for the Process Industry Sector, Parts 1-3. The standards set forth requirements for the specification, design, installation, operation, and maintenance of a safety instrumented system (SIS) so that it can be entrusted to achieve or maintain a safe state of a process.

ISA84 developed the original ISA-84.01 standard on which the first edition of IEC 61511 was based. This new edition of IEC 61511, developed under IEC SC65A/MT 61511, was approved by ISA84 without modification-but not without concerns from several ISA84 members about the guidance and interpretation of IEC 61511-2, Part 2: Guidelines for the Application of IEC 61511-1. For that reason, ISA84 prepared a special foreword to ANSI/ISA-61511-2 that refers users to several ISA84 technical reports for guidance on the same topics. Those technical reports include:

  • ISA-TR84.00.09-2017, Cybersecurity Related to the Functional Safety Lifecycle, provides guidance on integrating the cybersecurity life cycle with the safety life cycle as they relate to safety controls, alarms, and interlocks, inclusive of safety instrumented systems. The scope includes the work processes and countermeasures used to reduce the risk involved due to cybersecurity threats to the industrial automation and control system network.
  • ISA-TR84.00.08-2017, Guidance for Application of Wireless Sensor Technology to Non-SIS Independent Protection Layers, addresses wireless technology-based sensors that are used in independent protection layers (IPL) providing a risk reduction factor of less than or equal to 10 (non-SIS IPL) by the authority having jurisdiction (typically the owner/operator or local regulatory authority), and establishes guidance and considerations for their utilization in the process sector.
  • ISA-TR84.00.07-2018, Guidance on the Evaluation of Fire, Combustible Gas and Toxic Gas System Effectiveness, is expected to be published in September 2018. It addresses detection and mitigation of fire, combustible gas, and toxic gas hazards in process areas. It clarifies information to be considered when developing a performance-based FGS design—including integrating the design activities into relevant portions of the safety life cycle model for safety-critical controls.
  • ISA-TR84.00.05-2009, Guidance on the Identification of Safety Instrumented Functions (SIF) in Burner Management Systems (BMS), is currently being updated by ISA84. It is intended to identify any SIFs within typical burner management systems for common operating modes of fired equipment (such as pre-firing, light-off, shutdown, and normal operation) and to provide examples of typical safety assessments for boilers (single burner), fired process heaters (multi-burner), thermal oxidizers, oil heater treaters, and glycol reboilers.

Three additional technical reports currently in development by ISA84 will provide guidance related to specific phases of the SIS life cycle:

  • ISA-TR84.00.02, Safety Integrity Level (SIL) Verification of Safety Instrumented Functions, will support the calculation of the average probability of failure on demand as required by ANSI/ISA-61511-1, providing guidance on (a) assessing random and systematic failures, failure modes, and failure rates; (b) understanding the impact of diagnostics and automation asset integrity activities on the SIL and reliability; (c) identifying sources of common cause, common mode, and systematic failures; and (d) using quantitative methodologies to verify the SIL and spurious trip rate.
  • ISA-TR84.00.03, Automation Asset Integrity (AAI) of Safety Instrumented Systems (SIS), will provide guidance on establishing an effective AAI program that demonstrates through traceable and auditable documentation that the SIS and its equipment are maintained in the "as good as new" condition.
  • ISA-TR84.00.04, Guidelines for the Implementation of ANSI/ISA-61511, will provide an overview of the SIS life cycle with references to annexes containing more detailed guidance on various subjects. It will also provide an end-user example of "how to" implement ANSI/ISA-61511.

Also of note

ISA84 and IEC will seek closer, more direct collaboration on future editions of IEC 61511 through establishment of an official liaison between ISA84 and IEC SC65A/MT 61511.

The next meeting of ISA will be 5-7 November 2018 at Wood (formerly Wood Group Mustang) in Houston. This will follow ISA's 2018 Process Control and Safety Symposium and Exhibition (PCS), also in Houston, on 30 October - 1 November (www.isa.org/pcs2018). Experts from any country are welcome to join the ISA84 committee by contacting standards@isa.org.

For information on viewing or obtaining the technical reports described above, visit www.isa.org/findstandards.

Have an idea for an ISA standard, book, training course, conference topic, or other product or service? Send it to idea@isa.org.

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