Updated guidelines for using ISA/IEC 61511 – Functional Safety

• May 31, 2020
• Standards

Summary

Following a week of web-based meetings in mid-May, the ISA84 standards committee, Instrumented Systems to Achieve Functional Safety in the Process Industries, is moving well ahead in developing and updating a comprehensive set of technical reports providing guidance and practical examples for the global process industries in applying the widely used ISA/IEC 61511-2018 standards, Functional Safety – Safety Instrumented Systems for the Process Industry Sector, Parts 1-3. Those ISA/IEC standards, the first version of which was completed by ISA84 in 1996, 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 has now completed an update to one of several technical reports on specific phases of the SIS life cycle. ISA-TR84.00.04-2020 Part 1, Guidelines for the Implementation of ANSI/ISA-61511-1-2018 (IEC 61511-1), provides an overview of the SIS life cycle with references to several annexes containing detailed guidance on key aspects of the safety life cycle, including: “grandfathering” existing SISs, operator-initiated functions, separation of the basic process control system (BPCS) and SIS, field device and logic solver selection, manual shutdown considerations, and design/installation considerations (for example, wiring, power, relationship to BPCS, common mode impacts, and fault tolerance).

Another ISA84 technical report in revision, ISA-TR84.00.02, Safety Integrity Level (SIL) Verification of Safety Instrumented Functions, serves as a tutorial on the fundamentals of data selection and the reliability calculations. The revision is now complete with the exception of an example on calculating the PFDavg of an automated block valve undergoing partial stroke testing. That example is being reviewed by the ISA96 committee, Valve Actuators. The revised technical report is expected to be completed by the end of this year.

This work follows the late 2019 publication of ISA-TR84.00.03, Automation Asset Integrity (AAI) of Safety Instrumented Systems, which presents guidance on establishing an effective AAI program that demonstrates through traceable and auditable documentation that the SIS and its equipment are maintained in an “as good as new” condition.

Previous ISA84 technical reports also 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. Input and collaboration between ISA84 and ISA99, Security for Industrial Automation and Control Systems, is ongoing as a new revision effort is now underway.
• 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, 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 revised by ISA84, with a focus on providing BMS-specific guidance/clarity to all phases of the safety life cycle, updating unit operation examples based upon the latest governing standards/practice (for example, NPFA 85, API 556), and updating based on end user feedback from the current edition.

Web meeting success

The web meetings in mid-May drew more than 90 attendees from across the globe during the main committee sessions and were well attended throughout the week. Based on that success, ISA84 is planning another week of web meetings to be held 12–15 October.

ISA standards participation and meetings are open to all interested parties, and experts from any country are welcome to join the ISA84 committee. For more information, contact Charley Robinson, ISA Standards, crobinson@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: crobinson@isa.org.

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