Recommend or Share:

Participate in the next training workshop on safety requirements specifications given by instructor Eng. Qco. Roberto E. Varela to learn how to develop and write the SRS of a safety instrumented system – SIS. This course is the result of decades of experience by functional safety experts in the process industry.

What is SRS?

SRS stands for Safety Requirements Specifications. This is one of the most important documents that must be developed as part of any project involving a Safety Instrumented System.

The SRS forms the design basis of the SIS and contains the detailed specifications of each Safety Instrumented Function (SIF) included in the SIS.

When is the document generated?

If we focus on the Safety Life Cycle (CVS) of IEC 61511 Part 1:2016, we see the separate and specific phase 3 in the CVS focused on the SRS. The task of developing the SRS (Clause 10) takes place after the PHA hazard and risk analysis (Clause 8) has been carried out and the different safety functions have been assigned to the different layers of LOPA protection (Clause 9). CVS Phase 3 is the time to specify exactly the details of each SIF. The primary output document for IEC 61511:2016 CVS Phase 3 is the SRS.

Why is SRS important?

If the SRS is incomplete or poorly done, the design engineer will not have clear direction on how to engineer the SIFs and will consequently do a poor job with it, or assume something they think is correct (as it was not clearly specified) and ultimately result in a SIS that will not meet the original intent. Worse, by the time the asset owner finds out about this, it will be quite late in the life cycle and can mean waste of time or money (especially both) because the design has to be reworked if it is discovered through a pre-loading functional safety assessment in the hazmat process.  or through a lack of response from the SIS to a demand of the process.

What does an SRS contain?

A safety requirements specification document will have many technical details and requirements answering many questions, such as:

• What is the Security Integrity Level of each SIF?
• What is the architecture of SIFs?
• Will there be any redundancy and/or voting logic?
• What will be the accuracy of the sensors and transmitters?
• How will a SIF be bypassed or override?
• Cybersecurity requirements for SIF.

There are many more questions and requirements than these. If you have application program developed with software embedded in the safety PLC, which is part of the SIS functionality, then there should also be an SRS program.

The IEC 61511 standard for safety instrumented systems in the process industry has details of what a safety requirements specification should contain.

The essential key points of an SRS include:

• Creating Systematic Operating Procedures
• The Basics for the Design, Installation and Assignment of SIS Loops
• PHA and LOPA Process Risk Analysis Documentation.
• Document the SIF ties to your SIL within the document.
• Detailed analysis of the functionality of each SIF
• Identifying the Foundations of the Architecture
• Thorough presentation of SIL level specifications
• Inclusion of detailed hardware specifications and application program specifications (if required).

Importance of SRS according to international standards

One of the main international functional safety standards such as IEC 61511 related to safety instrumented systems for application in the process industry requires the development of an SRS. This specification incorporates the results of hazard and operational analyses obtained during risk assessment and HAZOP/PHA/LOPA reviews.

The safety requirements within the SRS document must be precisely defined, involving the SIS and SIF specifications with their respective SILs.

The document will incorporate the information in a clear way, avoiding acronyms or abbreviations and common engineering jargon so that it is easy to understand for people who require the SRS for the design, engineering, validation, operation and maintenance of an SIS.

Conclusion

In conclusion, the SRS is a document created during the security lifecycle, and includes all documents resulting from the previous phases of the CVS detailed in IEC Clauses 61511 Part 1:2016. It documents the hazards to be avoided, the frequency of occurrence of those hazards, the consequences, and other integrity and risk reduction requirements that must be met. The SRS not only provides the guidelines for the design, but also provides details on the testing and maintenance procedures during the operational stage. In addition, it is responsible for protecting the integrity of the protection system associated with ongoing operational processes. One of the main benefits of an SRS is that it is not a one-time generated document, but rather a live working document that will reflect any changes or modifications made during the useful life of the SIS.

Why should I participate in the SRS Training Workshop?

Nowadays, a training course at SIS is required by the process industry worldwide. In recent times, a practical approach to the implementation and design of a SIS as a whole in accordance with the requirements of the process-specific functional safety standard IEC 61511:2016 has been requested. In addition, it is being requested to cover the need to teach a specific course to learn how to develop an SRS.

This SRS workshop is available through WiseCourses Academy and is delivered virtually.

Who is the SRS Training Workshop for?

This Workshop is open to any engineer, technician or professional who performs tasks related to Functional Safety and who wishes to have practical experience in the development of an SRS for SIS implementation projects in accordance with IEC 61511.

In particular, it is aimed at those who have responsibilities within the scope of IEC 61511:

• Process plant managers who have responsibility for the management of functional safety involving Safety Instrumented Systems.
• Control and instrumentation engineers, chemical engineers, mechanical engineers, electrical engineers who have responsibility for or have participated in exercises for the determination of SIL, specification, design, operation and maintenance of plant protection that use safety instrumented systems.

What’s included in the SRS Training Workshop

The SRS training workshop will cover the following topics:

• Review of Functional Safety Concepts
• Security Lifecycle Review and FSM
• Revision of IEC 61508 and IEC 61511 / ISA S84 requirements
• Safety Lifecycle
• Hardware SRS concepts
• Software SRS concepts
• SRS documentation to be generated
• Hands-on experience through examples of developing an SRS for a security function.

Course Duration

Two (2) classes of 3 hours each, on two successive days, at a time to be defined.

Course language:

Spanish and English.

Prior knowledge

Prior knowledge of Safety Instrumented Systems is required to attend the course, accredited by certificates of attendance at Functional Safety of Processes courses.

Certificates

• Certificate of attendance accrediting the key topics covered in the course.
• Attendees who wish to do so can take an exam for the certification of the knowledge acquired.

Study Material

A PDF copy of the course support material and an SRS Briefing prepared by the Instructor will be provided.

Recognitions:

All participants who meet the course requirements and successfully pass the final exam with a good grade will be awarded a Digital Badge. The digital Badge certifies that the participant has attended the PS12 training course and has completed the final evaluation test with a good score, verifying that said participant has assimilated the new knowledge.