IEC 61511—functional safety in the process industry: the prominence of validation and verification in the lifecycle of a safety instrumented system

Abstract

As the concept of risk management has gathered momentum in the oil and gas industry during the past decade, so to has the adoption of IEC 61511, the internationally recognised standard for functional safety in the process industry. IEC 61511 is a risk-based standard that uses the concept of an electrical/electronic/programmable electronic based control system to implement autonomous means of risk reduction against a pre-defined unwanted hazardous deviation in a process.

While IEC 61511 has been in existence for more than a decade, the correct understanding and implementation of the standard to derive an effective demonstrate of compliance is still debatable.

The standard follows a cradle-to-grave approach to the lifecycle of any safety instrumented system and, unlike other standards where cherry-picking of the requirements may be carried out, IEC 61511 necessitates a demonstration of compliance to all lifecycle phases and their associated requirements.

The author of this peer-reviewed paper is fully aware of how difficult-to-digest the subject is; therefore, this paper on the prominence of validation and verification is presented in a pictorial, unambiguous and easy-to-digest manner while paying particular attention to the requirements defined for validation and verification in the standard. The topic of validation and verification in the overall lifecycle of IEC 61511 will be covered by the following questions:

1. What is the difference between validation and verification in the context of IEC 61511?

2. What is the difference between verification against IEC 61511 and IEC 61508?

3. When should planning for validation and verification happen?

4. When should validation and verification be carried out?

5. What are the implications of not carrying out validation and verification?

6. How does validation and verification fit into the wider context of the IEC 61511 lifecycle?

7. What level of independence is required for validation and verification?

The paper will also attempt to provide a practical example of how to implement an effective validation and verification strategy into an overall Functional Safety Plan to give the reader a clearer understanding of the obligations toward demonstrating compliance.