The importance of assessing the impact of change on safety related systems

Should all changes made to a SIS be subject to a formal Impact Assessment Process? If so, why and how will this be beneficial?

Functional safety (FS) impact assessments are vital to determine the potential risk any operational change may have on a safety related system. However, pressures stemming from lean management and budget constraints may result in some solutions not being adequately tested, which can compromise overall operational safety.

It is often said that change is good, finding new ways to deliver improvements through thinking and doing things differently.

In the industrial world, most companies have a strict regime in place to help ensure that new measures and procedures are properly and smoothly implemented and communicated as necessary. When it comes to operational safety, however, there is a risk that the impact of any changes may be paid limited attention, particularly where there is a focus on finding ways to reduce operating budgets.

There is also a common misconception that not all changes proposed for a safety related system need to be analysed for their impact and that only those changes that are ‘perceived’ to have a direct influence on the system really need to be impact assessed.

In fact, before implementing any changes to a safety related system, a functional safety impact assessment should always be performed to evaluate the safety of any proposed changes and investigate the risk of potential failure.

Why is a functional safety impact assessment necessary?

Those organisations that follow a functional safety management (FSM) system process must perform FS impact assessments regularly whenever any changes are made to a safety related system.  When any FS impact assessment is carried out, it is vital for engineers not to undervalue the importance it can have when delivering overall functional safety assurance.

Ultimately, FS impact assessments help to determine the impact a change to a safety function may have on other functions within a safety related system and its effect on risk reduction.

What do we mean by formal records of FS impact assessment?

Any FS impact assessment performed for any change will need to be formally recorded.  This is to ensure and demonstrate that a systematic process has been followed and that there is evidence of what was considered for the assessment.  In addition, all documents and the assessment result should be recorded to provide traceability.  By doing this, supporting evidence necessary for traceability can be demonstrated to interested stakeholders.

What changes are to be impact assessed for Functional Safety?

Any changes to any part of a safety system and/or critical interface need to be impact assessed. The FS impact assessment process should also be used on a broader basis to sustain operational requirements.  For example, any changes attributed due to failure of a proof test within the safety related system should also be handled by the change management and FS impact assessment practices before the corrective action is implemented and the solution re-verified.

Who should undertake and approve the FS impact assessment?

In accordance with the recommendations identified in the relevant safety standards, a competent person and/or team should perform the FS impact assessment for the proposed changes and document their findings in a structured report.  The report will then need to be reviewed and approved by another competent and independent person(s), ensuring a robust and systematic review has taken place, which can support the original findings.

So, how are changes to a Safety Related System being handled within your organisation? Have all changes been subject to an FS impact assessment? Are there formal records produced for these FS impact assessments? Can you readily demonstrate your findings to both internal and external stakeholders?  For further information see

Contact me at if you want to talk through how ABB can help you with changes to your Safety Related System

Categories and Tags
About the author

Suresh Sugavanam

I have over 19 years of experience in the provision of ABB Functional Safety Consultancy and SIS Project Execution for the Process Industries. I have held several high-profile management roles and responsibilities for SIS project and execution delivery in a number of differing manufacturing sectors for both Invensys and ABB. In my current role of Senior Functional Safety Consultant within the ABB Functional Safety Management Technical Authority (FSM TA), I provide FS consultancy solutions to ABB customers worldwide in addition to supporting the ABB Safety Execution Centres in implementing a robust Functional Safety Management System. I am a Member of the Institution of Engineering and Technology (IET), a member of ‘The 61508 Association’ and a TUV Rheinland certificated Functional Safety Expert.
Comment on this article