Process Safety Lifecycle IEC61511 / IEC-61511

Are you also convinced that a plant will only become truly safer if you make invisible process safety risks visible, and that you can then take targeted action to reduce these risks? That you will achieve this if you go through all the phases of the process safety lifecycle described in the directive IEC 61511 Functional safety - Safety instrumented systems for the process industry sector? And that you are then also compliant with the BRZO legislation?

Process safety is about preventing incidents in which uncontrolled energy or product is released from the installation (LOC, loss of containment). The impact of a LOC is often great and can have consequences for people, the environment or the process installation itself. To start with, it is important to have a good process safety management system in place that consciously deals with process safety risks. The risk based process safety management principles of the Center for Chemical Process Safety (CCPS) are a good starting point:

  1. Commitment to Process Safety

  2. Understanding and recognising process safety risks

  3. Managing risks

  4. Learning from incidents


In 1995, the British Health and Safety Executive (HSE) published a report in which they investigated the causes of various process safety incidents and accidents at work resulting from the failure of control/automation systems.

This study provided insight into where and with what frequency errors occur in the process from design to maintenance of safety systems. And just as with our vision of "making invisible risks visible so that you can take targeted action to reduce them", making these errors visible led to the realisation that your plant will only become safer if you take account of safety in all phases of a plant's life: the (process) safety lifecycle. This in turn led to the international standard IEC 61511 for Functional Safety in which this is laid down.

And that is why we embrace the principles of the safety lifecycle and the related standard and have made them our mission. Focusing on all phases of the process safety lifecycle. The life cycle is divided into three main phases:

1 - Definition phase

Here, risks are analysed and assessed. The focus is on reducing errors caused by incorrect specifications. We do this through quantitative risk analyses(QRAs), safety studies(PHA) and risk reduction techniques(LOPA) that result in a correct specification of the safety systems (SRS).

2 - Implementation phase

In this phase, the focus is on minimising errors in the design and commissioning of the safety systems. You do this by designing procedures, alarms, mechanical protections and control system (DCS) interlocks. If necessary, this phase also includes the design of the Safety Shutdown Systems and the associated design documents such as SIL calculations and verifications, SIF designs, Safety Requirement Specifications (SRS), Cause & Effect diagrams and test procedures.

3 - Operational and maintenance (O&M) phase

In this phase, the focus is on minimising risks during operation and maintenance of the safety systems in the plant. This involves keeping track of and recording how often sensors, transmitters and valves in the safety system are invoked, how often errors occur, how often overrides are used and how often the system is tested. All these data are assumed in the definition (study) phase. In the O&M phase, you determine how good your assumptions in the study phase have been. In this phase you also need to establish how you will deal with changes to Safety Shutdown Systems after they have been put into operation for the first time (Management of Change; MOC).

In practice, this is a (labour) intensive task that is virtually impossible without the help of software designed for this purpose. We work with aeShield® to make digital transformation of the IEC 61511 Lifecycle a reality.

To learn more about aeShield®, click here.


"Holding on to a railing has never prevented an explosion"

- – Enrico Lammers