The South African Bureau of Standards (SABS) has officially adopted the International Electrotechnical Commission’s (IEC’s ) 61511 functional safety standard – which is applicable to safety instrumented systems for the process industry sector – designating it SANS 61511.
This further entrenches IEC functional safety standards as best engineering practices in South Africa for the application of safety instrumented systems in hazardous processes, and is a significant step for the determination of the required safety integrity levels in such processes.
Going forward, SANS 61511 is the applicable standard for protection instrumented systems across process industries, such as petrochemicals refining and storage, biofuels, chemicals, pharmaceuticals, power generation, pulp and paper, and bulk fuels storage.
According to product certification and knowledge company exida South Africa (SA), SANS 61511 represents the formalisation of a standard that has underpinned the company’s core business focus since its inception in 2004. The company sits on the SABS mirror committee, where the standard was adopted.
exida SA MD Owen Tavener-Smith says the new standard fundamentally defines the safety targets of a plant through risk analysis, following which safety instrumented functions to meet those targets can then be designed. He adds that, if the initial risk analysis is poorly executed, incorrect safety targets are defined, which ultimately results in a flawed, inherently unsafe plant design and major cost wastage.
“The risk analysis needed to determine safety targets is a complex specialisation and requires a lot of skill, and the consequences of getting it wrong can be catastrophic,” says Tavener-Smith. He adds that the last three projects undertaken by exida SA all entailed correcting dangerously inaccurate process safety targets that were derived from poor-quality risk analyses.
He cites the example of a new combined-cycle gas turbine power plant. The main engineering contractor on the project quickly realised that the safety targets (safety integrity levels) they were provided with were implausible; in some cases, they were assigned to incorrect equipment and, in other cases, they were unrealistically high. When requested to re-evaluate the risk analysis, exida SA found that the methodology used was being incorrectly applied.
Tavener-Smith therefore says this is why the adoption of IEC 61511 is a “landmark moment for South Africa’s process industries”, as it will compel companies to implement enhanced levels of functional safety systems in their process designs.
“Our message is, basically: do not cut corners in functional safety; it can have catastrophic and extremely costly consequences. “By getting it right first time, companies can greatly enhance their safety, efficiency and profitability,” he concludes.