Category Archives for "Process Industry Safety"

safety instrumented systems operation and maintenance

Process SIS Operations Blog #2

Operation and maintenance procedures for Safety Instrumented Systems (SIS) will vary from company to company. However, there are some specific requirements that need to be covered for safe continued operation.

The first blog on this topic discussed general operation and maintenance (O&M) requirements for sustaining the integrity of a SIS. This second article discusses the requirements for developing and maintaining SIS O&M procedures.

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safety instrumented systems operation and maintenance

Process SIS Operations Blog #1

How do you ensure a Safety Instrumented System in operation will maintain its original design integrity for a lifetime of 15+ years?

The IEC 61511 (2016) safety life-cycle provides some brief guidance for operation and maintenance of a safety instrumented system (SIS) in clause 16. The stated objectives are to ensure that the validated system’s safety integrity is not compromised in any way, and that the SIL for each safety instrumented function (SIF) is sustained over the whole system lifetime.

Once an SIS reaches the operation stage, it's important that equipment is regularly inspected and maintained. Proof test procedures should have been developed for each safety function. The frequency of carrying out these inspections and tests should already have been determined by probability of failure calculations.

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iec 61511 edition 2 standard for safety instrumented systems - eFunctionalSafety news

Update on IEC 61511 – edition 2

The process sector standard IEC 61511 is aimed at applications where instrumented systems are used for risk reduction in the process industry sector - including applications in chemicals, oil and gas, pulp and paper, pharmaceutical manufacturing, food and beverage, and non-nuclear power generation. Reduction of risk can be applied in the context of people, the environment and asset loss.

The original standard was published in the early 2000's, so edition 2 is a planned update. The intent of re-publishing it is to amend things that were not clear or simply were not working so well.

Due to the reference to sister standard IEC 61508 (2010 edition), suppliers of sensors, logic solvers and valves must seriously get to grips with updating any "SIL capability" certifications that pre-date 2010. All suppliers of devices with embedded software, operating systems and application programs must show evidence of product or system resilience to cyber-attacks.
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Ever wondered what LoPA is?

LoPA -Layer of Protection Analysis

Process facilities should be designed as far as possible to be inherently safe. Inherent safety involves reducing hazardous inventory and making the process mechanical design sufficiently robust.

However, it is not always possible to reduce risk to tolerable levels by inherent safety measures. Where further risk reduction is required, protection layers will be needed to prevent incidents propagating into accidents. Mitigation layers will be needed to minimise the consequences of hazardous failure events. LoPA provides special rules for protection layer credit which, when applied correctly, should ensure that adequate risk reduction is applied in the design.

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Safety life-cycle- adapted by eFunctionalSafety from IEC 61511

Why is there a safety life-cycle for automation systems?

The safety life-cycle, sometimes spelled lifecycle, was conceived after the Health and Safety Executive (HSE - a UK government agency) found that accidents involving control systems could be attributed to various different root causes.

The highest root cause of accidents was found to be poor specification of the system (44% of cases), followed by modification after commissioning (20%), and then poor operation or maintenance (15%). 

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