Safety Instrumented Systems for the Process Industry Sector

The NBR IEC 61511-1 – Functional Safety – Safety Instrumented Systems for the Process Industry Sector – Part 1: Framework, Definitions, System, Hardware, and Application Programming Requirements presents the requirements for the specification, design, installation, operation, and maintenance of Safety Instrumented Systems (SIS). It ensures that the system reliably achieves or maintains the process in a safe state.

The NBR IEC 61511-1 was developed as the implementation of the IEC 61508:2010 series for the process sector. It specifies the requirements to achieve functional safety but does not specify who is responsible for implementing the requirements (e.g., engineering, suppliers, operating/owning company, builder).

Responsibility is assigned to different entities according to safety planning, project planning and management, and national regulation. It applies when devices that meet the requirements of the IEC 61508 series, published in 2010, or the IEC 61511-1:2016, 11.5, are integrated into the overall system, which is used in a process sector application.

It does not apply to manufacturers who wish to claim that their products are suitable for use in SIS for the process sector (see IEC 61508-2:2010 and IEC 61508-3:2010). It determines the relationship between ABNT NBR IEC 61511 and the IEC 61508 series. It applies when application programs are developed for systems that have limited variability language or when devices with fixed programming language are used.

However, it does not apply to manufacturers, designers, users, and integrators of SIS who develop embedded software (system software) or use full variability languages (see IEC 61508-3:2010). It applies to a wide variety of industries in the process sector, including the chemical, oil and gas, paper and pulp, pharmaceutical, food, and non-nuclear power generation industries.

It presents the relationship between SIF and other instrumented functions. It results in the identification of the functional requirements and safety integrity requirements of the SIF, taking into account the risk reduction obtained by other methods. It specifies the lifecycle requirements for system architecture and hardware configuration, application programming, and system integration.

It specifies the application programming requirements for SIS users and integrators. It applies when functional safety is achieved, using one or more SIF for the protection of people, public protection, or environmental protection. It can be applied to non-safety-oriented applications, such as asset protection.

It determines the requirements for the deployment of Safety Instrumented Functions (SIF) as part of the overall architecture to achieve functional safety. It uses the SIS safety lifecycle and specifies a list of activities necessary to determine the functional requirements and safety integrity requirements for the SIS.

It specifies that a hazard & risk assessment (H&RA) be carried out so that the safety functional requirements and safety integrity levels (SIL) for each SIF can be determined. It establishes numerical targets for the average probability of failure on demand (in demand mode) and the average frequency of dangerous failures (in demand and continuous mode) for each SIL.

It specifies the minimum requirements for hardware fault tolerance (HFT). It specifies the techniques and measures required to achieve the specified SIL. It determines a maximum level of functional safety performance (SIL 4) that can be achieved by an SIF that has been implemented in accordance with NBR IEC 61511-1.

It determines a minimum level of functional safety performance (SIL 1) below which NBR IEC 61511-1 does not apply. It presents a framework for establishing the SIL, but does not determine the SIL required for a specific application (which should be established based on knowledge of the particular application and the overall goal of risk reduction).

It specifies the requirements for all parts of the safety instrumented systems, from the sensor(s) to the final element(s). It determines the information that is necessary during the SIS safety lifecycle. It specifies that the design of an SIS considers human factors. It does not associate any direct requirement on the individual operator or maintainer.

In jurisdictions where governmental authorities (e.g., national, state, municipal) have established process safety design, process safety management, or other regulations, these take precedence over the requirements determined in the IEC 61511 series.