Iec 61511 Pdf Free Download -
Facunda Ganesh
Functional Safety for Safety Instrumented Systems (SIS) is for functional safety aspects for the process, oil & gas, and chemical industries according to IEC 61511. For engineers, professionals and specialists involved in safety instrumented systems, it is important to have the fundamental knowledge of functional safety and the requirements of the functional safety standard IEC 61511 in reference to the IEC 61508 standard.
IEC 61511 defines requirements regarding the application and implementation of safety instrumented systems (SIS) in the process industry. It describes functional safety (FS) requirements in process plants via a life cycle approach, from concept, through design, installation, operation, maintenance and decommissioning. Understanding and properly applying these regulations is essential not only for compliance, but, more importantly, for protecting people, assets and the environment as well.
It is important when risk analysis determines that a SIS is required, the required risk reduction becomes the performance target for the SIS. IEC 61511 establishes requirements for designing and managing SISs to achieve specified safety integrity levels (SIL), which are related to order of magnitude ranges of risk reduction. Performance verification of safety instrumented functions is demonstrated using calculation techniques to determine the probability of failure on demand and spurious trip rate and using key performance indicators for feedback from field operations.
IEC 61508, the foundation for IEC 61511, was first introduced in 2000. The IEC 61508 standard is a generic functional safety standard which can be applied to any kind of safety system if the safety system has elements based on electrical, electronic or programmable electronic (E/E/PE) technology. This does not mean that the whole safety system needs to be based on E/E/PE technology. The safety system is allowed to have elements based on other technologies like mechanical, electro-mechanical or even pneumatic elements. The IEC 61508 is a complete standard and it addresses requirements for achieving functional safety in the systems it covers.
When Safety Instrumented Systems (SIS) are required within an installation, the first step would be to document the requirements. This document is often called a Safety Requirement Specification (SRS). The IEC 61511 standard specifies the general requirements for a SRS. It is important that a SRS is clear, concise, complete and consistent.
The SRS should contain the functional and integrity requirements for each Safety Instrumented Function (SIF). The SRS can be seen as the main reference document after which the design, installation, validation and operation of the system must follow.
A SRS is a multidisciplinary document that can ultimately be used by the Instrument / Control Engineer to design a Safety Instrumented System.
PSM-covered facilities should execute the standard risk assessment process for fired equipment, like how they do for the other equipment in their facility, to determine if it should be included from a risk-based approach, in the PSM program. Gaps found through the risk assessment process may need to be closed through the application of ISA/IEC 61511. Further, OSHA considers ISA/IEC 61511 as RAGAGEP (Recognized and Generally Acceptable Good Engineering Practice) for safety instrumented systems (SIS). Integrating NFPA, ISA/IEC 61511, and PSM for fired equipment together may create a safer facility.
All three above-mentioned NFPA codes reference ISA/IEC 61511 as a recognized methodology for achieving equivalency. Likewise, OSHA recognizes ISA/IEC 61511 as RAGAGEP for SIS as part of PSM covered processes.
IEC 61511 has NO guidance on WHO is responsible for each SIS safety life-cycle activity. It's ultimately the hazard owner's duty to demonstrate adequate safety, and that cannot be fully transferred to 3rd parties. Management allocation of responsibility and accountability is a crucial aspect that the standards simply do not, and cannot define.
There are no specific procedures, techniques or methods that have to be dutifully followed in IEC 61511. This is great for flexibility, but makes it challening to demonstrate conformance and completeness.
Ther are no requirements in IEC 61511 for safety functions that are not instrumented (e.g. relief valves), or for other non-instrumented safety-related activities which may reduce risk. Other standards will apply to those.
IEC 61511 is not a means for manufacturers to make claims about SIL capability of their devices. Users can make "prior-use" claims according to IEC 61511, but that requires documented experience of real use and failure records over quite a long time period. IEC 61508 can provide manufacturers an alternative route for "proven-in-use".
IEC 61511 is not a means for manufacturers or others to make SIL claims about embedded software or applications with full variability languages - FVL (FVL includes C, C++ etc.). IEC 61508 is the reference source for embedded and FVL software.
This year, the process industry has reached an important milestone in process safety-the acceptance of an internationally recognized standard for safety instrumented systems (SIS). This standard, IEC 61511, documents good engineering practice for the assessment, design, operation, maintenance, and management of SISs. The foundation of the standard is established by several requirements in Part 1, Clauses 5-7, which cover the development of a management system aimed at ensuring that functional safety is achieved. The management system includes a quality assurance process for the entire SIS lifecycle, requiring the development of procedures, identification of resources and acquisition of tools. For maximum benefit, the deliverables and quality control checks required by the standard should be integrated into the capital project process, addressing safety, environmental, plant productivity, and asset protection. Industry has become inundated with a multitude of programs focusing on safety, quality, and cost performance. This paper introduces a protective management system, which builds upon the work process identified in IEC 61511. Typical capital project phases are integrated with the management system to yield one comprehensive program to efficiently manage process risk. Finally, the paper highlights areas where internal practices or guidelines should be developed to improve program performance and cost effectiveness.
Most process plants are controlled by complex process control systems; there is increasing dependence on safety instrumented systems (SISs) to carry out safety instrumented functions (SIFs).This technical publication focuses on quantitative and semi quantitative safety integrity level (SIL) determination techniques and supports practical application of the following clauses of IEC standard 61511-1:
Several standards have been enacted to address the reliability of SISs. ANSI/ISA S84.00.01-2004, Functional Safety: Safety Instrumented Systems for the Process Industry Sector, first issued in 1996, has now been harmonized with IEC 61511 issued in 2003. In March 2000, OSHA issued a letter, reaffirmed in November, 2005, stating that the S84 standard is considered "good engineering practice" for safety instrumented system design. This effectively makes the S84 standard part of process safety management (PSM) since paragraph (d)(3)(ii) of the OSHA PSM standard specifies: "The employer shall document that equipment complies with recognized and generally accepted good engineering practices".
IEC 61511 / ISA 84 identifies three Safety Integrity Levels (SILs) for the process industries and specifies performance requirements for each level. Different levels of risk require different levels of safety system performance.
This course teaches the important concepts and terms needed to understand the IEC 61511 / ISA 84 standard and it describes its requirements and its relationship to PSM. The detailed requirements for a Process Hazard and Risk Assessment (PHRA) and the allocation of safety functions to protection layers are discussed. A key requirement of IEC 61511 / ISA 84 is the development of a Safety Requirements Specification (SRS). The course explains how to prepare the SRS and attendees develop a SRS in a workshop session.
Understand the overall requirements of the IEC 61511 / ISA 84 standard for SIS. Understand the requirements for a PHRA and the allocation of safety functions and how they relate to PHA. Be able to prepare a SRS for each SIS.
BS EN 61511, Functional safety - Safety instrumented systems for the process industry sector, is the benchmark standard for the management of functional safety in the process industries. It defines the safety lifecycle and describes how functional safety should be managed throughout that lifecycle. It sets out many engineering and management requirements, however, the key principles of the safety lifecycle are to:
BS EN 61511 also defines requirements for management processes (plan, assess, verify, monitor and audit) and for the competence of people and organisations engaged in functional safety. An important management process is Functional Safety Assessment (FSA) which is used to make a judgement as to the functional safety and safety integrity achieved by the safety instrumented system.
The other day, a colleague stopped by my office to chat. We talked of the kids, our health, upcoming business travel, etc. The conversation eventually turned toward arcane points of IEC 61511 SIS engineering, as an alarming number of my conversations do. I expressed my controversial opinion in a haphazard way that I think impressed neither of us. This post is all the smart stuff I wish I had said in that conversation.
The data above is consistent with the philosophy of IEC 61511, which places great emphasis on the control of so-called systematic failures. However, the topic of systematic failures is a source of confusion in the functional safety community, in part because of the universally vague, frequently conflicting, and occasionally wrong guidance given in the standard. In this post, we will provide an overview of the topic, show how the standards may mislead users, and suggest an approach to how systematic failures should be treated.
582128177f