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An SIS performs a safety instrumented function (SIF). The SIS is credited with a certain measure of reliability depending on its safety integrity level (SIL). The required SIL is determined from a quantitative process hazard analysis (PHA), such as a Layers of Protection Analysis (LOPA). The SIL requirements are verified during the design ...
I. van Beurden, W. Goble, "Safety Instrumented System Design-Techniques and Design Verification" (1st Edition ISBN 978-1-945541-43-8, 430 pages). M.J.M. Houtermans, "SIL and Functional Safety in a Nutshell" (Risknowlogy Best Practices, 1st Edition, eBook in PDF, ePub, and iBook format, 40 Pages) SIL and Functional Safety in a Nutshell - eBook ...
IEC 61511 provides good engineering practices for the application of safety instrumented systems in the process sector. In the United States ANSI/ISA 84.00.01-2004 was issued in September 2004. It primarily mirrors IEC 61511 in content with the exception that it contains a grandfathering clause:
A high-integrity pressure protection system (HIPPS) is a type of safety instrumented system (SIS) designed to prevent over-pressurization of a plant, such as a chemical plant or oil refinery. The HIPPS will shut off the source of the high pressure before the design pressure of the system is exceeded, thus preventing loss of containment through ...
These lead to such erroneous statements as the tautology "This system is a SIL N system because the process adopted during its development was the standard process for the development of a SIL N system", or use of the SIL concept out of context such as "This is a SIL 3 heat exchanger" or "This software is SIL 2". According to IEC 61508, the SIL ...
It covers alarms from all systems presented to the operator, which can include basic process control systems, annunciator panels, safety instrumented systems, fire and gas systems, and emergency response systems. The practices are applicable to continuous, batch, and discrete processes.
Although functionally separate, process control and shutdown systems are usually interfaced under one system, called an integrated control and safety system (ICSS). Shutdown systems typically use equipment that is SIL 2 certified as a minimum, whereas control systems can start with SIL 1. SIL applies to both hardware and software requirements ...
Layers of protection analysis (LOPA) is a technique for evaluating the hazards, risks and layers of protection associated with a system, such as a chemical process plant. . In terms of complexity and rigour LOPA lies between qualitative techniques such as hazard and operability studies (HAZOP) and quantitative techniques such as fault trees and event trees.