Functional Safety - Protection Against Malfunction
Functional safety is part of the overall safety that depends on a system or equipment operating correctly in response to its inputs. Neither safety nor functional safety can be determined without considering the systems as a whole and the environment with which they interact.
The instrumented safety systems are not new. It has long been the practice to fit protective systems to industrial process plant where there is a potential threat to life or to the environment in the event of malfunction. These systems are independent of the normal process control, and take some action to render the plant safe in the event of a malfunction. Safety integrity level (SIL) provides a target to be achieved for such systems.
IEC 61508 is the basic functional safety publication which can be applied across all industries. It is titled “Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems (E/E/PE, or E/E/PES)”.
Industry wise standards under umbrella of IEC 61508:
ISO 26262 – Automotive | IEC 60601 – Medical Devices |
IEC 62061 – Machinery | EN 50126 – Railway Applications |
IEC 50156 – Furnaces | IEC 61513 – Nuclear Sector |
IEC 61511 - Process Industry | IEC 61800 -5-2 – Electric Drives |
In a nutshell, Safety Integrity Level (SIL) is measure of probability of failure of functional safety system. A safety integrity level refers to the reliability of an entire safety system, not to the individual risk reduction measures. In general terms, it is the required performance by a safety system or safety instrumented function
