Functional Safety

Functional Safety

Safety is not an option

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 the environment should something go wrong. 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 with a target to achieve for such systems.

IEC 61508 is 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.

Safety Integrity Level

Probability of failure on demand

Risk Reduction Factor


0.001% to 0.01%

100,000 to 10,000


0.01% to 0.1%

10,000 to 1,000


0.1% to 1%

1,000 to 100


1% to 10%

100 to 10

Functional Safety Services

We are looking forward to your enquiry