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Fail-safe is a design concept to ensure that in case of equipment or system failure it will go to safe position to ensure people, equipment and enviroment safety.
A fail-safe in engineering is a design feature or practice that in the event of a specific type of failure, inherently responds in a way that will cause no or minimal harm to other equipment, the environment or to people.
A system's being "fail-safe" means not that failure is impossible or improbable, but rather that the system's design prevents or mitigates unsafe consequences of the system's failure. That is, if and when a "fail-safe" system "fails", it is "safe" or at least no less safe than when it was operating correctly.
A fail-safe in engineering is a design feature or practice that in the event of a specific type of failure inherently responds in a way that will cause no or minimal harm to other equipment, the environment or to people
causing a piece of machinery to revert to a safe condition in the event of a breakdown or malfunction.
In the field of Instrumentation & Control, Fail Safe refers to a configuration of “predefined operation” of control loop during a failure. It can be configured as a function of a final control element or a controller setting.
Example: Configuration on final Control Element.
If a Control Valve lose manipulated signal from controller (due to wire brake, controller failure or any other reason) to set a calculated position, fail safe setting will direct it immediately to set a pre-defined Fail safe position such as full open, full close, hold last value or nay other specific position depends on Plat and Personal safety requirements. Many final control elements have ability to actuate to its fail safe position even during power supply failure (by a spring stored energy). Sometimes fail safe position is fixed by manufacturer.
Example 2: Configuration on Controller.
If process variable or feedback signaling element of a control loop is fail due to any reason then controller is configured to generate a fixed valve of manipulated variable for positioning (fail safe) a final control element.
A system or plan that comes into operation in the event of something going wrong or that is in place to prevent such an occurrence. Or causing a piece of machinery to revert to a safe condition in the event of a breakdown or malfunction
