What is the difference between a fault and a failure?
A fault is a state of a functional unit characterised by the incapability to perform a required function, with the exception of incapability during preventative maintenance or other planned activities or due to the lack of external materials. A fault is often the result of failure of the unit itself. Failure is the termination of the capability of a functional unit to fulfil a required function. Following a failure, the unit will have a fault. The “failure” is the event, in contrast to the “fault” which is a state. A further distinction must be made between: hazardous failure, which is a failure which has the potential to place a safety-related part of a control system into a state of hazard or malfunction; common cause failure (CCF): failures of different units due to a single event, where these failures are not interdependent; systematic failure: failure with a deterministic relationship to a particular cause which can only be eliminated by changing the design, the manufacturing proc
