Hardware Fault Tolerance

Levels of Hardware Fault Tolerance (HFT) are established in functional safety standards IEC 61508 and IEC 61511, as the ability of a component or subsystem to continue to be able to undertake the required safety instrumented function in the presence of one or more dangerous faults in hardware. A hardware fault tolerance of 1 means that there are, for example, two devices and the architecture is such that the dangerous failure of one of the two components or subsystems does not prevent the safety action from occurring. In other words, HFT allows a safety system to let the process continue even with a designated failure in the hardware.