Safety-related parts of control systems must be designed so that single fault in any of these parts does not lead to the loss of the safety function.²http://www.felcro.co.id
Whenever reasomably pravticable, the single fault shall be detected at or before the next demand upon the safety function. This does not mean that all faults will be detected. http://www.pilz.comThe accumulation of undetected faults can lead to an uninteded output signal and a hazardous situation at the machine. click http://www.pilz.de