Division 1.2.1 Safety and reliability of control systems

Control systems must be designed and constructed in such a way as to prevent hazardous situations from arising. Above all, they must be designed and constructed in such a way that:

• they can withstand the intended operating stresses and external influences,

• a fault in the hardware or the software of the control system does not lead to hazardous situations,

• errors in the control system logic do not lead to hazardous situations,

• reasonably foreseeable human error during operation does not lead to hazardous situations.

Particular attention must be given to the following points:

• the machinery must not start unexpectedly,

• the parameters of the machinery must not change in an uncontrolled way, where such change may lead to hazardous situations,

• the machinery must not be prevented from stopping if the stop command has already been given,

• no moving part of the machinery or piece held by the machinery must fall or be ejected,

• automatic or manual stopping of the moving parts, whatever they may be, must be unimpeded,

• the protective devices must remain fully effective or give a stop command,

• the safety-related parts of the control system must apply in a coherent way to the whole of an assembly of machinery and/or partly completed machinery.

For cable-less control, an automatic stop must be activated when correct control signals are not received, including loss of communication.