AS-Interface | The System | Safety at Work | Basics

Safety categories

Category	Summary of the requirements	System behaviour	Principle
B	The controls must be so designed that they can withstand the expected influences	A fault can lead to the loss of a safety function	Mainly characterised by the selection of components
1	The requirements of B must be fulfilled; use of tried and tested safety components and principles	As for B, but with higher safety-related reliability	Mainly characterised by the selection of components
2	The requirements of 1 must be fulfilled; additional testing of the safety function at suitable intervals	A fault is recognised at the next check	Mainly characterised by the structure of the controls
3	The requirements of 1 must be fulfilled; a single fault must not lead to the loss of the safety function	When a single fault occurs, the safety function remains intact
4	The requirements of 3 must be fulfilled; the single fault must be recognised before or at the next demand on the safety function	When faults occur the safety function remains intact. The faults are recognised

S - Severity of the injury	F - Frequency and duration	P - Possibility of avoiding the hazard
S1 - slight injury	F1 - seldom to often and/or short duration	P1 - possible under certain conditions
S2 - severe irreversible injury to one or more persons or the death of a person	F2 - often to continuously and/or long duration	P2 - scarcely possible

Shutdown by immediately switching off the energy supply to the machine drives (uncontrolled shutdown).

Controlled shutdown, whereby the energy to the machine drives is only switched off when the machine has come to a standstill

Controlled shutdown, where the energy supply is still fed to the machine drives (not permitted for Emergency Stop function)