schmersal PSC1 - Specification of the Functional Safety System; Definition of the Safety Functions

Installation manual
HB-37420-810-01-25F-EN PSC1-C-100 Installation manual - V2.2.docx Page 179 of 201
Version: 38F
12.3.3 Specification of the functional safety system
Derived from the general hazard and risk analysis for the machine, the active protection
functions are to be identified and specified.
Active protection functions are, e.g. safely limited speed in certain system states, monitored
stop and standstill functions, range monitoring, processing of monitoring devices such as light
grids, safety mats, etc.
The safety functions are each to be bounded and the specific requirements defined in relation
to function and safety level.
12.3.3.1 Definition of the safety functions
The definition of the safety function must:
• State the risk to be covered
• Describe the exact function
• List all sensors, controls involved
• Identify all controllers
• Identify the related shutdown circuit
• The definition is intended to form the basis for the specification of the hardware and
software design.
• For each of the safety functions defined in this manner, any parameters to be used,
e.g. max. system speed in the setting up mode etc. are to be defined.
• Example for safety functions:
o SF1: STO (safe torque off) for protection against safe startup
o SF2: Safe speeds
o SF3: Safe positions
o SF4.:……