Glossary · Functional safety
Safety-related control system (SCS)
Also known as: SCS, SRECS, safety-related electrical control system
German: Sicherheitsbezogenes Steuerungssystem
In functional safety of machinery under IEC 62061, a safety-related control system (SCS) is the part of the control system of a machine that implements a safety function by means of one or more subsystems. Earlier editions used the term safety-related electrical control system (SRECS).
- Functional safety
- Systems engineering
In one sentence
A safety-related control system (SCS) is the part of a machine's control system that implements safety functions through subsystems.
Example
The SCS of a bending machine consists of a light curtain subsystem, a safety PLC subsystem and a hydraulic valve subsystem that together stop the ram when the protective field is interrupted.
How it applies
- Engineering: IEC 62061 structures each safety function into subsystems, typically input, logic and output, and determines the SIL for the function from the subsystems' failure measures and architectural constraints.
- Scope: IEC 62061:2021 extends the standard to non-electrical technologies, which is why the term SRECS was replaced.
- Verification: The SCS is verified against the safety requirements specification and validated on the machine.
- Documentation: Document each safety function with its subsystems, SIL, PFH and assumptions. The documentation team should keep the naming of functions and subsystems identical in calculations, circuit diagrams and the manual.
SCS vs. SRP/CS
Safety-related part of a control system (SRP/CS) is the ISO 13849-1 term. SCS is the IEC 62061 term. Both describe the safety-related control of machinery; the rating scale (PL or SIL) and methods differ.