This part explains the relevant principles of functional safety for communication with reference to the IEC 61508 series as well as IEC 61784-3 and others (see Figure 1), and specifies a safety communication layer based on the OPC Unified Architecture.
Figure 1 shows the relationship between this part and the relevant safety and OPC UA standards in an industrial environment. An arrow from Document A to Document B means “Document A is referenced in Document B”.
Figure 1 – Relationships of OPC UA Safety with other standards
OPC UA Safety does this in such a way that OPC UA can be used for applications requiring functional safety up to the Safety Integrity Level (SIL) 4.
The resulting SIL claim of a system depends on the way OPC UA Safety is implemented within this system. That means that if a certain SIL is desired, this part must be implemented on a device which fulfils the requirements for this SIL as described in IEC 61508. In particular, measures against random hardware failures and systematic errors (e.g. software defects) must be taken.
Table 1 – Implementation of OPC UA Safety
OPC UA Safety is intended for implementation in safety devices exclusively.
Simply implementing this specification in a standard device (i.e. a device not fulfilling the requirements of IEC 61508) is insufficient to qualify it as a safety device.
[RQ2.1] A safety device with OPC UA Safety shall fulfil the requirements of IEC 61508 (according the SIL-level as described) when used in live operation.
This part does not cover electrical safety and intrinsic safety aspects. Electrical safety relates to hazards such as electrical shock. Intrinsic safety relates to hazards associated with potentially explosive atmospheres.
This part defines mechanisms for the transmission of safety-relevant messages among participants within a network using OPC UA technology in accordance with the requirements of IEC 61508 series and IEC 61784-3 for functional safety. These mechanisms may be used in various industrial applications such as process control, manufacturing, automation, and machinery.
This part provides guidelines for both developers and assessors of compliant devices and systems.