This document specifies a safety communication layer (SCL) allowing safety-related devices to use the services of OPC UA for the safe exchange of safety-related data. A safety device that implements OPC UA Safety correctly will be able to exchange safety-related data and hereby fulfill the requirements of the international specifications IEC 61508 and IEC 61784-3. This document uses a monitoring number, a timeout, a set of IDs and a cyclic redundancy code for the detection of all possible communication errors which may happen in the underlying communication channel. These measures have been quantitatively evaluated and offer a probability of dangerous failure per hour (PFH) and a probability of dangerous failure on demand (PFD) sufficing to build safety related applications with a safety integrity level of up to SIL4.
OPC UA Safety itself is an application-independent, general solution. The length and structure of the data sent is defined by the safety application. However, application-dependent companion specifications (addressing for example electro-sensitive protective equipment, electric drives with safety functions, forming presses, robot safety, and automated guided vehicles) are expected to be defined by application-experts in appropriate OPC UA companion specifications.