What is a SRPCS (functional safety)?

SRPCS just stands for Safety-Related Parts of Control Systems (sometimes also written SRP/CS).

Your control system might be split into a part that is safety-related (this is the SRPCS) and a part that is not safety-related. The safety-related part is responsible for ensuring that the machine operates safely, while the non-safety-related part handles regular operations.

The term originates in the EN ISO 13849-1 standard, which provides guidelines for designing and implementing safety-related control systems.

Source: Meister Automation, but can be found all over the internet.