Automatic test of safety specifications for PLC programs in the Oil and Gas Industry∗

The software of Programmable Logic Controllers (PLC) for Safety Instrumented Systems in the oil and gas industry is designed based on safety specifications that must be validated prior to deployment. This paper proposes a method for the automatic test of the Cause and Effect Matrix specifications on PLC systems. For such testing, the specifications are represented as a set of Petri net models that observe the controlled system behavior. The use of a formal model allows to systematically compose and translate the Petri Nets into a program that commands the PLC inputs and observes when the PLC outputs fail the safety specifications. A prototype tool has been developed to automatically perform the test of the Cause and Effect Matrix on a given PLC. A furnace project has been used to ascertain that the proposed method is easy to use and viable.