To understand the weaknesses of a control system and its potential for failure, a number of steps may be required. Each of these steps can be termed CHAZOP, although the term CHAZOP is most commonly applied to the second step:
A CHAZOP workshop study is a deep dive into the detailed workings of the control equipment, looking for any potential points of failure, especially single-point failure. Aspects to be considered include power supplies, hardware failure, software bugs, human factors, maintainability, non-normal operating conditions, and diagnostics, among others. In each case, the team asks the questions:
The CHAZOP report shows all the cases considered, and lists prioritized actions for improvement or further study.
In a recent CHAZOP study performed by the xSeriCon team, a client desired to perform a study to find vulnerabilities in the control system of a gas metering plant. The study was commissioned following a trip incident caused by a hardware maintainability problem, which led to shutdown of a gas-fired power station nearby.
The study found a number of unexpected issues for further investigation, including: