How to classify failures when collecting data for safety-instrumented systems in the oil and gas industry

The oil and gas industry places a high value on achieving high reliability and availability on safety critical equipment. To achieve this, assessments of the reliability performances of such equipment are required, both before and during the production phase. The fact that the reliability data available to support the assessments is often sparse or insufficiently detailed presents a challenge. These assessments also typically require insights into the system in which the equipment is used and information about failure detection. However, this ensemble information is often difficult to achieve in the way the data are collected today. As a response to this challenge, one suggested option is to collect reliability data using one acknowledged failure mode classification specifically designed to assess the reliability of safety-instrumented systems. This is a classification adopted from the International Electrotechnical Commission standard 61508. In this article, we discuss the pros and cons of adopting this failure mode classification in generic reliability data collection in the oil and gas industry. One argument discussed is that the data may lack relevant information about the associated safety system and thus be valid for a specific system only, not for generic equipment and systems in general. Hence, should the classification be implemented, the collected data should be used with care.