Drilling rigs and units are very compact and complex structures, with significant inherent safety risks including potentially explosive atmospheres. The identification and management of hazardous areas is essential to safety on these vessels. Due to the age of the Stena Clyde, and a succession of owners, Stena Drilling did not have complete hazardous area classification documentation for the vessel. It sought assistance to conduct a re-classification of hazardous areas on the rig.

Stena Drilling did not desire a blanket-type hazardous area classification, which is a straightforward classification. Instead, it required individual areas within the vessel to be reviewed and classified appropriately. Consequently, the hazardous area classification relied upon a very careful, systematic understanding of the interrelationship between processes and potential hazards.

Drilling rigs and units are movable structures and rarely stay at the same location for long periods of time. Consequently, the classification had to consider variable environmental conditions, such as temperature and solar radiation, as well as differing regulations in the anticipated geographical locations in which the drilling rig may operate.

The method to undertake a hazardous area classification is usually fairly streamlined. However in this instance, the application of standard guidelines to classify hazardous areas was challenged by the hierarchical constraints of varying international and industry-specific regulations and guidelines.

Given the immediate operation of the rig within Australia maritime waters, Stena deferred to an Australian company to provide a hazardous area classification. It required the study to be completed within a tight timeframe, in order to obtain necessary contract work permits.

A hands-on practical approach offered the most effective way to identify and assess all 50 hazardous locations on-board the Stena Clyde. Consultation with the client proved invaluable as its operational experiences provided insightful evidence of emission sources and frequency. These characteristics are a crucial input into hazardous area classification and accompanying drawings.

Working closely with the client post site visit, the report and drawings were completed in a timely fashion and within budget. The result of our work was a document that Stena Clyde could confidently use as a reference document for the specification and design of electrical equipment within hazardous areas.