Don’t lose your tow in heavy weather

Though primarily aimed at large drilling rigs, such as semi-submersibles, conical or other types of non-standard tows, it has broad application to all offshore engineering activities.

In late 2012, the Kulluk, a conical drilling unit, suffered a series of mishaps which ultimately caused the rig to run aground in Alaska. An investigation was conducted by the USCG and the associated Report of Investigation can be found at uscg.mil/hq/cg5/cg545/docs/documents/Kulluk.pdf. The National Transportation Safety Board also published a Marine Accident Brief on the incident – see ntsb.gov/investigations/AccidentReports/Reports/MAB1510.pdf.

In early August of this year, the Transocean Winter – a 17,000-ton semi-submersible drilling rig – went hard aground on the west side of the Isle of Lewis, Scotland. This incident is currently under investigation by the UK Maritime Accident Investigation Branch (MAIB). The USCG alert notes that it could have similar causal factors to the Alaskan incident.

One recommendation stemming from the USCG investigation on the Kulluk incident was the establishment of a workgroup to address the issues related to the towage of mobile offshore drilling units (MODUs) in high latitude environments. The workgroups final report was delivered to the Coast Guard during Q2 2016. The report provides valuable information for all organisations and professionals associated with towing large structures at sea, such as MODUs.