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Investigation of undesirable incident involving falling object on Stena Don

During preparation for start-up of drilling activities on the Åsgard field on Wednesday, 30 May 2007, a hydraulic tool weighing about 790 kg fell down on an unsecured area on the drill floor on board the Stena Don facility. The Petroleum Safety Authority Norway (PSA) has investigated the incident. Our investigation revealed both regulatory non-conformities and weaknesses in technical equipment and procedures.

The Casing Guide Head tool was stored about 5.5 meters above the drill floor and only secured by one chain in eye bolts. Eye bolts are not designed for use as a securing device.

The incident did not cause personal injury or major material damage. No persons were present on the drill floor when the incident took place. If the equipment had hit personnel, the outcome could have been fatal.

During the investigation we identified non-conformities and an improvement potential in the following systems/barriers which could have prevented the accident:

  • Technical solution (from the supplier).

  • Documentation (from the supplier).

  • Risk assessment of equipment that comes to the rig.

  • Work descriptions and procedures.

  • Supervision, inspections of the equipment.


The investigation also showed dependency between the various barriers where weakness in for example documentation from the supplier entails that procedures and work descriptions are not good enough.

The non-conformities are related to deficiencies on the part of the manufacturer of the drilling equipment (National Oilwell Varco) and the shipowner (Stena Drilling AS).

We have asked Stena Drilling AS (Stena) to provide an account of how the non-conformities and identified improvement items will be followed up.

We have also asked Stena for a plan as to how experiences from the incident will be communicated in the industry so that similar incidents can be avoided in the future.

Contact person in the Petroleum Safety Authority Norway:
Inger Anda, press spokesperson
Telephone: +47 970 54 064