During the trans-spooling of an umbilical, a tensioner pad retaining bolt sheared, resulting in a 1.5kg tensioner pad dislodging and falling 11m to the under-deck carousel, where it struck the already trans-spooled umbilical. The dropped pad then bounced towards the starboard side, narrowly missing the deck supervisor, and landed on a salt sack approximately 1 metre from him.
What went wrong? What were the causes?
- A decision had been taken not to change the grade 8.8 bolts with the 10.9 bolts, due to resources, timescale and difficulty of access;
- The retaining bolt was not subject to an inspection, nor were the torque values checked due to the difficulty in accessing the tensioner;
- Risk assessments had not been conducted prior to the work activity, therefore there had been no consideration of potential dropped objects or mitigation thereof.
What actions were taken? What lessons were learned?
- Replace M10 x 25mm grade 8.8 retaining bolts with M10 x 25mm grade 10.9 on all equipment prior to mobilisation to vessels;
- Corrective work orders to be fully completed inclusive of inspection of tensioner pad retaining bolts and torque value checks, prior to mobilising equipment to vessels;
- Risk assessment of this type of work should take place before it starts.