Challenge
During a scheduled extended dry dock refit in Brisbane, Queensland, issues were discovered in the 3.2-meter-long stern tubes, which house the propeller shafts. Due to Ethereal's unique drive mechanism design, the initial inspection revealed significant marine growth buildup on the internal surfaces of the tubes. The prolonged periods of inactivity had allowed marine growth to propagate unchecked. Initial cleaning operations uncovered substantial pitting along the length and circumference of both the port and starboard tubes. Conventional NDT methods failed due to the vessel's thick walls, necessitating a more advanced approach to assess the condition of the tubes.
Solution
Inspectahire was engaged to provide consultancy and specialised services to ascertain the condition of the stern tubes. Utilising stereoscopic measurement technology and bespoke deployment techniques, Inspectahire's trained technicians employed the Olympus IPEX Videoprobe with a Stereo Optical Adapter tip to investigate pit locations. This advanced technology, which uses parallax-based stereoscopic measurement, allowed for precise assessment of pit width, depth, and area.
Inspectahire's technicians, skilled in both standard video scope operation and stereoscopic measurement, conducted a comprehensive survey of both tubes. The data provided detailed measurements of the pits, enabling accurate calculations of the remaining material and overall condition.
Results
The information supplied by Inspectahire was crucial for determining the remaining material thickness and overall condition of the tubes. Despite significant pitting, the condition was within acceptable parameters. Consequently, the tubes were sandblasted and coated with a marine growth retardant to manage the condition until the next planned dry dock in 36 months.
Since the initial inspection, Ethereal has been active on the water more frequently, thanks to the insights gained. Inspectahire has been re-engaged for two out of the last three full dry dock operations, providing updated condition assessments of the tubes globally, including in the USA and Europe. This ongoing partnership has ensured Ethereal remains in optimal condition, reflecting the success of the initial intervention.
