The inspection of ship tanks and holds can be a costly and time consuming affair. As these structures are subject to harsh operating conditions, the coating condition, corrosion, damages and possible fatigue failures must be assessed on a regular basis so that timely repairs and remedial measures can be carried out to avoid catastrophic failures while the vessel is out at sea. For ships such as large oil tankers and bulk carriers, these inspections have to be carried out in their cavernous tanks or cargo holds. The height of such structures poses a challenge to the inspection process and exposes surveyors to potentially dangerous situations.
Ask any Classification Society surveyor about the hull structural surveys for large oil tankers or bulk carriers and you will most likely hear stories about climbing up slippery stiffeners, scaffolding that goes on forever, rafting on oily water inside a dark tank or holding on for dear life at the upper end cradle of a rickety cherry picker.
Using drones to visually check the conditions of remote structural components has the potential to significantly reduce survey time and staging costs, while reducing the surveyors' exposure to dangerous situations.
On 30th May 2017, the Maritime and Port Authority of Singapore (MPA), in collaboration with DNV GL and Pacific International Lines, carried out a trial drone survey on board the Singapore-registered container vessel "KOTA HARUM".
Assembling the drone in Ship Office
Drone taking off from bottom of the cargo hold
The trial took place while the vessel was in Singapore's anchorage. It was conducted in an empty cargo hold with the hatch-covers closed to simulate a tank's conditions. DNV GL used the commercially-available DJI Phantom 4 drone for the trial. The propeller guards were customised to allow plastic rods to be attached. This formed a "bird cage", which acted as a vertical shield. Lights were installed at both sides of the drone to illuminate the dark conditions. The drone was operated by a two-man team: one operator to pilot the drone, and one surveyor to observe the recordings and give directions. With the propeller guards in place, the team could fly the drone extremely close to the ship's structure without fear of damage. The 4k camera also allowed for high-resolution video footages to be taken.
It was a fruitful trial showcasing the drone's ability to provide visual close-up of critical structures at difficult-to-reach locations. The surveyors had the luxury of examining these structures via the hand-held tablet while standing at the bottom of the cargo hold in relative safety. This would translate to potentially significant savings in time and costs, since conventional access methods such as rafting and staging could be avoided.
Visual transmitted by drone to tablet held by Surveyor
Drone making a sweep across the internal structures in the cargo hold
The development of more advanced and better-customised drones by manufacturers promises improved controls, more powerful cameras, thermal imaging capabilities, tank structure mapping, as well as the possible capability of carrying out steel thickness gauging. The advent of technology in the maritime industry is a welcoming tide that brings a whole suite of benefits that were once undreamed of.
MPA welcomes collaboration with like-minded partners in riding this tide and embracing new technologies to bring the maritime world into the digital age. This and subsequent trials on different ship types will form the basis for Singapore to develop the requirements and guidelines for the approval and acceptance of using drones as an alternative survey method on Singapore ships.