21 Dec 2021

5-year survey for Port Nelson Tug ‘Toia’

Port Nelson is one of Diverse Engineering’s regular clients, bringing a variety of jobs throughout the year. In December 2021, its Damen ASD Tug ‘Toia’ was due for her first five-year survey, requiring checks and maintenance in accordance with marine industry rules and regulations.

The general maintenance aspects of the job included spot repair and painting to set the boat up for the next five years. Her rubber fenders (designed to last for the tug’s lifetime, though the straps must be replaced to mitigate UV damage) were removed by crane to enable proper access for anti-corrosion maintenance to the areas behind them. All cathodic protection anodes had to be inspected and changed as required and all sea grills were cleaned and checked.

As ‘Toia’ is a new vessel the propulsion units remain under warranty of the global manufacturer, Kongsberg Maritime, meaning all work had to be completed under supervision. Propulsion and drive shaft seals had to be inspected and serviced in addition to checks on all drive gearing, which involved taking readings in close consultation with Kongsberg in Australia.

A major aspect of the survey was removing the 4-ton propellers for checking and polishing in Diverse Propellers’ workshops as well as taking out and replacing the seals, which are set up in a particular sequence. If worn, these can cut a groove in the liner allowing water ingress and subsequent leakage; correct procedures must be followed at every step of the process and this was completed on site, with oversight by Kongsberg via mobile phone/video link, allowing them to receive visuals for warranty compliance at each stage.

Refitting the props also required close liaison with Kongsberg to allow monitoring of the sequences, pressure and gauge readings as the propellers are fitted to the drive shafts without keys, relying on a tapered fitting alone. Correct fit is critical, as the bonding process is achieved entirely through pressure. Using Kongsberg’s special hydraulic ram, Diverse Engineering’s mechanical team took the pressure up to the designed level to push the props into their final specified position, to a predetermined measurement. Final calibration checks were then undertaken and verified before end caps were bolted into position to finish the process, prior to protective (Prop-Speed) coating.

Diverse has established a good rapport with its Kongsberg colleagues and both parties are comfortable working together in this new, remote way necessitated by CoVid-19 quarantine restrictions. In the future this system may well become the norm, offering a more cost-effective method for the client, as well as allowing increased time efficiency for engineers.

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