With environmental regulations and fuel economy dominating the shipping press headlines, any mention of efficiency and hull coatings is normally reserved for ecoefficiency technology; improving in-transit operational efficiencies, reducing fuel consumption as well as associated emissions.
However, fully optimising real success in sustainability and efficiency generation is based on looking at every opportunity within the supply chain to improve performance.
For tanker companies, improving efficiencies and simplifying the carriage of liquid cargoes, be it innocuous materials, such as vegetable oils, to more sensitive and potentially harmful substances, such as ethylene dichloride and caustic soda, can make a significant difference in optimising vessel earnings potential.
For example, deepsea parcel tankers spend about one third of each voyage in port loading and unloading cargoes. Being able to switch easily from one cargo to the next with minimal downtime and tank cleaning, is a prerequisite in driving competitive advantage, as well as reducing port time and calling costs.
Coatings for tanks can therefore make a significant difference. However, cleaning standards have become far tougher and more stringent and methanol washing, historically the most effective tank cleaning method, has been largely banned.
The most commonly used type of coating on mild steel tanks is epoxy phenolic, which provides broad cargo carriage capability but can absorb and retain certain cargoes. This can create a difficult cleaning challenge to remove any absorbed cargo and thus minimise the risk of contaminating subsequent cargoes. A recovery period may also be required. All of this can incur expense for a ship operator in terms of time and money.
The next most common type are zinc silicate coatings, which provide resistance to solvents and pure chemicals but are limited in their use due to an inability to resist acids and alkalis. The rough surface of zinc silicate coatings can also be difficult to clean, again costing time and money.
In addition, costs of on board cleaning are significant. For example, bunkers for hot water could mean a tank cleaning operation alone could add over $100,000 to operating expenses for one full vessel clean - and this doesn’t take into account manpower, costs of cleaning materials or downtime which can easily be in excess of 10 days.
To meet this challenge and after much investment in research and development, International Paint launched the patented Interline 9001 in 2011, a new bimodal epoxy coating for chemical tankers’ cargo tanks.
Interline 9001 is a chemically resistant tank coating based on a special combination of low and high molecular weight polymers creating a loosely bound, but highly cross-linked flexible network chain on ambient curing. The post cure process then locks these network chains firmly together to provide a highly chemical resistant paint film offering low absorption properties and easy clean while still maintaining flexibility to ensure crack resistance on welds when subjected to vessel flexing.
The new coating has been independently proven to reduce cleaning times by up to 70%, delivering greater efficiency and flexibility in the operation of chemical tankers, making a big impact on the bottom line for owners and charterers. It also has extended chemical resistance, allowing companies to carry aggressive materials and remove recovery periods in addition to maintaining the cleaning benefit of the system.
It can carry all of the cargoes standard epoxy phenolic technology can, plus a further 25% of the large volume cargoes that it cannot. Moreover, it has over 60% fewer cycling restrictions.
Aggressive cargoes
The technology also opens up new - previously restricted - cargo sequences for the carriage of aggressive cargoes; for example, methanol to ethylene dichloride to fatty acids back to back, with no coating recovery required. Its low cargo absorption profile reduces the risk of contamination between cargoes compared to standard epoxy phenolics, or zinc silicates. And with reduced cleaning requirements, comes a corresponding reduction in fuel and CO2 emissions. In addition, a low volatile organic content (VOC) and 80% volume solids helps to enhance the customer’s environmental profile and sustainability.
However, as with any efficiency generating technology claims are one thing; it is providing the in-service substance and validated proof that really counts. In September 2011, MH Simonsen, a Danish, family-owned tanker company, operating predominantly in the North European small tanker market, became the first company to apply Interline 9001 to all the tanks of its 1,639 gt, 2,174 cu m cargo capacity chemical tanker - Oradana.
Oradana transports a full range of liquids, including the extremely aggressive product calcium lignosulphonate. Carried at 80 deg C, this cargo has long been a cause of failure for traditional coatings like phenolic epoxies and zinc silicates, rapidly leading to steel degradation.
Meeting this challenge, together with the need for easy cleaning and transition between difficult to clean cargoes such as lecithin and fatty acids was critical for Simonsen and a key deliverable for Interline 9001.
Commenting on the success of Interline 9001, Allan Skovlund Nielsen, MH Simonsen’s technical manager, said: “Our trademark is top quality tanks for refiners and Interline 9001 has not let us down. As a result of using this product, we are able to trade aggressive chemicals and the time to clean to cargo surveyors’ satisfaction has been significantly reduced versus traditional coatings. Calcium lignosulphonate is a key cargo for us and we cannot carry this in phenolic, or zinc tanks. Lecithin and fatty acids historically caused us many cleaning headaches but this process is made much simpler with the use of Interline 9001.”
In the many months of service, Interline 9001 has also enabled the smooth transition between other high temperature and difficult to clean cargoes on the Oradana. This includes fish oils, molasses, vinasses, crude rapeseed oil, urea ammonium nitrate, palm olein and fertilisers.
Due to its bimodal epoxy technology, the coating offers extended chemical resistance over phenolic epoxy coatings, while significantly reducing cleaning time and costs through low absorption of chemicals and a glossy, smooth surface.
*This article was written by Andy Hopkinson, business development manager, International Paint.