Modern chemical tankers of IMO Ship type I, II and III are designed and equipped to handle a very wide range of liquid cargoes ranging from relatively innocuous materials such as vegetable oils to more aggressive types such as ethylene dichloride and caustic soda. Most vessels will have coated mild steel tanks, stainless steel tanks or a combination of both.
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 minimize the risk of contaminating subsequent cargoes, according to the company. 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 is zinc silicate, the company said. These coatings 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. Bunkers for hot water for example could mean a tank cleaning operation alone adding over $100,000 to operating expenses for one full vessel clean and this doesn’t take into account manpower or costs of cleaning materials.
Interline 9001 is designed to deliver greater efficiency and flexibility in the operation of chemical tankers, easily switching from one cargo to the next with minimal downtime. It can carry all of the cargoes standard epoxy phenolic technology can, plus a further 25 percent of the large volume cargoes that it cannot and has over 60 percent fewer cycling restrictions, according to International Paint.
The technology opens up new (previously restricted) cargo sequences for the carriage of aggressive cargoes, for example, methanol to fatty acids to ethylene dichloride back to back, with no coating recovery required.
Its low cargo absorption profile reduces the risk of contamination between cargoes and combined with its smooth, glossy surface, can cut cleaning time and materials by up to 70 percent compared to standard epoxy phenolics or zinc silicates.
With reduced cleaning requirements, comes a corresponding reduction in fuel and CO2 emissions. In addition, a low volatile organic content (VOC) and 80 percent volume solids helps to enhance operator environmental profile.
Based on bimodal rpoxy technology, Interline 9001 is a blend of polymers. Firstly, a special combination of low and high molecular weight polymers creates a loosely bound, but highly crosslinked 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 whilst still maintaining flexibility to ensure crack resistance on welds when subjected to vessel flexing.