DNV GL’s business director tankers Catrine Vestereng has announced a new notation aimed at modern LR2 tankers
Those vessels with easy-to-clean corrugated tank walls, deep-well pumps and high-performance tank washing machines can use the DNV GL class notation ITC to prove to cargo owners that they can clean off crude oil residues effectively and switch quickly between dirty and clean oil products.
The new ITC class notation from DNV GL specifies that tanks must be fully coated and the coating must be compatible with any cargo the ship is intended to carry. The cargo tank piping must either be coated or made from stainless steel. There are additional requirements regarding the materials for the heating coils and the tank-washing and pumping systems. In addition, a dedicated oil residue tank must be provided on board.
According to DNV GL’s vice president and ship type expert Olav Tveit, the ITC notation has three mandatory qualifiers. The first qualifier specifies the coverage of the tank-washing machine: 80% of the total cargo tank surfaces must be covered as a minimum. The coverage implies the tank-washing machines must have a certified throw length. “This means DNV GL does not consider it sufficient for the water jets from the washing system to simply reach the tank walls at that distance. DNV GL also requires a minimum impact force that translates to a certain cleaning effect of the water jet.”
The second qualifier addresses stripping efficiency, which is indicated by the permissible amount of cargo residue left in a cargo tank and the piping after discharging. The draft version of the new rules proposes a maximum of 3 m3 or 3,000 L. Ships achieving a lower amount of residue will be at an advantage.
The third qualifier is the combined total area of upward-facing horizontal structures inside a cargo tank, excluding tank bottom and deck, in square metres. Mr Tveit said “Most conventional crude oil tankers in the 115,000 dwt range are fitted with horizontal structural elements, such as stringers, as well as vertical deck girders, web frames and large brackets. Their horizontal surfaces increase the area where sludge from crude or heavy fuel oil can accumulate, and vertical structures create shadow areas which the tank-cleaning machines cannot reach.”
Mr Tveit said “Using deep-well pumps in each cargo tank instead of a pump room allows shipowners to better strip the cargo tanks and piping from cargo residue and also simplifies the cleaning of the tanks and piping. The reason is that all cargo piping is located on deck. In addition, using deep-well pumps also enables better segregation when different cargoes are carried on board. Lastly, not having a cargo pump room means more volume can be allocated for cargo. If owners are willing to make the necessary investments required for the ITC class notation, their vessels will be in a better position than a traditional ship to switch between cargoes rapidly, depending on the qualifiers they choose.”
DNV GL has been nominated for two Tanker Shipping & Trade Awards. The first is the Technical Innovation Award 2019 for the digital twin project Nerves of Steel and the new generation tanker notation has been nominated for the Tanker Safety Award 2019. Vote on the nominations here.
DNV GL’s ITC notation is an example of class helping to optimise shipping. See and hear more examples at the Optimised Ship Forum on 11 December 2019 in London.