Water quality concerns support BWTBoat concept
Indian classification society IRClass has proposed a new role for its BWTBoat concept, which is primarily designed to deliver treated ballast to ships. The alternative role involves operating as a powerful filter in ports with challenging water conditions, to provide clean water to ships that can then use their onboard ballast water management system (BWMS) to treat the water.
In a report prepared for Marine Propulsion’s sister publication Ballast Water Treatment Technology, BWTBoat’s inventor and project manager Sandip Patil referred to what he called an “eye-opening” submission by South Korea to IMO’s Marine Environment Protection Committee in July 2017. That paper reported that BWMSs do not work properly in ports with challenging water quality, either because they get clogged, or becuase ballasting operations are delayed due to frequent back flushing.
The South Korean paper, similar to another from Canada, mentioned the possibility of receiving clear ballast from port-based facilities, if available. BWTBoats could do that, Mr Patil said, because they have a much larger water catchment area than a ship and multiple filters to deliver flows of up to 10,000 m3/h, he explained.
In his paper, Mr Patil said that although BWMSs are mostly tested at real-world biological loads, they are not subjected to real-world sediment loads. “G8 [testing] guidelines only specify the total suspended solids (TSS) condition as >50 ppm (>24 ppm for USCG). [But] in the real world, TSS load can vary up to 1,000 ppm, directly affecting – by delaying or stopping – cargo operations,” he said.
• IRClass has been working on its concept since 2013 and Mr Patil’s report also described a design development that has halved the concept's cost and means that ships would not need any retrofitting or deck connections to receive treated ballast water from BWTBoats. He described the new arrangement as acting “like [an] external plug-in to [a] ship’s sea chest”.
Ballast-free design avoids need for BWMS
Partners in a project to develop a ballast-free LNG carrier began the second phase of their initiative in March. GTT, Lloyd’s Register (LR), Dalian Shipbuilding Industry Corporation (DSIC) and Exmar are working on a design for a 30,000 m³ LNG carrier concept, which they have dubbed the ‘B-Free’ design.
It received approval in principle from LR in December 2017 and Phase 2 aims to develop the design further and validate results from the first phase by applying more detailed analysis and verification, including model testing.
For unladen mid-size LNG carriers, ballast water is more critical to achieving sufficient draught for propeller immersion than for stability. The B-Free design intends to do this by having a triangular-shaped lower part of the hull, LR explained in a statement. This allows the vessel to sit deeper in the water when unladen, achieving the necessary propeller immersion for its 5.6 m diameter propeller while maintaining stability.
The design also potentially offers lower construction and operational costs because there is no need for a ballast water management system.
The project partners said that, compared to a conventional 30,000 m3 LNG carrier, they have been able to provide the same cargo-carrying capacity with their B-Free design in a much smaller hull. It uses GTT’s Mark III membrane in a two-cargo-tank configuration, rather than the three- or four-tank arrangement usually used.
The B-Free LNG carrier has a lightship weight of about 1,000 tonnes less than that of the conventional ship, resulting in improved harbour access and lower harbour fees, they said.
During Phase 2 of the B-Free LNG carrier design project, DSIC will concentrate on ship layout and performance, including: hull line optimisation, utilising computational fluid dynamics; ship model test verification; propulsion selection; and hull structure basic design.
ClassNK ballast rules match BWMC
Japanese classification society ClassNK has released a new set of technical rules and guidance for shipowners covering ballast water management system (BWMS) installations. They “draw upon the knowledge of ClassNK’s in-house experts, incorporate guidance from the International Association of Classification Societies and satisfy Japanese domestic law,” the organisation told Marine Propulsion in April.
ClassNK's Rules and Guidance for Ballast Water Management Installations were issued on 8 September 2017 to coincide with entry into force of IMO’s Ballast Water Management Convention (BWMC).
In addition to meeting the BWMC requirements, its rules “stand as a regulation requirement”, it said in a statement at the time. At the same time, the society made corresponding amendments to its Regulations for the Classification and Registry of Ships.
ClassNK also advised Marine Propulsion that its 3D laser scanning technology, called Peerless, “offers shipowners the opportunity to assess how to retrofit BWMS on their ships quickly”. This helps avoid time-consuming manual work by taking point data from 3D scanners and converting it into 3D models. This can be done within one or two days, rather than the 10-14 days required for manual processing the class society said.