Loading software is being continually updated to reflect best practice. New developments include revised route-specific lashing rules and parameters that factor larger vessels
Onboard loading computers are applying increasingly stringent and specific lashing rules which are specific to the route a vessel is sailing. This is having a marked improvement on safety and enabling greater flexibility in creating cargo loading plans.
“Route-specific and weather-specific lashing rules [enable] increased cargo intake and more flexibility in container stowage,” says Navis product manager for MACS3 Gerald Lange.
He notes a trend for new container lashing geometries as particularly useful, explaining they are applied in cargo securing systems and calculated on loading computers: “The algorithms used to calculate lashing forces are becoming more complex; in the past, simpler formulas were built into loading computers.”
According to Mr Lange, the industry as a whole will benefit from this development, as it increases the accuracy when calculating lashing forces, meaning a better approximation of the real physical relationships causing the forces acting on the containers.
“The update allows the maximum theoretical capacity for the vessel to increase by approximately 5%”
“Having an approved-by-classification-society lashing calculator on board – while we cannot say it will 100% lead to no containers falling out – it [provides] an increased safety margin to avoid incidents.”
“There has been a lot of progress in the rules [over the] last few years; Route Specific Container Stowage+ (RSCS+) is one of changes that we have worked on.”
It was at SMM September 2018 that Navis launched DNV GL’s latest lashing regulation option, RSCS+, on its loading computer MACS3. This has now been launched on a Claus-Peter Offen container vessel.
In Q4 2018, Navis’ ship-specific MACS3 Sealash module was introduced on board the 8,000 TEU container vessel having been approved by DNV GL. The vessel - owned and managed by Hamburg-based Offen group - is now able to apply the latest update of RSCS+ lashing regulations from DNV GL (the July 2018 edition). The update allows the maximum theoretical capacity for the vessel to increase by approximately 5%.
As part of the upgrade within RSCS+, the vessels can now access worldwide routes through DNV GL’s Veracity, without additional approval from class.
Using the class-approved lashing computer, the cargo officer can choose between calculations for long-haul routes and short sea voyages as part of RSCS+. As a result, more cargo can be safely loaded on the vessels, based on typical trade patterns and weather forecasts for short sea voyages.
Mr Lange says: “In short-voyage mode a reduction factor given by the rule can be applied if a weather forecast with a maximum wave height is available.” This provides the lashing calculation with more details, resulting in more flexibility in stowage of containers and allowing heavier cargo to be placed higher in the stack.
A vessel can switch between RSCS+ long-haul and short-haul calculations on a single route; for example, using the long-haul module for a trip from Asia to Europe, but once in Europe, moving to short haul as the vessel moves between European ports.
For Navis, a major part of the project involved the integration between its MACS3 onboard loading computer and its XVELA planning and collaboration platform, used for carriers and ports to find the best port loading and unloading plan.
XVELA vice president global sales Martin Bardi says: “The integration between MACS3 and XVELA allows the terminal to validate stowage plans by using the same criteria as the ship’s crew.” Allowing the plans to be viewed by both crew and the terminal operators “reduces the number of iterations it traditionally takes to get plans approved by the ship captain. This ultimately increases vessel productivity at the port.”
While both the MACS3 and XVELA software share the same stability and lashing engine, Mr Bardi notes: “You can plan the ship on one product and then upload the plans into the loading computer, but the loading computer might say you cannot load the ship that way. With our integrated products however, the same criteria that are used on stowage planning for the port can be applied on the loading computer; this dramatically reduces re-iterations.”
Mr Bardi says more than 50% of container vessels are now using MACS3 on board, and major liners like CMA CGM are working with Stowman, the Navis software for stowage planning.
Software for bigger ships
Elsewhere, DNV GL has made changes to its Stowlash container stowage software, to take into account the fact that, as box ships get bigger, the amount of container stacks increases
DNV GL director of business development in Hamburg and executive vice president Jan-Olaf Probst explains: “Container vessels are getting bigger and so operators want to store containers up to 11 or 12 tiers. Therefore, container stacks [exhibit] a totally different behaviour [to when stacks were lower]. Until recently, the first two or three containers on the top of 11 stacks been mostly empty, depending on the loading of the vessel. But vessels do not want to carry empty containers, they want cargo. To achieve this, we need more accurate calculations.”
Jan-Olaf Probst (DNV GL): Non-linear and three-dimensional behaviour of container stacks now considered in stowage software
As vessels have increased in size, so cargo-securing techniques have evolved to cope with the added scale. DNV GL pointed out in its latest Container Ship Update that over the past five years, external lashing has become a “quasi-standard”, especially on larger vessels, because it allows operators to transport greater weights.
“Vessels do not want to carry empty containers, they want cargo”
To address such changes, DNV GL launched its “Modern Deck Container Stowage” (MDCS) solution, which led to the development of a new StowLash software, which uses the ‘finite elements’ method to calculate the forces acting upon the containers and lashing equipment.
Mr Probst says this is the first time the non-linear and three-dimensional behaviour of container stack has been considered in stowage software.
DNV GL tested the results at the Pella Sietas shipyard in Hamburg, where six 40-foot-high cube containers were stacked on top of each other. Steel cables were attached to put a tensile load on the stack, then released in a controlled condition to simulate the rolling of a stack. Instruments arranged around the container stack measured the forces and deflections acting on it.
DNV GL said that the updated software is suitable for calculating both internal and external lashing systems. Innovations in lashing equipment can also be calculated appropriately. For example, the new software allows users to define the type of twist-lock being used, and the new computation model accounts for the fact that lashing rods transfer only tension and not compression forces.
Mr Probst explained the updated software will provide shipowners with “higher flexibility of load distribution in the container stack”.
The new Stowlash 3D software and related rules will take effect in March 2019.