Scrubbers, lengthening existing box ships and stowage are all under the spotlight for class societies
DNV GL published a new class notation, Emission Reduction, for exhaust gas cleaning systems in July this year, as it revealed that one of the biggest markets for scrubbers is the box ship sector.
DNV GL head of section for environmental certification Stine Mundal told this publication “Scrubber activity was quite low in 2017 but we really see interest picking up in 2018.” This is due to the upcoming 2020 low sulphur cap.
DNV GL gathers monthly global statistics for ships confirming scrubber orders – and interestingly the container ship segment has now overtaken the cruise sector for the most confirmed orders and installed scrubbers. As of July, there are 178 confirmed scrubber projects for container ships – only beaten by 185 orders for bulk ships. This places it second in all ship segments for scrubber installations.
Explaining the boom in orders for container ships, Ms Mundal said “These ship types spend so little time in the ECAs which were introduced in 2015, there was no business case – but now with the upcoming sulphur cap, this is a completely different story and that is why these ship types are seeing the economic benefits of using scrubbers.”
Concerns over the low sulphur fuels available are also fuelling the scrubber surge. Ms Mundal said “Some operators are worried about the availability of low-sulphur fuel.”
Furthermore, new compliant blended fuels will be coming onto the market – but as they don’t exist yet, engine makers have not been able to test their compatibility with their engines. “There is a bit of uncertainty about low sulphur fuels that will be available, how available they will be and how they will behave with machinery,” said Ms Mundal.
‘Jumbo-ising’ gains momentum
Meanwhile DNV GL ship type expert for container vessels Marcus Ihms singled out two projects the class society is classing that are “challenging and interesting”: MSC’s new 22,000-TEU vessels currently being built and the lengthening of existing CMA CGM and MSC box ships.
CMA CGM and MSC are lengthening eight and 10 14,000-TEU ships respectively to turn them into 17,000-TEU box ships. This trend has been referred to as jumbo-ising.
Mr Ihms told this publication “From an engineering point of view it is challenging and to my knowledge a lengthening of this size of vessel has never been carried out before.”
The work is being carried out in China, with the first vessel – one belonging to CMA CGM – expected to be completed at the end of August this year.
Mr Ihms commented “The main issue is the longitudinal strength of the vessel. The vessels are relatively young – the youngest is less than five years so you can imagine that in their original layout they are not designed to withstand a lengthening.”
He said the extra strength that needed to be provided was “quite substantial” – the 10% length increase in the vessels equates to 20% more strength. “That has been a challenge as the shipowners and yards do not want to reinforce every part of the vessel but have a smart solution including a short production period.”
He said the solution was to add a large structure by way of the main deck to provide additional longitudinal strength, meaning the yard “did not have to reinforce existing parts but instead added something extra to the vessel”.
Mr Ihms said deck container capacity was enhanced in addition by increasing deckhouse and the funnel height.
He feels lengthening vessels will become a stronger trend within the box ship sector. “It is a relatively small investment compared to ordering a newbuild of 17,000 TEU. It is cheaper and faster to upgrade current vessels and makes 14,000-TEU ships much more competitive,” commented Mr Ihms. “14,000-TEU vessels are the work horses and overnight they become much more competitive.”
Boosting stack safety
Elsewhere, Lloyd’s Register (LR) has been working closely with ultra large container ships (ULCS). It has classified numerous ULCSs with TEU now in the 20,000 range. Lloyd’s Register lead specialist structural analysis, marine and offshore, Seb Brindley said “With over 50% of their cargo on deck, the importance of on-deck stack security and safety is vital for commercial success.”
LR has developed a methodology to help operators maximise their vessels’ potential. Mr Brindley examined the benefits. “This unique methodology is specifically engineered and validated to capture the stack behaviour, allowing clients to quickly, easily and reliably ascertain the stack safety… the importance of the lashing bridge strength, container corner post rigidity and twistlock separation can be investigated.”
Mr Brindley singled out the closed end of a typical 40 ft inner stack with single external lashing as an example.
Homing in on twistlock separation, he said this is inherent in the twistlock design due to a slight gap or play in its connection with the corner casting allowing it to be easily fitted and removed. The gap between two container corners connected with a twistlock can increase about 18 mm under tension. “For external lashing arrangements, this phenomenon not only causes a substantial increase in the lashing rods’ load but also reduces the compressive load in the corner posts,” Mr Brindley commented.
He said for the examined stack, there are four main states due to the interaction between twistlock separation, lashing rod loads and lashing bridge stiffness.
- In state one there is minimal support from the lashing bridge, resulting in excessive stack deformation. Multiple twistlocks are in tension causing a large load in the port lashing rod. This force pulls the stack to port relative to the lashing bridge and in some cases may cause the starboard lashing rod to be in tension, further increasing the load in the corner post.
- In the second state, with increased support from the lashing bridge, only the port lashing rod and the twistlock below the lashing rod are in tension. An increase in the lashing bridge stiffness only changes the separation of this twistlock and the lashing rod tensile load and the corner post compressive load remains unchanged.
- In state three only the twistlock below the lashing rod is in tension and an increase in the lashing bridge stiffness transfers the load from the twistlock to the lashing rod, reducing the corner post load.
- In state four, the twistlock below the lashing rod is in the float condition. Similar to state 2, the loads in the lashing rod and corner post are independent to the lashing bridge stiffness.
Mr Brindley summed up “Twistlock separation, lashing bridge deformation and corner post compression influence the stack behaviour.”
Stine Mundal (DNV GL)
Stine Mundal is head of section for environmental certification in DNV GL - Maritime and has been with the company since 2009. She is responsible for the global service delivery of approval and certification of diesel engines, exhaust gas cleaning systems and ships according to Marpol Annex VI, Emissions to air. Ms Mundal previously held several different international positions within DNV GL within different fields of ship classification. She holds a Master of Science degree in naval architecture and marine engineering from the Norwegian University of Science and Technology.
ClassNK: digitalisation is a “game-changer”
One of the main trends in the container industry today is digitalisation. All class societies are heavily involved in this, including ClassNK.
ClassNK senior corporate officer, director of innovation development division Hirofumi Takano said “We help the maritime industry maximise profitability and explore new business models by offering digital solutions and giving guidance on cyber security.” He singled out ClassNK’s Ship Data Center (ShipDC), as an example of a data platform that offers companies the ability to safely store and manage their data and make it available to authorised stakeholders.
He said “As times change, the means for collecting and analysing data have changed and potential benefits have increased. That’s why ClassNK established the ShipDC subsidiary in 2015.
“Soon after, I observed a change in the mind-set of maritime leaders, especially among shipowners and ship operators, about the value which data collected from ships can provide to their organisations.” He said ships are now more often equipped with sensors which measure and transmit data and parameters from machinery and the vessel in real-time. “This data can be made valuable by applying intelligent analytics and drawing conclusions in order to optimise voyages and the efficiency of ships.”
He observed “Without a common platform like ShipDC, multiple interfaces and exchanges could be necessary to achieve the same results, while having to make comparably higher investments and being exposed to a potentially higher cyber security risk.”
He summed up. “I believe the next five years will completely change the way we work and that digitalisation will be the game changer.”