In Part Two of Box losses don’t stack up the discussion centred around possible regulatory failures, including a look at the loading of ships and the bending of rules to allow more cargo to be loaded on board the vessel. The importance of this alleged over-loading will mean that the vessel handles differently and may increase the forces on lashing gear, that was originally designed to safeguard loads on much smaller vessels. Lashing gear designs and specifications have not changed since the early 1980’s.
The only changes to securing the cargo on board modern, larger, vessels is the widespread use of automatic twistlocks. Other than that the lashing bars and securing on lashing bridges remains the same today as the early ships in the container business back in the 1980’s. Given the lack of changes cargo securing on board container vessels, originally for ships of up to 3,000TEU, the forces imposed on this gear on a 15,000-24,000TEU ship could be too much for the lashing bars and bridges.
In the event that the loading of the vessel exceeds the GM rules any container that is over-weight can add to the effects of the movement of the ship and the extra weight may see the vessel suffer greater rolling motions. However, the investigation into the loss of containers on the MSC Zoe in the North Sea revealed that modern ultra-large container ships are wider and more stable. Meaning that when the vessel rolls it wants to return to the upright position, rapidly, it will then pass the upright position and continue rolling, when the momentum of the initial roll is lost the vessel will roll back again in the opposite direction.
According to the Dutch investigation board these motions can have large accelerations and the forces on lashing gear may exceed their maximum design force. It has been acknowledged by industry experts that this could be a difficulty, and class cannot confirm the forces applied beyond an angle of around 15degs.
However, in addition to this a former master, now an expert in container shipping accidents believes that there could be another force at play. The lower four or five tiers of containers are held in place by lashing rods, fixed to lashing bridges on the vessel structure. And the remaining four or five containers above are held by twistlocks.
Increased use of automatic twistlocks has become the norm as vessel owners and operators want cargo handling operations to be as brief as possible, it is quicker to use automatic twistlocks than to have stevedores manually fix the cargo in place.
Automatic twistlocks, one on each corner of the container are activated, that is unlocked, when the weight of the crane spreader pushes down on the box. According to the accident specialist, when a ship rolls in a storm the force on the lashing bars, on the high side of the vessel holds the containers in place, but the motion of the top tiers of cargo is such that it could replicate the downward force of a crane’s spreader. As a result the twistlocks are released and the container stacks collapse.
Independent stowage co-ordinator Neil Wiggins, a former seafarer who said that in the past, when ships were smaller, one or two boxes were lost in rough seas rather than the 100’s we see today, believes that these forces are coming into play and the major changes to the vessel designs over the last 10 years has been the size of the vessels and the use of automated twistlocks.
“Boxes are coming apart [from each other], you look at the pictures and the boxes are all lying higgledy-piggledy on deck,” added Wiggins, pointing out that some of these containers could be filled with dangerous goods, including explosives or flammable liquids.
“Looking at the images of the accidents, often the stacks weren’t collapsed with the boxes locked together,” noted Wiggins. He went on to say,
“In a storm you turn a vessel into the weather to reduce the risk of parametric rolling, but this inevitably leads to the vessel pitching, sometimes heavily, and this can engage significant acceleration forces on the containers which could ‘tell’ automatic twistlocks to unlock, so that when the ship rolls as well, anything not held with lashing bars is at risk,” explained Wiggins.
According to the anonymous captain, Ben Jones (see Parts One and Two), there may also be a difficulty with twistlocks not engaging properly as the cargo is loaded. “We witnessed many auto twist locks being placed at four corners, but it’s wasted if they’re not being seated properly between the containers. The duty officer and crew need to understand the shape and types of twistlocks onboard their ship specific type,” he said.
In addition, Jones believes the industry must pay attention to training, “Regular familiarisation training done by the chief mate is essential for all deck crew prior to cargo operations. Bright colour coded twist locks are essential for better visual checks at higher positions on deck.”
Assuming the twistlocks are seated properly the event of turning the ship into a head wind and sailing at nine-10 knots for an extended period means that the vessel will be delayed, and “The owners will shout because of that delay,” said Wiggins. And if masters misjudge the situation they fear they will not get another commission.
“When the vessel docks the owners’ rep [representative] will come on board and say here’s the course we gave you and here’s the course you took. It’s difficult for masters to ignore that,” claimed Wiggins.
Container News asked a number of carriers to respond to questions around the issue of stack collapses, only Ocean Network Express (ONE) responded, but the Singapore carrier did not answer our questions directly.
“We understand several investigations are still ongoing on the recent cases. From what we understand, no investigation concluded yet. The cases could have been caused by several factors combined and we think it is premature to determine the cause for all the cases.
“While there is no direct discussion among shipping lines on this issue, we, as the industry, take it seriously and an industry organisation such as World Shipping Council will take initiatives on and countermeasures once we have more findings from the investigations,” responded ONE.
Meanwhile, the WSC said, “Given that all reports are not ready, we can only speculate. Indications are however that there is no single cause of the recent incidents, but that the incidents rather were caused by a number of contributing factors. It appears, however, that weather may have been the common contributing factor in all incidents.”
According to captain Jones vessel operators should consider longer berthing periods at port to allow for cargo operations to be completed and to “avoid a hectic schedule for larger vessels”. In addition, he suggested longer rest hours for crew as well as adequate time for checking cargo lashing at sea or in port.
He concludes, “Proper packing, stowage and securing of containers, and reporting of correct weights, are of key importance to the safety of container ships and their crews and cargoes, the shore-based workers and equipment and of the environment.
“Crew members must maintain a sharp eye on cargo operations, to ensure that errors are prevented. While at sea, regular checks and tightening of the lashing gear, including turnbuckles and associated check nuts, will help keep the containers safely stowed.”
Ultimately, reducing the number of stack collapses and cargo loss at sea will come down to enforcing existing regulations, making sure that cargo handling operations are completed in port, even if that means that ships spend more time, raising costs, in port. Moreover, there is a critical need for technical fixes and redesigns of lashing equipment making sure that lashing bars and twistlocks are fit for the purpose, and the loads, for which they are expected to deal with.
Source: Container-News
