The Naval Archiect: July/Aug 2017
Bigger boxships deman a firefighting infrastcture with enhanced capacity explains Matthew Temblay, ABS vice president for containerships.
As recent incidents have demonstrated, the risks from a containership fire increase as the number of containers onboard rises. As container stacks have increased in height and number, the opportunity for a fire to grow in size and scale has grown with them.
We know from our discussions with containership operators that this is a critical risk to their operations which they wanted to address.
Key for the owners and operators is the ability to protect life and cargo onboard. ABS is constantly looking at new approaches to expand safety in the industries that we serve and consistent with the ABS mission to protect life, property and the marine environment, we decided to move forward with the development of a new standard for fire safety.
The result was an update to our guidance for existing containership tonnage, the ABS Guide for Fire-Fighting Systems for On-Deck Cargo Areas of Container Carriers (FOC Guide). By applying the guide, containership owners can apply the same degree of assessment and review to their active fleets that they do for new construction and demonstrate a commitment to safety and fire protection that supports more secure operations.
The primary technical challenge of firefighting is not necessarily structural, but mechanical. As stack heights grow, the systems that supply the fire water to the container decks must have the ability to move a greater volume of water at higher pressures over longer distances. Therefore, building a robust water distribution system with suitable redundancy and capacity is the primary challenge.
The new code goes above and beyond the IMO requirements (SOLAS 365 (93)) in several ways. In particular, the FOC notation requires at least twice the amount of water capacity be available to the container deck.
It also requires that the piping be arranged in a redundant ‘loop’ type design with isolation valves that would allow the system to isolate damage and operate after a single break in the piping system.
FOC also requires approximately twice the number of fire water monitors (nozzles) than is required by IMO, dependent on vessel size. The FOC+ notation adds a requirement for the protection of the hatch covers that is not addressed by the IMO regulations.
FOC-R is a modified version of the FOC rules that were developed as a means of applying the lessons learned creating FOC to existing vessels. While FOC is intended to be applied to new construction, FOC-R applies the aspects of FOC that can be reasonably installed and retrofitted on an existing ship during a normal drydocking.
In researching the topic to create the new guidance, our main task was to evaluate the water supply capacity that would be required to shield the radiant heat from a container fire from igniting a new fire in an adjacent bay.
This was primarily accomplished through the use of 3D fire modelling software that can predict the transfer of heat from one location to another. Multiple fire scenarios were modelled to determine the minimum water capacity that would be needed to create a reasonable water spray barrier between container bays.
A containership fire is very difficult to extinguish. In most cases, a ship crew’s best hope is to contain the fire and let it burn out. The physical activity required onboard to operate these firefighting systems is both dangerous and strenuous.
In considering the most important factors naval architects should be aware of from a design perspective when seeking to manage fire risk onboard container ships, the arrangement of the access ways and equipment should be optimized for the safe and efficient use of the crew.
Whether or not we have seen the pinnacle in terms of ever-bigger containerships has implications for fire safety and also other technical factors. As naval architects, we are technically capable of designing even larger vessels than the biggest ships being built today.
The biggest factor currently affecting the continued growth of container ships is the shore-based infrastructure required to support them. There are a limited number of ports that can currently handle a 20,000 TEU-plus ship. While slot costs may continue to decrease as vessels get larger, the overall functionality and flexibility of the vessel decreases as it can operate in fewer and fewer ports. Ultimately this is a commercial decision that the liner operators will make as trade conditions evolve and new technologies are incorporated into ship designs.
However, the most significant trends we observe in terms of containership design are around safety of the cargo. Container deck firefighting is one of the biggest areas of concern for ship owners today. We have received significant feedback on the publication of our FOC and FOC-R notations from owners looking to implement the rules.
Container lashing analysis is also an important topic. As container stacks get taller, the effects of their movement at sea grow in significance. Traditional analysis methodologies for designing lashing systems are no longer able to accurately predict the dynamic loads applied to lashing equipment in taller stacks.
This led ABS to publish its new Guide for Certification of Container Securing Systems (The Lashing Guide) and new companion software, ABS C-LASH. Central to the Lashing Guide is a newly developed non-linear lashing analysis procedure that represents a significant improvement over traditional formulas for container securing.
Coupled with new easy-to-use software that simplifies analysis of container lashing arrangements, the resources enable a more accurate representation of the loads in taller stacks, allowing operators and designers to develop safer, more efficient lashing system arrangements on board.