An increasing number of requests from operators who are considering the use of Y-splitters in order to increase the reefer capacity on their containerships beyond their designed limit.
However, it says that when doing so, there is a risk of overloading the power cables, as this would generate excess heat and increase the potential of fire. This risk is further enhanced by the absence of frequent monitoring and review, of the condition of the extra cabling, sockets, plugs and reefers by the crew.
For this reason, Standard provides key considerations for operators to have in mind when conducting their own risk assessment for carriage of additional reefers beyond the ship’s designated capacity.
- Comparison of electrical load exerted by the additional reefers against capacity of power source
There is a reason why ships are assigned to carry a specific maximum number of reefers. This takes into account the generator capacity against the loads exerted by cargo (reefers), machinery and domestic supply, and an additional safety margin.
While the latest reefer designs are known to be far more efficient and consume less energy than previous models, many container fleets still have a big share of older reefer versions in use today. Such old reefers tend to draw a much higher current than the newer designs. There is also a need to consider reduced efficiency of the generators due to ship’s age
Moreover, the power consumption of a reefer container depends on several factors including weather and storage conditions, container type, and may vary significantly depending on the type of commodity, i.e., chilled or frozen goods.
Generally, the higher the internal temperature, the higher the electrical power consumption. Once the cargo has been cooled, the average power consumption falls. In cases where there are several hot reefer containers, when these are turned on at the same time, there is a possibility that the current drawn may exceed the capacity of the power source.
- Safety aspects related to the use of Y-splitters
Y-splitters allow multiple reefer cords to connect to a single power source receptacle; however, there is a risk of power outtage/tripping, blackout, fire and other consequential liabilities if the loads exceed the capacity of the generators.
There is also a need to consider the rated capacity of the Y-splitters, reefer extension cords, sockets and plug points – these should not be exceeded at any time.
Y-splitters when improperly handled can bypass the integrated safety designs of the receptacle panel – one should not connect or disconnect reefer plugs to a splitter while it is energized. It is recommended that the reefer plugs are connected to the splitter first and then the power source can be connected and energized
The splitter and associated equipment should be in a sound condition and able to withstand shock load and power surge. Multiple Y-splitters on the same circuit should not be used and if required, the ship’s generator capacity shall be increased safely by using power packs.
One way of distributing the electrical load is by plugging a chilled and frozen commodity reefer on the same splitter. However, knowing that the planning is generally done on the basis of load and discharge ports, it might not always be possible to plan the reefers or distribute the loads effectively.
Alternatively, some operators prefer to use ‘splitter box’ as it safely regulates the power to the reefers (and prevents both reefers from switching on at the same time).
- Stowage location of additional reefers
Provided that all the factors have been considered and it has been agreed to carry additional reefers, their stowage location onboard would be an important factor to consider – the additional reefers should be carried above deck.
If these are carried inside holds, the cargo hold ventilator fans may not be able to keep up with the required air exchange, leading to overheating and subsequent issues with the cargo.
If the reefer containers are stacked higher in the tier, there will be a risk of personnel injury (crew or stevedores) when plugging/unplugging the reefer at higher tier on deck or trying to monitor the container temperature during the voyage.
If there is a malfunction of a reefer carried at a higher tier on deck, then there will be nothing much the crew can do to rectify the issue which may lead to a cargo claim. Alternatively, the vessel will need to be provided with portable platforms for this purpose.
In conclusion, when considering to carry additional reefers beyond the ship’s designated capacity, it is vital that a proper calculation is done to ascertain that the loads exerted by the reefers do not exceed the capacity of the ship’s power source and keeping in mind the reserve power that will be required by the ship’s machinery and domestic consumption. The power calculations should be verified and approved by the Classification Society.