IMDG Code requires certain substances to be transported under temperature control due to the properties of these substances to undergo a self-accelerating decomposition, possibly of explosive violence, when the temperature exceeds a certain value.
Self-accelerating decomposition temperature (SADT) means the lowest temperature at which a self-accelerating decomposition may occur for a substance in the packaging as used in transport.
When a Self-reactive substance or an Organic Peroxide require temperature control during transport the compulsory requirement of usage of reefer container is indicated by words “Shall be transported under temperature control” in column 16 of DGL and Stowage Code SW3 in Column 16a of DGL in 36th and 37th amendment of IMDG Code respectively.
The Control Temperature and Emergency Temperature is determined basis the SADT in which the size of package plays a crucial role. For single packagings and IBCs if SADT is 20°C or less the Control Temperature and Emergency Temperature is 20°C and 10°C below SADT respectively.
Actual transport temperature can be lower than Control Temperature however it shall not be so low to form dangerous separation of phases.
Prior stuffing the reefer must be thoroughly inspected, tested and Master must be provided with operating instructions and spare parts. If the Control Temperature is less than +25°C, the reefer must be fitted with audio visual alarm independent from the power supply of the reefer.
Redundant Reefers: Certain Self-reactive substances and Organic Peroxides require dual mechanism reefer which has two independent refrigerating units with separate power supplies and able to start automatically when the running unit fails.
While packing the reefer with packages requiring temperature control and packages not requiring temperature control the packages which require temperature control must be stowed closer to the door for access in an emergency. Similarly if there are different packages with differing control and emergency temperatures the packages having lowest Emergency Temperature should be packed near the door.
Ship staff will monitor the temperature at regular intervals and if due to malfunction if the temperature rise above Control Temperature they will initiate control measures such as repairing the equipment or providing additional coolants when available. If this fails and the temperature reaches the Emergency Temperature ship staff will initiate Emergency Response Measures which may be jettisoning the cargo or rigging fire hoses and pumping copious quantity of water on to the packages inside the reefer to prevent fire or explosion when the temperature reaches SADT.
Quality Control Reefer Shipments: Some dangerous goods which do not require temperature control for safety reasons may be offered by shippers’ in reefers for commercial reasons. These goods may be flammable liquids, flammable gases, flammable solids or corrosive substances. Example: Perfumes, Safety Matches, Paint, Lithium Batteries, Phosphoric Acid, Acetic Acid etc…
When flammable liquids or gases with flashpoint less than 23°C c.c. are loaded in reefers the substance shall be precooled and transported at a temperature at least 10 Deg C below its flashpoint or a reefer with explosion proof electrical fittings is required.
During transport if the reefer fails the Master must disconnect the reefer from power supply and must not reconnect again if the temperature has risen to less than 10°C below the flashpoint. The reefer can continue its journey and discharged at destination as non-operating reefer.
Carriers’ policy: Carriers may have their own policy with respect to set temperature and humidity for dangerous goods in reefers which do not require temperature control for safety reasons as per IMDG Code. One of these is the infamous Calcium Hypochlorite. Some lines insist that they will carry calcium hypochlorite in reefers with +10 or +20 Deg C only. This is to prevent the exposure of cargo to higher temperature which may result in a thermal runaway explosion.
Carrying Calcium Hypochlorite in reefer is a good proactive step to ensure safety. However, since the reefer is a thermally insulated box the probability of equipment failure and resulting trapped heat generated by cargo inside the reefer must be borne in mind while loading on board ships. If the reefer fails the vessel should discharge the reefer at the next port or during long passages open the doors and provide ventilation. It all depends on the Masters’ decision considering the ambient temperature and distance to go to the next port.
Repositioning Empty Reefers: Reefer is a good business for carriers same time repositioning them is a bad business too. In reefer trade lanes carriers may offer non-operating reefers for general goods and dangerous goods so as to earn freight while repositioning. Most carriers do not accept flammable gases in non-operating reefers to avoid the possibility of someone switching on the reefer en route which may result in explosion if there is gas leakage. Some carriers do accept flammable gases in non-operating reefers provided the power cables are secured and blanked.
Primary function of reefer is to carry food grade products. The reefer operator takes care of the equipment avoiding possibility of contamination by not releasing the reefers for carrying goods which must be separated from foodstuff or for tainting commodity.
For goods which require temperature control during transport for safety reason, the Control and Emergency Temperatures shall be indicated on the dangerous goods declaration, as follows:
“Control Temperature: … °C Emergency temperature: … °C”.
Below sections of IMDG Code identifies the actual Control and Emergency Temperatures for certain substances:
– 188.8.131.52.2.3 List of currently assigned Self-reactive substances in packagings
– 184.108.40.206.4 List of currently assigned Organic Peroxides in packagings
– 4.1.4 IBC520 – List of currently assigned self-reactive substances and organic peroxides in IBCs
– 220.127.116.11.6 T23 – List of currently assigned self-reactive substances and organic peroxides in in tanks
For full details on temperature controlled shipments of Dangerous Goods refer to Chapter 7.3 of IMDG Code.
While shipping dangerous goods in Reefers always remember that the “Reefer is a source of ignition”!