Hurricane Harvey made landfall in southern Texas on 25th August 2017 causing extensive damage and 48 fatalities. Chemical plants in the area were mostly shut down prior/during landfall.
Arkema plant at Crosby experienced power outage due to flooding and disruption of power to temperature controlled organic peroxides stored there. As the temperature began to rise these organic peroxides started exothermic self-accelerating decomposition. On 31st August two explosions and release of black smoke were noticed at the site. Thursday morning one trailer loaded with organic peroxide caught fire. 1.5 miles evacuation perimeter was maintained around the plant.
Following the incident U.S. Environmental Protection Agency deployed ASPECT (Airborne Spectral Photometric Environmental Collection Technology) aircraft to secure chemical information from the smoke cloud.
See how ASPECT aircraft works in below video
What are temperature controlled substances?
Certain chemicals, such as organic peroxides and self-reactive substances, need constant controlled temperature for safe storage, if temperature rises above certain limit a self-accelerating decomposition, possibly of explosive violence, may result.
Self-accelerating decomposition temperature (SADT) means the lowest temperature at which self-accelerating decomposition may occur for a substance in the packaging as used in transport.
How are temperature controlled substances transported?
Temperature controlled substances are transported with two temperatures in consideration.
- Control Temperature (Temperature maintained during transport), and
- Emergency Temperature (If the temperature of reefer container reaches this temperature emergency measures must be initiated)
These substances will always be transported in refrigerated containers. The mandatory requirement of refrigeration during transport is stipulated by IMDG Code with stowage code SW3 “Shall be transported under temperature control” in column 16a of Dangerous Goods List in chapter 3.2
How Control and Emergency Temperature is decided?
First step is to determine the SADT of the product as packaged for transport in accordance with guidance given in the Manual of Tests and Criteria part III, 32.4. When SADT is determined control and emergency temperatures are set as per below table.
If SADT of an organic peroxide in single packaging is 15 Deg C then control temperature is -5 Deg C (20 Deg C below SADT) and Emergency Temperature is +5 Deg C (10 Deg C below SADT)
Below sections of IMDG Code lists down currently assigned self-reactive substances and organic peroxides including those require temperature control during transport.
- 22.214.171.124.2.3 List of currently assigned self-reactive substances in packagings
- 126.96.36.199.4 List of currently assigned organic peroxides in packagings
- 4.1.4 – IBC 520 – In Intermediate Bulk Containers
- 188.8.131.52.6 – T23 – In Tanks
Refrigeration system for temperature controlled substances
Depending on the control temperature IMDG Code require single or dual mechanical refrigeration system. For self-reactive substances (class 4.1) under UN Nos. 3231 and 3232 and organic peroxides (class 5.2) under UN Nos. 3111 and 3112 reefer unit must have dual mechanical refrigeration system, apart from the integral power supply unit, the two systems must be independent of one another and each system alone must be capable of maintaining adequate temperature control.
Packing of Reefer Container
- If packages having different control temperatures are packed in same reefer then all packages must be pre-cooled to avoid exceeding the lowest control temperature and the substances with the lowest control temperature must be stowed closer to the doors of the Reefer.
- If non-temperature-controlled substances are transported in the same reefer with temperature controlled substances, the package(s) containing substances that require refrigeration must be stowed close to the doors of the reefer.
Alarm for the Reefer
If the substance require control temperature below +25 Deg C then the reefer must be fitted with a visible and audible alarm. This alarm must be independent to power supply to the reefer and must be set at not higher than control temperature.
How information of such cargo is provided to Master of the Vessel?
Carrier or carrier’s agent must provide below to information to master
- Shipper must include Control temperature in °C and Emergency temperature °C in Dangerous Goods Declaration which will be included in manifest.
- Operating instructions for the refrigeration system
- Procedures to be followed in the event of loss of control and instructions for regular monitoring of operating temperatures
- Spare parts when required by IMDG Code Sections 184.108.40.206.2.3 ,220.127.116.11.2.4 and 18.104.22.168.2.5
What happens when control temperature is exceeded?
Special provision 923 of IMDG Code require mandatory checking of temperatures of reefers during voyage. If temperature exceeds control temperature due to malfunctioning or breakdown of reefer then Master will initiate control measure by either repairing the refrigeration machinery or increasing the cooling capacity (by adding liquid or solid refrigerants).
What happens if temperature reaches emergency temperature?
If above control measures fail and the temperature keeps rising and reaches emergency temperature Master will initiate emergency action either jettisoning the packages into the sea or flooding the container with water, this is why section 22.214.171.124 of IMDG Code states “If the doors of a cargo transport unit are locked, the means of locking shall be such that, in cases of emergency, the doors can be opened without delay”.
To know more about temperature controlled cargo ,refer to chapter 7.3 of IMDG Code.
Could this incident be avoided?
NO! We can understand the predicament of evacuated residents, that too after devastating effect of hurricane Harvey, but no one can stop exothermic decomposition of these substances if power for refrigeration cannot be restored. The only way is evacuating the area and let the product decompose and finish off itself. Were there ways to restore refrigeration? Only an investigation can tell us.
For safety in transport it is imperative all personnel involved in transport of dangerous goods to receive training. Requirement of training to shore side personnel is mandatory as per IMDG Code Chapter 1.3.
Officers and ratings on board vessels responsible for cargo handling is required to have received training as per STCW Code, as amended.
Read more about Crosby incident: