In this episode of the Dust Safety Science Podcast, we are speaking with Ali Alnajdawi, fire investigator at Forensic Laboratory Department and electrical engineer with the Ministry of the interior of Jordan, about the large grain silo explosion that occurred at Port Aqaba in 2018.
At the time of recording, we are analyzing the data for our year-end incident report, and this explosion appears to be the most devastating confirmed dust explosion in 2018. The Port Aqaba incident took the lives of seven workers and injured several more. Ali was involved in the subsequent investigation and in this interview we discuss:
- The causes leading up to this incident?
- Where did ignition occur and how did that propagate throughout the facility?
- What processes are being put into place to avoid this type of incident in the future
An Overview of the Port Aqaba Grain Silo Explosion
On May 14, 2018, old silos at a grain storage terminal were being emptied and dismantled at Port Aqaba, Jordan. The terminal had 75 silos, each one forty-five meters high and nine meters in diameter. Each silo could hold 200,000 tons of wheat.
Next to the silos was a fifty-five-meter tall tower that contained a grain conveying system including bucket elevators. The bucket elevators and conveying system ran down to underground tunnels containing a horizontal conveying system and relevant structures and machinery for transporting the wheat from the silos into the road trucks.
The property owners, Aqaba Development Corporation, had emptied the silos and transported most of the wheat to a new location. The dust suction systems were also dismantled, the electricity cut off, and the Abu Ghraib company was commissioned to demolish the silos using one ton of dynamite and time delay capsules.
This subcontractor had received a risk assessment report alerting them to the risk of the dust explosion and the need to clean the silos before work commenced. According to Ali’s investigation, they did not comply and a dust explosion occurred during the decommissioning, killing seven Jordanian workers in total.
Below are some site photos that Ali has supplied showing the destruction caused by the series of explosions.
After an investigation, Ali Alnajdawi and his team concluded that the five main elements required for a dust explosion were present on the third floor of the tower, and in the grain conveying system:
- Dust (in this instance, wheat)
- A confined space (the conveyor system)
- Dispersion of the dust by workers or a primary explosion
- Oxygen in the air
- An appropriate ignition source
The ignition source was not determined, but Ali believed that it was a spark from iron being cut to place the dynamite. It triggered a combustible fire that quickly turned into a primary dust explosion. Then it spread into the underground tunnels, causing secondary explosions due to dust deflagration.
Lessons Learned From the Port Aqaba Incident
Ali said that two lessons were learned from this incident. The first involved the two serious mistakes made during this incident:
- The company dismantled the dust suction system and cut the electricity left wheat inside the silos, conveyors, pipes, and underground tunnels.
- The same contractor did not heed the warnings and went to work without cleaning the silos and removing the dust.
The second lesson addressed the safety procedures that should be used to prevent another combustible fire or dust explosion. Ali couldn’t locate any precedent for such cases in Jordan, so he referred to OSHA and NFPA codes such as well as the European standards related to dust safety to develop an action plan for future hazards at Port Aqaba.
Ali started by dividing the incident site into three zones according to hazard:
- Zone A (most dangerous): the tower and underground tunnels with all the confined spaces
- Zone B: the main silo columns, which were enclosed with small venting holes at the top and sides
- Zone C: The main silo columns with small venting holes at the top and sides but were partially demolished and nearly ready for demolition.
Each zone had different safety procedures and work steps to eliminate all the dust explosion risks, such as:
- Ventilation
- Vacuuming
- Housekeeping
- Dust washdown
- Ignition source control
The plan included:
- Specific explosion filter vacuums that were compatible with NFPA 70
- Using a water-spraying machine for dust washdown compatible with OSHA and NFPA 70
- Installing explosion-proof lights in dark places
Ali successfully implemented his plan and worked with a dedicated team to eliminate all combustible dust hazards at the site. You can read his report of the Port Aqaba incident here.
Ali’s Recommendations
Based on his investigation of the Port Aqaba incident, Ali recommended the implementation of a proper management system to minimize dust fire or explosion incidents. This could be accomplished by:
- Establishing an allowable official value for dust accumulation;
- Ensuring that the proper equipment is available for routine cleaning;
- Inspecting the areas where combustible dust could accumulate;
- Determining
frequency of cleaning; - Keeping dust suction system active during decommissioning and cleaning;
- Ensuring that personnel are trained on appropriate cleaning
techniques ; and - Preparing an awareness program to increase worker awareness of combustible dust hazards.
Ali compared a worker employed in a dusty place to an explosives expert who is trying to stop a time bomb: if he hits the wire, it would cause the bomb to explode. As he states many personnel who work in dust handling facilities have no awareness in this area, and that needs to change.
Conclusion
We were truly honored to interview Ali and hear his perspective on this tragic 2018 incident in addition to the lessons that he and his team learned. These insights from around the world bring us closer to our goal of developing systems and processes to avoid the combustible dust fires and explosions that so often end in tragedy. It is our hope that the lessons learned from this incident can be used to develop better approaches to grain silo explosion prevention and decommissioning of powder and dust handling facilities.
If you would like to discuss further leave your thoughts in the comments section below or you can reach out to Ali Alnajdawi directly:
Email: alialnajdawi84@yahoo.com
LinkedIn: Profile
Resources Mentioned
Dust Safety Science
Companies
Aqaba Development Corporation
Organizations
Standards
Incidents
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