Explosion of a Flammable Mixture in a Petrochemical Plant
The incident occurred in a catalytic reforming unit. At 13:41, a leak occurred at the 90 elbow of a pressure pipe containing a mixture of hydrogen and naphtha. This pipe was located between the pre-hydrogenation heat exchanger and the pre-hydrogenation product tower heat exchanger. The flammable material leaking from the pipe burst into flames, and at 13:51 and 14:21 there were two more explosive combustions. Some of the nearby towers, pipelines and other equipment and facilities affected by the following high temperature flames continued to burn, with varying degrees of damage or rupture and leakage of combustible materials. The intensified combustions and fire triggered two subsequent deflagrations, 10 minutes and 40 minutes later respectively, after the first explosions.
Event Date
January 14, 2020
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause of the pipe rupture was corrosion. Due to corrosion, the wall thickness of the pressure pipe 90 elbow had become thinner and ruptured under an internal pressure of 0.2 MPa with an opening of about 950mm 620mm. The hydrogen gas mixture ejected to form an explosive mixture. The friction between the ejected gas and the pipeline generated electrostatic sparks, which triggered a fire.Regarding the root technical causes, the affected pipeline was continuously in an acidic environment. The company was not monitoring and analyzing the acidic water in the pre-hydrogenation tank. The continued recycling of this acidic water led to increasing concentrations of H2S, HCl and NH3 and intensified the corrosion of the pipeline.A contributing cause was the temperature of the pipeline. The operating temperature of the affected pipe was supposed to be 150C, and the design temperature was 170C. However, the actual operating temperature of the pipeline at the time of the accident was about 180C, and this accelerated the corrosion process. The investigation found also organization causes in the failing of implementing preventive safety measures (see below at lesson learned).
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
reforming unit, pressure pipe
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Currency
Lessons Learned
Lessons Learned
The investigation revealed sever shortcoming in the definition and execution of safety measures for the site:(1) The safety management system of special equipment was not implemented, in particular the part related to corrosion monitoring and prevention. The operator did not execute the annual thickness measurement procedures. Also, they did not realise that measurements performed previously by an external inspection were demanding corrective actions. (2) The procedures for the analysis of acid water quality were not well designed and not implemented. (3) The pressure pipeline were not respecting the requirements of the more recent regulations, and therefore, de facto, illegal. (4) The operator did not perform the regular (annual) inspection of all the special equipment on site.
Event Nature
Emergency Action
The municipality safety department intervened with 49 fire trucks and 121 firefighters. They acted according to the strategy: first control, then elimination, and "cooling and suppressing explosions, focusing on protection, and preventing spread", using equipment such as fire-fighting robots and mobile fire-fighting water cannons. The public security department dispatched 628 police officers to implement traffic control and maintain order at the scene. The health department dispatched 5 ambulances to stand by on site. Approximately 5 hours later, the fires were completely extinguished.
Release Type
Release Substance
Release Pressure (bar)
0.20
Hole Length (mm)
950
Hole Width (mm)
620
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Investigation report available at
http://www.zhuhai.gov.cn/yjgl/gkmlpt/content/2/2608/mpost_2608730.html?…
(last retrieved 20.02.2023)
B.Wang et al., Hydrogen related accidents and lesson learned, submitted to ICHS-2023