【Haichuan Sharing】Shocking! ! ! Various pipeline corrosion incidents

(1) Direct cause of the accident Through investigation, as well as technical analysis, testing, and evaluation, it was determined that: 1. The direct cause of the deflagration was the rupture of a 90° elbow in the pressure pipeline (250P2019CS-H), located between the feed/product heat exchanger E202A-F of the catalytic reforming unit and the feed heat exchanger E204AB of the pre-hydrogenation product/dehydration tower. Corrosion had thinned out this elbow, leading to its rupture (the rupture area was approximately 950mm×620mm). The naphtha-hydrogen mixture under pressure (2.0 MPa) inside the pipeline burst out, and when it mixed with air, an explosive mixture was formed. Static electricity generated due to friction between the escaping medium and the pipeline triggered the deflagration. 　　2. Reasons for the intensified and ongoing deflagration: Some of the nearby towers, pipelines, and other equipment were damaged or ruptured to varying degrees due to the continuous heating by the high-temperature flames; the leaking flammable materials exacerbated the burning and spread of the fire, leading to two further deflagrations. 　　3. The main cause of the rupture in the pressure pipeline is abnormal corrosion of the pipeline: (1) The pipeline involved in the accident was continuously exposed to an acidic environment, which accelerated its corrosion. Changlian Petrochemical Company failed to conduct continuous monitoring and analysis of the acidic water in the pre-hydrogenation high-pressure tank V202, which contained H2S, HCl, and NH3 generated as a result of the pre-hydrogenation reaction; as a result, this acidic water was continuously reused, leading to an increasing concentration of substances such as H2S, HCl, and NH3 within the pipes, thereby accelerating pipe corrosion. 　　(2) Pipe temperatures exceeding design limits exacerbate pipe corrosion. The intended operating temperature of the pipeline involved in the accident was 150°C, with a design temperature of 170°C; however, at the time of the incident, the actual operating temperature of the pipeline was around 180°C, which exceeded the designed operating temperature for that pipeline. In a wet H2S, HCl, NH3 composite acidic environment, excessive operating temperature of pipelines exacerbates pipeline corrosion.

On August 15, 1987, an explosion occurred at the JU'AYMAH gas processing plant in Saudi Arabia. Earlier in the incident, the natural gas plant experienced several power outages due to electrical failures, and these interruptions caused one or two natural gas fractionation production lines with a capacity of 165,000 barrels per day to stop operating. The units of these two distillation production lines are arranged in parallel, 100 feet apart from each other. During the power outage, the propane feed rate was approximately 100% of the design capacity of Unit 1 and 25% of the design capacity of Unit 2. It is understood that within 30 minutes, Unit 1 released approximately 1,900 barrels of propane. A leak occurred at the flange of a 4-inch diameter valve on one of the pipelines in the plant where the accident took place, resulting in a propane leak ； When propane leaked, it formed a large cloud of vapor; a car parked at the scene, ready to be restarted, ignited that vapor cloud, resulting in an explosion.

On August 15, 1984, a fire broke out at a synthetic bitumen sand plant in Fort McMurray, Canada. Course of the incident: At 21:30 on the evening of August 15, in a fluidized-bed coking unit with a capacity of 82,000 barrels per day, an erosion-induced failure occurred in a 10-inch diameter slurry circulation oil pipeline. This led to the release of 86 barrels per minute of heat-recovered slurry and asphalt at a temperature of 374 degrees Celsius (nearly the auto-ignition temperature). The resulting vapor cloud ignited almost immediately, causing a large-scale ground fire that resulted in the failure of six or seven additional systems. The fire that followed got out of control and burned for two hours. The fire eventually spread over an area with a diameter of 150 feet, and the damage to the modular structure reached over 100 feet. The reactor distillation column, light diesel stripping tower, 15,000 horsepower blower, pumps, and pipe racks were severely damaged or destroyed. During the fire, in addition to the pumps that could not be turned off and which exacerbated the blaze, approximately 2,700 barrels of hydrocarbon liquid flowed out from the damaged process equipment. The steam pipeline providing 6.2 Mpa of turbine-driven steam to the compressor burst, hindering the firefighting efforts. At 1:20 a.m. on August 16, the fire was extinguished.

Cause of the accident: 1. The rupture occurred at the bottom of the pipe; due to thermal sulfidation corrosion, the wall thickness of the pipe decreased to 0.96 millimeters (originally 7.1 millimeters). 2. Equipment management is not standardized. There is a lack of labeling for pipeline materials and routine tracking and monitoring. Poor management during the pipeline’s production shutdown. 3. Lack of change/risk management, resulting in the failure to identify key risks. 4. Lack of appropriate operating procedures, such as a safety work permit system. 5. There was no adequate investigation into the capabilities of the maintenance contractors, and worker training was insufficient, preventing them from handling related incidents. 6. Communication errors with the contractor.

At around 6:42 on June 13, 2021, a gas explosion occurred at the market in Yanhu Community, Zhangwan District, Shiyan City, resulting in 26 deaths and 138 injuries. Immediately following the accident, **** issued important instructions, ordering that every effort be made to rescue the injured, that measures be taken to comfort the relatives of those who lost their lives, that the cause of the accident be determined as soon as possible, and that those responsible be held accountable strictly. **The Prime Minister and other central leaders issued directives, setting requirements for emergency rescue efforts, the treatment of injured persons, and investigations and handling of the situation. **Working groups dispatched by the Ministry of Emergency Management, the Ministry of Housing and Urban-Rural Development, and the National Health Commission went to the scene to provide guidance. The State Council’s Safety Committee took charge of overseeing the matter and dispatched a supervision team to provide on-site guidance for the accident investigation. The Hubei Provincial Party Committee and the provincial government attached great importance to this matter; Ying Yong, the secretary of the Provincial Party Committee, gave immediate instructions, coordinated efforts via video conference, and went to the scene to oversee the rescue operations. Wang Zhonglin, Deputy Secretary of the Provincial Party Committee and Governor, rushed to the scene on the day of the incident to organize rescue efforts and other related activities. The provincial Party committee and the provincial government established an accident investigation team headed by the members of the provincial Party committee’s leadership team and the executive vice governor, and invited experts in areas such as gas pipeline design and operation, fire safety, special equipment, and safety measures from across the country to participate in the investigation. Upon investigation, the direct cause of the accident was severe rusting and rupture of the medium-pressure natural gas pipeline. The leaked natural gas accumulated in a confined space in the river channel beneath the building, and an explosion occurred when it came into contact with sparks from the exhaust pipes of food businesses. The accident also exposed issues such as hidden dangers arising from illegal construction, the failure to identify and address these hazards over time, chaotic property management, and inadequate on-site emergency response. This accident is a serious liability incident in production safety.

At around 6 a.m. on January 25, 2021, an explosion occurred near Jin Bohai Jing in Youyi Sub-district, Jinpu New Area, Dalian. The initial assumption is that the explosion was caused by a leak in the gas pipeline belonging to Jinzhou Tiancheng Gas Company. To date, the accident has resulted in 3 deaths and 8 people suffering minor injuries. At 8 p.m. on July 16, 2007, the Gas Management Office in Hanyang District, Wuhan, received a report from the natural gas company indicating that there were abnormalities in the pipelines in the Qingshiqiao residential area. Through systematic inspection by the line patrol personnel, the leakage point was found in a sewage well in front of Building 3 in the Qingshi Bridge residential complex. On-site inspections revealed that this sewage well was built atop a gas pipeline, with sewage soaking the pipeline for an extended period; as a result, the pipeline, unable to withstand the corrosion, became damaged and started leaking. At around 11 a.m. on April 10, 2016, security inspectors from Sinopec Jinhong Natural Gas Company, which is under the jurisdiction of the Zhangjiakou Urban Management Bureau, discovered during their safety inspections that the gas main in the industrial workers’ residential building on Jianshe East Street in Qiaodong District was corroded and leaking gas. Upon arriving at the scene, the emergency repair team inspected the area and found that the main gas pipeline in the customer’s home was located about 50 centimeters away from the sink; moreover, the sink had been leaking water, which over time led to corrosion of the pipeline. On-site repair personnel sawed off the corroded pipes and replaced them with new ones, without disrupting the normal use of the kitchen. In 2008, when Wenzhou Pipeline Gas Company was conducting routine inspections of a certain section of pipeline, it detected a gas leak. As more gas leaked out, its concentration in the air reached the lower limit for explosion. After excavating the road surface, it was found that the gas pipeline had corroded, with a leak site the size of a grain of rice on it. It is presumed that the anti-corrosion coating of the pipeline was damaged during the installation of other pipelines, leading to corrosion of the pipeline.

After removing the oil sheets and rust from the surface of the attached pipes, the gas pipeline was found to be corroded and perforated

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