Analysis of the explosion in the high-pressure steam pipeline during the commissioning of the thermal power project at Hubei Dangyang Madian Gangshi Power Generation Co., Ltd

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This post was last edited by *nht1 on 2016-8-19 at 21:58. 1.jpg This article has been published on the headline section of the HaiChuan Chemical Industry Network’s WeChat official account. The views expressed here are merely personal opinions; they do not constitute a basis for accident analysis, nor do they serve as legal evidence or outcomes of arbitration. According to reports by news media and Jingchu Net on August 11, at around 3:20 p.m. that day, during the commissioning phase of the thermal power project operated by Hubei Dangyang Madian Gangshi Power Generation Co., Ltd., a high-pressure steam pipeline suddenly ruptured, resulting in the release of large amounts of high-temperature, high-pressure steam. This incident led to the death of 21 workers on duty and the injury of 5 others, 3 of whom suffered serious injuries. http://a4.qpic.cn/psb?/V130toNH3YOQ2Q/py.U8otBpFeV5QqbbLXwxoTr3ejbKNjDbsX8fMIIIBc!/b/dK8AAAAAAAAA&ek=1&kp=1&pt=0&bo=UQP2AQAAAAAFB4E!&t=5&su=5183257281&sce=0-12-12&rf=2-9 http://a1.qpic.cn/psb?/V130toNH3YOQ2Q/dDzx*lOKy6YgFGEFmD15vlLB7Y08PpPonq82BmASnjY!/b/dPgAAAAAAAAA&ek=1&kp=1&pt=0&bo=JgMHAgAAAAAFBwQ!&t=5&su=2104536049&sce=0-12-12&rf=2-9 Analyzing the accident scene from the photos taken there, two defects are evident: first, the distance between the site of the explosion and the DCS control room is very short; second, there is a design flaw in the wall facing the DCS room – it should not be a partition 120 mm thick with fixed glass windows. According to relevant standards, it should be a fireproof and explosion-proof wall with a fire resistance rating of level 1. Moreover, the entire DCS control room should have no windows, only two doors, essentially functioning as a bunker. How powerful is high-pressure steam? Steam is, strictly speaking, a gas, and high-pressure steam can be considered as gas that has been compressed under high pressure. According to other reports, the temperature of the steam at that time was as high as 600°C, with a pressure of 24 Mpa; such conditions represent a supercritical state for water, which makes it extremely dangerous. So just how powerful is steam in this supercritical state? To understand this, let’s first look at the power of compressed air. We live in an environment filled with air, and oxygen in the air is essential for sustaining life. However, compressed air (or other compressed gases) possesses tremendous energy, and in the event of a failure in containers or pipes, it can cause severe damage and losses. The following 3 images show the scenes after 3 explosions, all of which occurred during pressure tests on pipes and containers. http://a4.qpic.cn/psb?/V130toNH3YOQ2Q/fYf5VsrVr4KImOhx.wECvOouJtXE.wCgPhtjUlXuJg4!/b/dK8AAAAAAAAA&ek=1&kp=1&pt=0&bo=RQGqAQAAAAAFB8s!&t=5&su=53858673&sce=0-12-12&rf=2-9 Figure 1 shows the situation that occurred during a pressure test on a pipe with a diameter of 36 inches (about 1 meter): a failure in the connecting flanges resulted in 1 death, 15 injuries, and severe damage to the equipment. At that time, the pressure of the compressed air was approximately 1,800 psig (about 12.41 MPa). Figure 2 shows what occurs during a pressure test using compressed air on the connection pipes of the storage tank. No blind plates or other effective and reliable isolation measures were taken before the test; instead, the storage tank and pipelines were isolated by simply closing the valves. Due to valve leakage, the compressed air from the test entered the storage tank, causing pressure to build up in it. The storage tank flew up like a rocket and eventually landed on the process pipe rack! In the accident shown in Figure 3, although nitrogen (rather than air) was used as the compressed gas, the consequences of the explosion were similar to those with air. During a pressure test using nitrogen, a pipeline failed, resulting in the death of 1 worker and severe injuries to 3 others. The above three cases all illustrate one issue: the destructive power resulting from the release of compressed gas. It’s not difficult to imagine what happens in such a moment of loss of control; those who have seen Jeong Bo-kun’s Eighteen Dragon Palms can immediately grasp just how great the destructive force is at that time. http://a2.qpic.cn/psb?/V130toNH3YOQ2Q/eDTA1I2vh7PKOHErPx8qMfZUP5ymct6xnf3K00pTo1Q!/b/dOUAAAAAAAAA&ek=1&kp=1&pt=0&bo=yAC0AAAAAAACB18!&su=3112173697&sce=0-12-12&rf=2-9 Here is another excerpt from the novel to help readers understand better: Ye Wenhui said, “I get it now. Thank you, Sister Liu; you truly are an expert – you know so much.” ” Liu Meng said, “Stop joking. When you write the dedicated section on safety facility design, you can explain it in this way.” When setting conditions for the architectural team, there is another issue to keep in mind: on your overall layout, you have designated both the propane filling facility and the filling facilities for other gases as a single building. Of course, we have done the same in the past. When specifying these conditions, it is necessary to state that firewalls must be installed between each filling facility; in other words, their fire resistance rating must be greater than three hours. In addition, when setting up the busbars, an explosion-proof wall should be used to isolate the gas cylinders from the gas shut-off valves. The location where this explosion-proof wall will be installed must also be communicated to the architectural team – don’t forget that. ” Ye Wenhui said, “I can’t forget it; they were shown on the old drawings. It took me a long time to figure out what those things were. Those filling stations looked like bunkers.” ” Liu Meng said, “Although propane is flammable and explosive and seems relatively dangerous, compared to propane, those other gases are even more hazardous.” At a pressure of 15 MPa, if there is a leak, the force generated can be enough to collapse ordinary walls. When you receive the safety assessment report, you can take a look at the physical explosion shock wave simulation analysis conducted as part of that assessment; if there is a large gas leak and no blast walls are in place, people within 5 meters are almost certainly not going to survive. ” After hearing Liu Meng’s words, Ye Wenhui was shocked to the point of gaping his mouth wide. He could imagine high-speed air currents shooting in all directions; once the filling station was built, workers would have to work there throughout the year. If anything went wrong due to poor design, not to mention holding the designers accountable, even just the weight of conscience would be unbearable. On his way back from Liu Meng’s place, Ye Wenhui made up his mind that in the future he would have to give careful consideration to safety measures when designing projects. As a chemical engineering designer, designing a project might just be considered work for him, but for the workers on site, it could very well be a matter of survival. Putting oneself in their shoes, there was no room for any carelessness. Victim analysis: First and foremost, we extend our condolences to those who lost their lives in this accident! Judging from the situation at the scene, the main victims of this accident were the control room operators. The incident occurred in the afternoon, outside of the shift change time, and as many as 29 people were present. For a plant of this scale, there shouldn’t be that many DCS control room operators – at most around 10. During testing, the other people present are usually those involved in the testing process, including engineers, personnel from equipment manufacturers, technicians, field operators, supervisors, and company executives. In fact, executives don’t necessarily need to be on site, unless they want to watch what’s happening or assert their authority. The predicted causes and responsibilities for the accident – as for the direct causes – may include design defects, material defects, the absence of an explosion-proof wall between the DCS room and the source of danger, an excessive distance between them, and the fact that the DCS room was not designed in a \"bunker\" style. It is possible to check by comparing with the drawings and relevant specifications. The possible indirect causes include the following: it may be due to excessive operating pressure, failures in the safety pressure relief devices, malfunctions in the interlock protection systems, or inadequate or failed pressure testing. Safety management is inadequate; emergency plans and measures for testing are insufficient; on-site inspection and acceptance procedures are not strict enough; and the validation of testing procedures is not thorough. The primary responsible parties are the design team, including designers, reviewers, approvers, those in charge of specific tasks, project managers, legal representatives, supervisors for manufacturing or installation, safety officers, as well as local regulatory authorities. The design team is not only guilty of illegal design practices; such actions constitute violations of the law and should be treated as such, with the relevant individuals facing criminal liability. These are merely personal analyses and do not represent legal judgments. Similar cases can be found on the website in Wuhai, China, where there is an example designed by Chengda – a typical accident resulting from design mistakes. To avoid similar situations, it is necessary to follow specifications, standards, regulations, and management rules strictly (such as building codes, petrochemical regulations, safety laws, and regulations on work safety in construction projects), conduct thorough HAZOP assessments, carry out standardized tests, assign clear responsibilities, and proceed with commissioning activities in a way that includes contingency plans, safeguards, measures, and preventive actions. How can individuals at work avoid the hazards posed by steam? They should learn to identify and assess potential danger sources in the workplace, stay aware of them, maintain a safe distance, avoid violating safety rules, wear appropriate personal protective equipment, stay away from high-pressure steam pipes, and keep a distance from high-pressure steam! How should a DCS room in such high-risk environments be designed? See the image for details; no explanation needed: http://a4.qpic.cn/psb?/V130toNH3YOQ2Q/XGz1oglVg7qG7Uf1C3sY0XQy9yXg7QAMtYXnR73Cx9o!/b/dAcBAAAAAAAA&ek=1&kp=1&pt=0&bo=iAFLAQAAAAADB.E!&su=5267250577&sce=0-12-12&rf=2-9. PS: Characteristics of the steam pipeline: large diameter, thick appearance (with insulation layer); it is covered with insulating material, painted red on the outside, with yellow polyurethane foam wrapped in PE; it has zigzag bends (square compensators), is covered with shiny electroplated iron sheet or aluminum foil (as a reflective insulation layer), has expansion joints (sleeve compensators), and includes drainage devices (drain valves); there is heat (radiant heat) nearby.