【Safety Story】Complacency Nearly Causes Disaster

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On a cold, snowy winter day in 2009, with bitter winds blowing, the flow rate in the reflux line at the top of the acid water stripping unit where I was working began to drop rapidly, and it became difficult to keep the temperature at the top of the stripping tower within the required range. The operators initially concluded that the reflux line at the top of the tower might have frozen. As the production supervisor, I promptly led the team members to conduct an on-site inspection to confirm that the reflux line at the top of the tower had frozen, and immediately organized the staff to start thawing it. The outdoor temperature was over minus 20 degrees at that time, and facing a stripping tower over 50 meters tall, the colleagues were at a loss as it was very difficult to fully thaw it, especially under such harsh weather conditions; this task was extremely challenging. However, in order to thaw as quickly as possible and resume normal production, the colleagues pooled their ideas and suggestions, dividing into 3 groups to carry out steam purging for thawing in stages. Once the plan was finalized, everyone stepped in actively: they connected the steam purging lines, transported belts to the tower, and launched a full-scale effort to deal with the thawing pipelines. On that bitterly cold day with howling winds, from 8 a.m. to 4 p.m., my colleagues stayed on those towers standing dozens of meters high, holding onto steam belts as they climbed up and down; their bodies were covered in hard ice, their hats had thick layers of frost on them, and their hands were red from the cold. Yet they didn’t complain or show signs of fatigue, fighting bravely at the front line of the thawing effort. At around 3 p.m., there seemed to be signs of some improvement in the blocked pipeline, so liquid was drained from the end discharge point to check the progress of thawing the pipeline. At that time, the risks associated with venting residual liquids had been identified; the toxic and harmful hydrogen sulfide-rich gases inside the tower could be released through the pipelines, posing a risk of poisoning and asphyxiation. One employee volunteered to check the venting pipeline, but out of fear of hassle and a desire for convenience, he took no protective measures; he held his breath, entered the factory building, and opened the venting valves. The moment the valve was opened, a gas containing hydrogen sulfide was released, and the alarm went off. He immediately closed the valve and left the factory building; at that point he already felt somewhat suffocated, and it took some time for him to recover. Seeing their colleague out of breath, all the employees present were terrified and broke into a cold sweat. Everyone conducted a thorough reflection on this false alarm incident: **the standards allow a hydrogen sulfide concentration in the air of no more than 10 mg/m3; high concentrations of hydrogen sulfide (1000–2000 mg/m3) can cause instant death. The upper range of the hydrogen sulfide detector is 200 mg/m3, and at that time the hydrogen sulfide concentration on site had already exceeded 200 mg/m3. If that employee were unable to hold their breath for that duration, a poisoning incident would occur, with consequences that are unthinkable. Before entering the factory building, if safety procedures are followed strictly, by wearing a hydrogen sulfide detector and a positive-pressure air respirator and conducting a thorough inspection at your own pace, there will be no unnecessary alarms. Although several years have passed since that incident, the profound lessons learned remain vivid in my mind, constantly reminding me that safety work cannot allow any carelessness or slackness. Failing to strictly follow rules and regulations, and seeking shortcuts to save time, are the causes of accidents.