美国田纳西州海格纳士公司铁粉爆炸

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事故简况

事故1

事故2

事故3

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事故过程

2011年1月31日爆炸事故

2011年1月31日,事故发生时,两个夜班机修工在检修发生跑偏故障的斗式提升机。该提升机位于退火炉的下游, 用于将细铁粉输送到成品仓。 当时两个工人各自站在斗式提升机的平台上。提升机启动的时候,扬起了粉尘。粉尘被点燃,将两名工人烧伤。该斗式提升机的除尘系统在两天前出现故障,该故障导致了这次事故。

The first incident occurred on January 31 as two maintenance mechanics on the overnight shift inspected a bucket elevator that had been reported to be malfunctioning due to a misaligned belt. The bucket elevator, located downstream of an annealing furnace, conveyed fine iron powder to storage bins. The two mechanics were standing alone on an elevated platform near the top of the bucket elevator, which had been shut down and was out of service until maintenance personnel could inspect it. When the bucket elevator was restarted the movement immediately lofted combustible iron dust into the air. The dust ignited and the flames engulfed the workers causing their injuries. A dust collector associated with the elevator was reported to have been out of service for the two days leading to the incident.

2011年3月29日爆炸事故

2011年3月29日,一个工程师在更换炉子的点火器时被烧伤。当时他不小心碰落了沉积在炉子上方平面上的铁粉尘。

The second incident occurred less than two months later on March 29 when a plant engineer, who was replacing igniters on a furnace, was engulfed in combustible dust which ignited. In the course of the furnace work, he inadvertently dislodged iron dust which had accumulated on elevated surfaces near the furnace. He experienced serious burns and bruises as a result of this second event; a contractor witnessed the fireball but escaped without injury.

2011年5月27日爆炸事故

5人受伤,其中3人生命垂危。根据公司官员的说法,事故发生在一个炉子附近。2011年6月3日CSB召开了新闻发布会通报了调查结果。

An explosion was reported earlier today at the plant, injuring five, including three who were in critical condition at the Vanderbilt University Medical Center burn unit in Nashville.According to a company official, today’s accident took place in the vicinity of one of the facility’s furnaces.

2011年6月3日 CSB召开新闻发布会

Rafael Moure-Eraso(新闻发布会主持人):

今天,我们为大家带来了2011年5月27日海格纳士公司铁粉爆炸事故调查的最新消息。很遗憾,本次事故2名工人死亡,1人重伤。

CSB对采自现场的粉尘进行了广泛的测试。测试表明,1月和3月爆炸事故后现场采集的样品时可燃的,并能在测试条件下爆炸。

沉积的(尤其是沉积在高处表面的)可燃粉尘是工作场所的重要危害。自从化学危害调查委员会(CSB)1998年成立以来,4起最严重的爆炸事故中有3起是粉尘爆炸事故。

很多常见的可燃物质在以粉尘状态出现的情况下是可以爆炸的,例如金属、木材、煤。面粉、糖、塑料和其它的化学品和药品。

Rafael Moure-Eraso (Chairman of News Conference):

We are here today to update the media and the public on the status of our ongoing investigation into the explosion and ensuing fire that occurred at the Hoeganaes facility on Friday, May 27 in Gallatin, Tennessee. Tragically, two workers died and a third was gravely injured.

CSB and its experts have done extensive testing on the metal dust from the facility. Tests show that powder samples collected from the sites of both the January and March accidents were combustible and could be exploded under test conditions.

Combustible dust is an insidious workplace hazard when it accumulates on surfaces, especially elevated surfaces. Since the CSB was established in 1998, three of the four deadliest accidents we have investigated were determined to be combustible dust explosions.

A wide range of common combustible materials can explode in finely powdered form, including metals, wood, coal, flour, sugar, plastics, and many chemicals and pharmaceuticals.

Johnnie Banks(CSB负责该事故的调查组长):

该工厂收集废铁,熔化并雾化为铁粉,然后在氢气燃烧的大炉子中退火,然后研磨、打包作为成品卖出。

在CSB对海格纳士公司的3次现场调查中发现了事发地点附近沉积了大量金属粉尘。金属粉尘的闪爆比可燃气体和可燃蒸气火灾产生更大的烧伤危害。金属粉尘的燃烧产生更多的热和辐射,有些金属粉尘的燃烧火焰的温度非常高,远高于其他可燃物质。现场调查处理观察到空气中的悬浮粉尘,在建筑和设施的表面、椽子和栏杆上看到厚达2~3英寸的金属粉尘层。

根据对目击者的问询,事故发生在2011年5月27日上午6时30分和6时40分之间。大约在6时10分,2名退火工艺操作工人听到输送氢气、氮气和冷却水的工艺管道沟中发出嘶鸣。听到嘶鸣后,他们叫来工厂维修工揭开估计发生嘶鸣的管道的上方的盖板。

在试图用撬杠打开管道沟的盖板几次不成功后,他们打电话召来了叉车。盖板通过铁链挂在叉车上拽起。在盖板被撬起后,爆炸发生了。有目的者看到了闪光,有人听到了爆炸的闷响并感到了建筑物的摇晃。建筑内充满了粉尘,爆炸的火光传到了室外。有目的者看到了从上往下掉落的燃烧的粉尘。

我们现在已经知道,初始爆炸是氢气泄漏到管道沟导致的。尽管如此,现场目击者的证词和物理证据均表明铁粉参与了爆炸。

Johnnie Banks (Team Lead, the investigator-in-charge for this case):

Briefly, the plant collects scrap iron, which is then melted, sprayed into powder form, and then annealed using hydrogen gas using a large continuous furnace. This powder is then further milled, packaged, and eventually sold as a final product.

During all three of our trips to the Hoeganaes plant my team observed alarming quantities of metal dust within close proximity to the incident locations. This was of particular concern as metal dust flash fires present a greater burn injury threat than flammable gas or vapor flash fires. Metal dust fires have the potential to radiate more heat and some metals burn at extremely high temperatures in comparison to other combustible materials. In addition to visible dust particles in the air, 2 to 3-inch layers of dust were observed on flat surfaces, rafters, and railings throughout the facility.

According to witness interviews the incident took place on Friday, May 27, 2011, between 6:30 and 6:40 am. At about 6:10 am, two annealing operators heard a hissing sound in a trench that housed a number of process pipes carrying hydrogen, nitrogen, and cooling water. When the operators heard the hissing sound, they summoned plant maintenance personnel to lift a cover over the area where the gas leak was thought to have occurred.

After several attempts to lift the cover with a pry bar were unsuccessful, a call went out to get a forklift. The cover was attached to the forklift with a metal chain and raised. As the cover was pried opened, an explosion occurred. Some witnesses saw a flash of light; some heard a muffled boom and felt the building shaking from the explosion. The building filled with dust and the lights went out. Witnesses saw burning dust raining down from above.

The initial explosion, we now know, involved hydrogen gas that had been leaking into the trench from a large hole in the vent pipe. However, the witness statements as well as the physical evidence leave no doubt that combustible iron dust was also involved in the aftermath of the explosion.

调查进展

2011/02/16:  CSB Continues Investigation of Fatal Fire at Hoeganaes Corporation Located Outside of Nashville, Tennessee

2011/05/11: U.S. Chemical Safety Board Continues Investigation of Two Accidents at the Hoeganaes Corporation Facility

2011/05/27: CSB Deploys to a Third Accident at Hoeganaes Corporation Metal Powder Plant in Gallatin, Tennessee

2011/06/03: Statement for the news conference

铁粉爆炸实验视频,2011年5月26日录制(美国化学安全与危害调查委员会CSB提供)

该爆炸实验录像采用的粉尘取自海格纳斯公司2011月1月31日发生爆炸的车间。录像包括两次测试。并分别以常规速度和低速方式播放。

下载视频

背景知识

海格纳士公司

海格纳士公司是全球领先的铁基粉末制造商,产品广泛应用于全球的粉末冶金、化工及焊接等产业。 事发工厂有175名员工,主要生产雾化铁粉,销售给汽车和其他行业用于粉末冶金方法生产金属零部件。

美国化学安全与危害调查委员会(CSB)

美国化学安全与危害调查委员会(CSB)是美国联邦的独立机构,主要职能是调查重大化学安全事故。其成员由总统提名,在参议员表决通过。CSB调查化学安全事故的所有方面,包括设备故障在内的自然原因(physical causes),也包括规章制度、工业标准和安全管理系统等方面的不足。在事故调查之后,CSB不负责褒奖和惩罚,而是向工厂、工业机构、工会(labor groups)和美国职业安全与健康管理局和美国环保局等法规制定机构提供建议。CSB的事故调查报告可通过 www.csb.gov 获取。

铁粉的爆炸性参数


东北大学工业爆炸及防护研究所
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