23在敞口储罐中搅拌并加热易燃液体.docx

1、23在敞口储罐中搅拌并加热易燃液体CASE STUDYMixing and Heating a Flammable Liquid in an Open Top Tank One killed, two injuredInvestigation No. 2006-08-I-ILApril 2007案例研究在敞口储罐中搅拌并加热易燃液体1死两伤调查报告编号：2006-08-I-IL2007年4月1. Incident Description This Case Study describes the ignition of a vapor cloud generated by mixing and

2、 heating a flammable liquid in an open top tank without adequate safety controls. The tank was located in the chemical mixing area of the Universal Form Clamp (UFC) facility in Bellwood, Illinois, a suburb of Chicago. 1、突发事件概述该案例研究描述了在敞口储罐中搅拌和加热易燃液体时未采取足够的安全控制措施而导致易燃蒸气被点燃的事故。储罐位于芝加哥郊区伊利诺伊拜尔伍德的通用窗体夹（

3、UFC）工厂的化学反应场。On the morning of June 14, 2006, an operator was mixing and heating a flammable mixture of heptane and mineral spirits in a 2,200-gallon open top tank equipped with steam coils. The finished product, “Super Clean and Tilt,” is a proprietary mixture, which is applied to cured concrete su

4、rfaces to prevent bonding with wet concrete. As the operator was adding an ingredient to the batch, he observed a “dense fog” accumulating on the floor below the tank (Figure 1).2006年6月14日上午，操作员在配备有蒸汽管圈的2200加仑的敞口储罐中搅拌庚烷和矿物油精。成品是一种专用搅拌物，名称是“超级清洁和倾斜”，主要用于防止湿的混凝土粘结与已凝固的混凝土表面。操作员在向反应物中添加制剂时，他观察到储罐下的地板上积

5、聚了一股“浓雾”（图1）。Figure 1. Vapor spilling from top of mixing tank图1 搅拌储罐顶部蒸气泄漏He immediately notified a senior operator who helped him shut down the operation. They both exited the building and advised workers in adjoining areas to leave. As the vapor cloud spread throughout the mixing area and surround

6、ing workspaces, other employees exited the building (Figure 2).他立即通知资深操作员帮助他关闭了工艺系统。他们一起跑出了建筑并建议毗邻区域的工人们离开。随着蒸气云扩散到了整个搅拌区和周围的工作区，其他工人也离开了建筑（图2）。Figure 2. Vapor cloud propagation图2 蒸气云扩散Within about 10 minutes after the operator first observed the vapor cloud, most employees who were working in the a

7、rea had evacuated. A contracted delivery driver passed some of these employees as he walked into the building and into the spreading vapor cloud. The cloud ignited within seconds of him entering. The driver died several days later from the burns he received. 操作员发现蒸气云后的十分钟左右，在那个区域工作的大部分工人都已经撤离。承包商的一名

8、送货司机在进入蒸气云扩散区前碰到了一些离开的工人。他进去几秒钟后蒸气云被点燃。司机被严重烧伤并于数天后死亡。The pressure created by the ignition blew the doors open to an adjacent area, injuring a temporary employee. This employee suffered second-degree burns and was hospitalized for three days.The Bellwood Fire Department battled a fire confined to a

9、bagged resin storage area for about three and one-half hours. The fire and pressure from the initial ignition produced moderate damage to the structure and interrupted operations for nearly one month. UFC suspended the flammable liquid mixing operation indefinitely.蒸气云燃烧产生的压力将开着的门甩到了相邻区域，一名临时工受伤。这名临

10、时工被鉴定为二级烧伤，在医院接受了三天治疗。拜尔伍德消防部门用了三个半小时才扑灭了袋装树脂存储区域的火灾。初始燃烧的火势和压力致使建筑遭受中度损坏，并导致了将近一个月的生产中断。该公司无限期暂停易燃液体的搅拌操作。2. Physical Evidence 2.1 Materials Testing As the operator began adding L50 (a non-reactive liquid) to the mixture, he noticed vapor spilling from the top of the tank. To determine if the L50,

11、or any of the other ingredients, could have caused a reaction, independent laboratories tested the mixture and the individual ingredients. This did not identify any reactive materials, indicating that the concurrence of the vapor cloud and addition of the L50 were coincidental. 2、物证2.1材料测试当操作员向搅拌物中添

12、加L50（一种不参与反应的液体）时，他观察到储罐顶部冒出了蒸气。为了确定是L50还是其他配料引起了这一反应，需要进行独立的实验室试验来测试搅拌物及其每一种配料。试验结果也没有发现参与反应的物质，这表明出现蒸气和添加L50只是一个巧合。2.2 Tank Heating System Performance testing by a contracted testing firm verified that the boiler system, under normal operating conditions, delivered enough energy to boil the mixtur

13、e (221 F, 105 C), and there were no leaks in the steam coil inside the mixing tank. 2.2.1 Mixing Tank Temperature Controller The temperature controller consisted of a liquid-filled temperature-sensing bulb and a pneumatic control unit. It regulated the tank temperature by opening and closing the tan

14、ks heating coil steam valves. Because the controller was damaged by the explosion and fire, it was not tested to determine its operability. However, when CSB investigators examined the controller it was found to have not been installed or maintained in accordance with the manufacturers specification

15、s, which could have caused it to fail or perform erratically on the day of the incident. 2.2储罐加热系统由承包测试公司进行的性能测试证实了以下发现： 正常工作条件下，锅炉系统可以输送足够的能量来煮沸搅拌物（105C）； 搅拌储罐内的蒸汽盘管无泄漏。2.2.1搅拌储罐温度控制器温度控制器由液体填充的温度检测球和气动控制单元组成。它通过打开和关闭该容器的加热盘管蒸汽阀调控罐内的温度。由于控制器遭到爆炸和火灾破坏，因此它无法试验以确定其可操作性。然而，当CSB调查员检查控制器后发现，没有按照制造商的规格安装或

16、维护控制器，这也许才是事故当天控制器失效或者不稳定的原因。The following findings may explain how the temperature controller malfunctioned, and how the vapor cloud was created. The temperature-sensing bulb and thermometer well housing (thermowell) did not conform to the manufacturers specifications. The thermowell, designed to b

17、e filled with thermal conductive fluid, was dry, and parts designed to hold the bulb in place were missing (Figure 3). The bulb was not fully inserted into the well (Figure 4). Both of these conditions may have contributed to inaccurate temperature sensing or a delayed response, and may have caused

18、the steam valves to remain open long enough to boil the mixture. 以下发现也许可以解释温度控制器失灵和形成蒸汽的原因。 温度检测球和温度计以及外壳（温度计套管）不符合制造商的规格。（1）设计成填充导热液体的热电偶套管是干的，设计用来固定玻壳的部件不见了（图3）。（2）玻壳没有完全插入热电偶套管中（图4）。这两个条件共同导致了温度检测不准确或者延迟反应，也可能导致蒸汽阀长时间开启不断加热搅拌物。Figure 3. Temperature sensor well 图3温度传感器Figure 4. Intended sensor loc

19、ation图4传感器原本位置 There was a restrictive bend in the liquid-filled capillary tube connecting the sensing bulb to the temperature controller (Figure 4). Fluid inside the bulb must be able to expand and move freely through the capillary tube for the controller to operate properly. This bend may have cau

20、sed the controller to perform sluggishly or to malfunction. 连接感测球到温度控制器的液体填充毛细管上有一个严格的弯曲（图4）。感测球内的液体必须能够扩展并通过毛细管自由移动，以保证控制器正常运行。这种弯曲可能造成控制器执行缓慢或出现故障。 UFC did not filter oil or remove moisture from the “plant air” flowing through the temperature controller. Accumulated oil and/or water, or corrosion

21、caused by humid air may have prevented the controller from operating as designed, allowing the mixture to overheat. 该公司未对流过温度控制器的“工厂空气”过滤油气或除去水分。引起的潮湿空气积累的油和/或水或腐蚀性物质可能已经使控制器无法正常操作，并允许搅拌物过热。2.3 Temperature Measurement The process for making Super Clean and Tilt required several hours of mixing and h

22、eating. To begin heating, the operator manually opened the steam valves to the tank heating coils and adjusted the temperature controller to maintain the temperature at 164o F (73C). When the batch process was completed, the operator closed the steam valves and allowed the mixture to cool. 2.3测温生产成品

23、需要数小时的搅拌和加热。开始加热时，操作员手工打开加热盘管的蒸汽阀并调节温度控制器使之维持在73。这一批次的工艺完成时，操作员关闭蒸汽阀并让搅拌物自然冷却。The mixing tank was not equipped with a temperature display or high temperature alarm, and there was no backup shutoff device. The procedure for this mixture required the operator to verify the temperature by climbing the

24、stairs to the upper level to measure it using a hand-held infrared thermometer (Figure 5). If, after checking the temperature, the mixture overheatedas CSB believes occurred in this incidentthe operator would not know until the vapors overflowed from the tank.搅拌储罐没有装设温度显示器或高压警报器，也没有备用切断装置。该搅拌物的操作程序要

25、求操作员通过梯子爬上顶端并使用手持式红外测温仪测量温度（图5）。测温后，如果搅拌物过热，直到储罐冒出蒸汽操作员才会发现，CSB认为至少这起事故中是这样的。Figure 5. Mixing tank mechanical systems图5 搅拌储罐的机械系统2.4 Ventilation The ventilation in the mixing area consisted of local exhaust and area ventilation systems. 2.4.1 Local Exhaust Ventilation The local exhaust system includ

26、ed two exhaust fans connected to a main duct with flexible ducts extending into the tops of the mixing tanks (Figure 5). This system was incapable of controlling vapors released from the tank because both exhaust fan drive belts were broken before the incident, and it was not designed to capture and

27、 remove a high volume of vapors from an open top tank. 2.4通风搅拌区域的通风系统由局部排风和区域通风系统构成。2.4.1局部排风系统局部排气系统包括两个排气风扇，风扇与延伸到搅拌罐顶部的主管道相连。该系统不能控制储罐的蒸气泄漏，因为： 事发前两个排风扇传动带都已断掉； 设计时并未考虑到在敞口储罐上方采集和移除大量蒸汽。2.4.2 Area Ventilation The area ventilation system included one supply and two exhaust fans mounted at ceiling

28、level. There were no floor level exhaust registers (floor sweeps) to remove heavy vapors that accumulated on the floor. Because the exhaust registers were located at ceiling level, and were a significant distance from the top of the tank, the system was incapable of removing tank vapors. Thus, when

29、the mixture boiled, the vapor overflowed the tank and spread along the floor throughout the chemical mixing and surrounding areas. 2.4.2区域通风区域通风系统包括安装在天花板上的一个送风扇和两个排风扇。没有地面排气装置（吸尘装置），以去除积聚在地板上的高浓度蒸气。由于排风扇安装在距离储罐顶部很远距离的天花板上，因此该系统无法清除储罐蒸汽。因此，当搅拌物沸腾时，蒸汽逸出储罐并沿地板扩散至整个化学品搅拌区和周边区域。2.5 Eliminating Ignition

30、Sources The Hazardous (Classified) Locations (29 CFR 1910.307) standard covers the requirements for electric equipment and wiring safety in locations where flammables and combustibles are used. The mixing room was designed to meet the requirements of 1910.307, but the adjacent area where the vapor c

31、loud migrated and likely ignited, was not. If the design for this process had included the proper safety controls (i.e., local exhaust ventilation, a high temperature alarm, and/or a backup steam shutoff), the vapors would not have overflowed the tank and migrated into the adjacent areas where multi

32、ple ignition sources existed.2.5消除点火源标准“危险（分类）地点”涵盖了易燃和可燃物质使用地点的电气设备和布线安全的要求。搅拌室的设计满足上述标准的要求，但有蒸汽扩散和被点燃危险的相邻区域却不满足标准要求。如果该工艺的设计包括适当的安全控制措施（比如局部通风系统、高压警报器、备用蒸汽切断装置），那么蒸汽就不会逸出储罐并迁移到存在多处点火源的相邻区域。3. Incident Analysis 3.1 Failure Scenario The CSB investigators identified the following most likely failure scenario. On the morning of the incident, the operator began heating the batch of Super Clean and Tilt in the mixing tank. The temperature c