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1、Fire Investigation Summary Grain Elevator Explosion Haysville, Kansas June 8, 1998 A series of explosions in a large grain storage facility resulted in the deaths of seven people. Dust explosions are a leading hazard in the grain industry. A lack of proper housekeeping and equipment maintenance can
2、contribute to the accumulation of combustible dust. If combustible dust is suspended and ignited the resulting explosions can result in the loss of life and property. National Fire Protection Association Fire Investigations Department 1999 NFPA Fire Investigations Report Summary Haysville, Kansas Gr
3、ain Elevator Explosion On Monday, June 8, 1998, at approximately 9:20 a.m., a series of explosions occurred at a grain elevator facility in Haysville, Kansas (five miles south of Wichita). There were seven fatalities as a result of the explosions. Ten workers were injured by the blasts. NFPA Fire In
4、vestigator Robert Duval arrived at the site on Tuesday, June 9, 1998, and joined a team of investigators from Sedgwick County; the City of Wichita, the Kansas State Fire Marshals Office, and the Bureau of Alcohol, Tobacco, and Firearms. The grain elevator was one of the largest in the world. The fac
5、ility contained 246 concrete silos, each measuring 30 feet (9.1 m) in diameter and over 120 feet (36.6 m) in height. Each silo could hold approximately 70,000 bushels (2,464 m3) of grain, making the total capacity of the facility nearly 21 million bushels (739,200 m3), including the 7 million bushel
6、s (246,400 m3) contained in the headhouse bins. At the time of the incident, the facility was filled to about 33 percent of capacity. The facility measured over 2,700 feet (823 m) or approximately one-half mile in length. Wheat was the main product being stored in this facility. The explosions occur
7、red as the facility was being prepared for the early summer harvest of wheat in the Midwest. Workers were preparing the facility for the harvest by cleaning the gallery houses at the top of the silos as well as the conveyor tunnels under the silos. Routine maintenance, which included greasing bearin
8、gs on the four conveyor lines, was also taking place throughout the facility. An unknown ignition source ignited dust within the facility and resulted in a series of explosions that killed seven workers and severely damaged the entire structure. The actual ignition source may never be known due to t
9、he damage that occurred in the central portion of the facility (in the tunnels beneath the silos and in the space under the headhouse). Information regarding the events that took place in these areas prior to the explosions will be difficult to obtain since all of the employees working in this area
10、at the time of the explosions were killed. Following the initiating event, several explosions occurred throughout the facility (statements of witnesses regarding the number of explosions ranged from two to five). The first explosion caused dust within the facility to be placed into suspension in the
11、 air thereby contributing to a series of subsequent explosions. The rescue and recovery efforts that followed the explosions involved local, state, and federal resources. The Sedgwick County Fire Department was assisted at the scene by the City of Wichita Fire Department, Oklahoma City Fire Departme
12、nt Rescue Team, personnel and equipment from both Fort Riley Army Base and McConnell Air Force Base, as well as the Federal Emergency Management Agency (FEMA) who provided a Urban Search and Rescue (US Wichita Fire Department; the Kansas State Fire Marshals Office; the Bureau of Alcohol, Tobacco, an
13、d Firearms, and the Federal Emergency Management Agency is greatly appreciated. All of these agencies provided significant support and assistance in the on-scene and subsequent report development portions of this process. ? 1999 National Fire Protection Association Grain Elevator Explosion, Haysvill
14、e, Kansas 5 Page II. BACKGROUND THE FACILITY The grain elevator was constructed in 1953. The facility was a terminal-type elevator with a capability of loading and unloading of both rail cars and over-the-road trucks. The structure consisted of a total of 246 concrete silos, each measuring 30 feet (
15、9.1 m) in diameter. Each silo was 120 feet (36.6 m) high and had a capacity of 70,000 bushels (2,464 m3) of grain. Interstitial spaces (fan bins) between silos at the ends of silo sections were also utilized for grain storage. The total capacity of the facility was approximately 21 million bushels (
16、739,200 m3). (The headhouse contained 16 bins with a total capacity of approximately 7 million bushels (246,400 m3). The total length of the facility was over 2,700 feet (823 m). Diagram of facility Fig No. 1 The reinforced concrete headhouse structure located in the center of the facility stood app
17、roximately 214 feet (65.2 m) high. The headhouse contained four bucket-type elevators (“legs”) for transporting product to the upper levels of the facility. This structure contained a single “manlift“ for the movement of personnel to the upper reaches of the structure. The headhouse structure consis
18、ted of multiple levels. The lowest level referred to as the “boot pit,“ is where grain from both the truck and rail off-loading ? 1999 National Fire Protection Association Grain Elevator Explosion, Haysville, Kansas 6 Page operations was directed. The grain was then routed into the four legs for tra
19、nsport up to the garner and scale levels. At the garner and scale levels in the upper portion of the headhouse, the grain was weighed and routed onto conveyor belts for placement into silos. Fig. No. 2 - Typical concrete grain elevator (Fig-3-26F from Fire Protection Handbook 18th Edition p 3-287) T
20、he conveyor system at this facility consisted of four independent belts (two north and two south). The fiber- reinforced rubber belts were routed through tunnels beneath the silos and through gallery houses at the top of the silos. The four tunnels measured 8 feet (2.4 m) wide and 7 feet, 3 inches (
21、2.2 m) high and were constructed with walls and ceilings of 8 inch to 16 inch (200 mm to 400 mm) thick concrete. Each tunnel was approximately 1,050 feet (320 m) in length. There were several locations within the tunnels where a worker could pass between two parallel tunnels. Access to the tunnels ?
22、 1999 National Fire Protection Association Grain Elevator Explosion, Haysville, Kansas 7 Page was provided through hatches at numerous locations throughout the facility. The tunnels contained the 42 inch (1.1 m) wide conveyor belts and associated drives and rollers. The gallery houses were construct
23、ed of corrugated metal panels on steel frames. The gallery houses measured 48 feet (14.6 m) wide and 12 feet (3.6 m) high. A single access path (25 feet (7.6 m) wide) ran between the belts in the gallery houses. The loading areas consisted of a rail siding on the west side of the facility and a truc
24、k loading area on the east side. Rail cars or trucks could unload through chutes at the bottom of the trailer or rail cars or be loaded via an overhead chute, in either facility. The rail loading area had a corrugated metal roof on steel frame and was open on four sides. The truck loading station co
25、nsisted of two bays, one of which was enclosed and one which was open-air. A storage building was located alongside the southern half of the facility on the east side. This structure consisted of a single-slope roof structure of corrugated metal panels on steel frame. The building was approximately
26、1,200 feet (365.7 m) long and 50 feet (15.2 m) high at its highest point. This building was used to store maintenance equipment and supplies. Eight warehouse structures were located on the east side of the northern portion of the structure. These buildings were formerly used for grain storage. Tenan
27、ts, including a public warehouse and a metal materials dealer, occupied the buildings. The warehouse buildings were 120 feet (36.6 m) wide and ranged from 500 feet to 750 feet (152 m to 229 m) in length and were approximately 50 feet (15.2 m) high at the peak. The facility office was located approxi
28、mately 100 feet (30.5 m) east of the headhouse. This single-story building was constructed of concrete block walls with a wood-frame roof structure. This building measured approximately 100 feet by 30 feet (30.5 m by 9.1 m). Dust collection in the facility was completed through a series of units loc
29、ated throughout the complex. The main collection units were located outside at the loading/unloading points of the complex. These units consisted of two cyclone-type collectors at ground level and a bag-type collector located on top of the truck trailer loading station. A collection bin, 20 feet (6.
30、1 m) in diameter and 50 feet (15.2 m) high, was located adjacent to the bag collector near the truck station. These units provided collection for the lower levels of the loading stations (rail and truck) as well as the lower portion of the headhouse. Numerous other ventilation fans and blowers were
31、located on the east and west sides of the silos. A dust collector was located on the roof of the headhouse. (This unit was reported to be out of service at the time of the explosions.) Details on the dust collection equipment are minimal due to the location of some of the units and the damage incurr
32、ed by the units. FIRE DEPARTMENT The Sedgwick County Fire Department (SCFD) is a full-time department with 139 members. The department staffs eight stations with 40 members assigned to each shift. ? 1999 National Fire Protection Association Grain Elevator Explosion, Haysville, Kansas 8 Page The depa
33、rtment has seven engines and two aerial units and two special units. Emergency medical coverage is provided by the Sedgwick County Department of Emergency Medical Services, which staffs ten ambulances with 140 personnel. Sedgwick County encompasses 640 square miles (1657.6-sq km) around the area of
34、the City of Wichita. The SCFD responded to 5436 calls in 1997. GRAIN STORAGE AND HANDLING Raw Materials Grains consist of many components that are combustible under certain conditions. The components include starch, fibers, and oils. As whole grain kernels are broken during handling and processing,
35、the probability of a fire or explosion increases as the starch and other particles are released. As the particle or kernels size decreases, the potential for fire or explosions increases. The reduction of the kernel size occurs through the handling of the products as well as milling and other proces
36、sing steps.1 Storage Grain in bulk commodities is stored in numerous types of facilities and configurations. The most common configurations are upright structures such as concrete silos and steel tanks. These installations utilize gravity for loading and unloading of product. The size of these stora
37、ge units can range from 1,000 bushels (35.2 m3) to upwards of 2 million bushels (70,400 m3). Belt Conveyors The main function of grain elevators, other than the storage of the product, is the moving of product both vertically and horizontally through a series of conveyors and other methods.2 The tro
38、ugh-belt conveyor is the most common method of product transfer in the grain industry. Based on the capacity of the operation, different belt widths and drive speeds are available with this method. The Haysville facility was equipped with four continuous trough-belt type conveyors (Conveyors Nos. 1
39、- 4). Belt conveyors are reliable and pose limited maintenance requirements. However, the belts and associated drives are susceptible to mechanical failure when poorly maintained. The hazards associated with this type of product transfer are the fire hazard posed by the combustible rubber belting, a
40、nd the amount of dust generated at distribution points.3 1 Fire Protection Handbook, 18th Edition (NFPA, 1997) pp. .3-2843-285 2 Fire Protection Handbook, 18th Edition (NFPA, 1997) p. 3-286 3 Fire Protection Handbook, 18th Edition (NFPA, 1997) pp. 3-2863-287 ? 1999 National Fire Protection Associati
41、on Grain Elevator Explosion, Haysville, Kansas 9 Page Bucket Elevators Grain elevators are designed to use gravity by transporting the product to a high point and allowing the grain to flow down through hoppers, garners, scales, and cleaning screens before entering chutes that direct the product int
42、o storage bins or silos. Using gravity reduces the handling of the grain, thus reducing the amount of breakage in the grain kernels. The bucket elevator is referred to as a “leg“ in the grain industry. This method is the main means by which elevation is achieved in a processing and storage facility.
43、 The Haysville facility was equipped with four-bucket elevators in the headhouse structure. 4 Receiving and Shipping The first and last distribution point in a grain processing facility is the load/off-load area. Trucks and railcars are utilized to transport products. ( Barges and ocean going vessel
44、s are utilized in port-based facilities.) The loading/off-loading areas can be enclosed or completely in the open. These areas are connected with the main storage facility by underground tunnels or overhead conveyor systems dependent on the type of vehicle or vessel being accommodated.5 Dust Control
45、 Each point in the distribution process can produce suspended dust. A complete dust control system in a grain elevator facility contains different methods of control. Proper housekeeping and maintenance of grain-handling equipment (controlling leaks in chutes and other equipment), combined with the
46、enclosure of handling equipment, the control of belt speeds as well as the use of mechanical dust collection systems, can reduce the amounts of dust released. Additives such as oil sprayed on grain products, are also utilized to reduce dust emissions during handling. At the time of the incident, add
47、itives were not used at the Haysville facility. Mechanical dust control is the primary method of dust collection. The most common type of collection is a baghouse installation. The baghouse consists of a series of fabric filters to collect particles from air forced through the filter unit. The dust
48、recovered from the “bags“ is collected and stored in a separate container or bin. Prior to the common use of baghouse collectors, cyclone-type collectors were prominent. For this particular application, cyclones are not as efficient as baghouse collectors in collecting smaller particles. Cyclone col
49、lectors are sometimes used in series with a fabric filter system to allow for the capture of larger particles, prior to the fabric collectors.6 4 Fire Protection Handbook, 18th Edition (NFPA, 1997) p. 3287 5 Fire Protection Handbook, 18th Edition (NFPA, 1997) p. 3-288 6 Fire Protection Handbook, 18th Edition (NFPA, 1997) p. 3290 ? 1999 National Fire Protection Association Grain Elevator Explosion, Haysville, Kansas 10 Page Dust collection systems can pose a fire or