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The investigation of grain elevator explosions to de- termine all facts relating to an explosion can be a compli- cated task. Most explosions actually consist of a number of explosions--a primary explosion followed by one or more secondary explosions, depending on the distribution of dust throughout the elevator. Tracing the sequence of explosions is a difficult task. Factors and events leading to an explo- sion are often hidden or are not readily apparent. For example, it is common (unsafe) practice to "jog the leg" when an elevator belt is stuck. This is an attempt to free the belt by alternately stopping and starting the driving motor. Explosions have resulted from this practice when the belt parted and dropped down the leg. The question then arises as to whether the employee had been made aware of the hazard associated with this action. Facts such as these need to be known before recommendations can be made for remedial action. TECHNICAL INVESTIGATIONS - PROCEDURES, REQUIREMENTS, and RESULTS In order to discover all facts related to an explosion it is necessary to send a team of qualified observers to the site to make careful observations, record data, and interview witnesses. The team should analyze the information obtained, draw conclusions, and make recommendations for the prevention of similar occurrences in the future. The first phase of the investigation—on—site obser- vations, data collection, and interviewing witnesses—may continue for weeks or months. Primary emphasis is on seeking every conceivable clue to the initial and subsequent events. As will be noted later in this report, it is critical to avoid the adversary posture when interviewing witnesses for the obvious reason that willingness to expose every possible clue—especially by those most knowledgeable, i.e., those involved in the accident itself—will be restrained by pos- sible or imagined punitive action. The second phase should be the analyses of personal injuries, grain-handling hardware, elevator operations, combustion products, ignition sources, explosion debris, testimony of witnesses, and other evidence gathered in the first phase. In some cases physical analyses must be done in a controlled environment such as a laboratory.
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The third phase of the investigation should extract the largest number of indisputable and unambiguous conclusions possible from the analysis of the physical evidence and witnesses' statements. The objective of the total process is a recommended course of action that will reduce the frequency and severity of similar accidents. The team conducting the investigation should be composed of trained professionals whose training consists of formal education, professional specialization, and on-site ex- perience. The team's competences should include the follow- ing specialities: Phenomena of dust explosions Mechanics of blast damage Mechanics of grain elevator operation Interviewing of witnesses Electrical engineering Safety regulations and codes Systems analysis At least one and preferably all team members should be cap- able photographers. One of the primary requirements for the investigative team is its availability to respond to a call and go immedi- ately to the site of an explosion. Evidence of causative factors in an explosion disappears rapidly after the inci- dent. Therefore, it is critical that the investigators arrive at the scene as soon as possible. They should be able to depart for the explosion site within two hours of notification. Return visits during salvage or demolition operations may be necessary. Although OSHA, presently, has the responsibility for the investigation of grain elevator explosions, it has no author- ity to isolate the scene or restrict the activities of others having an interest in the explosion. As mentioned before, it has no designated authority or responsibility for deter~ mining a complete reconstruction of the event. In current practice numerous federal, state, and local officials, industry representatives, insurance investigators, etc., can and do appear on the scene of an explosion to extract only that evidence pertinent to their own special interests. Their findings rarely reach the public except through the news media.
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8 The authority needed by an investigating group consists of four parts: 1. Authority at the accident scene to physically isolate the scene, collect evidence, interview witnesses, conduct salvage and demolition (great destroyers of evidence), and communicate with the news media; 2. Authority for subsequent analyses, simulation, and testing following the assembly of on-site evidence to resolve causative factors; 3. Authority to conduct public hearings for additional fact-finding as necessary; and 4. Authority to publish all findings related to the explosion in a public report made available to any interested party. Any permanent federal agency that is given the authority to investigate grain elevator explosions for cause must be completely autonomous, as is the National Transportation Safety Board. Rule-making agencies that can take punitive action are primarily interested in discovering violations of codes and regulations. They are likely to seek out causes and details of an explosion only if they have some bearing on a violation. Since their mandate is to enforce rules, this immediately places them in an adversary position in the eyes of the people at the site of the explosion. Even if a rule-making agency re-directs the emphasis of its investiga- tions along the lines recommended by this panel, this will not eliminate the adversary impression. Thus, even with the best of intentions, such a group would always work under a handicap that usually would be severe enough to obstruct its investigation. The panel feels that, in order to obtain a thorough knowledge of the causes and prevention of grain elevator explosions, it is critical that investigations be conducted as much as possible in a non-adversary environment. The use of adversary procedures is likely to lead to serious errors in explosion investigations. The ideal way to elimin- ate the adversary relation would be to grant immunity from prosecution to individuals who testify on the explosion. This ideal may not be possible because the authority to grant immunity is generally quite limited. Further, there are occasions involving malicious behavior for which society demands punishment.