Identification of bulk package design performance measures is the main goal of an accident damage database. To achieve this goal, those tank parts and appurtenances that may influence bulk package performance should be included. Another consideration when determining variables to include in an accident damage database is how manageable such a database will be. Therefore, in addition to evaluating the commercially available tank parts, all stakeholders were asked to:
Survey respondents were asked to indicate their interest in having the following items evaluated:
Other parts of the tank that are usually damaged and involved in the release of lading should also be considered for inclusion in an accident damage database. To determine which parts of the tank are usually damaged, the stakeholders were asked to consider three types of accidents that may or may not result in lading loss: the first type of accident consists of incidents in which the bulk package experiences a rollover; the second type consists of incidents in which there are one or more additional vehicles involved in the crash; and the third type consists of incidents in which the vehicle transporting hazardous materials is the only vehicle involved and it does not rollover. Manufacturers Of the suggested above items to be evaluated in a possible database, the bulk package manufacturers who responded to the survey are most interested in evaluations of roll stability devices and accident prevention devices. Evaluations of accident protection devices, valve design and location, tank shape, tank wall thickness and material strength/toughness, and baffle and bulkhead locations would also be useful. In addition, the bulk package manufacturers identified several components as the most likely to be damaged or result in loss of lading. In an incident in which the cargo tank experiences a rollover, damaged components include top fittings, particularly vents and pipe nozzles (if the degree of rollover is approximately 180o) or the tank side (if the degree of rollover is approximately 90o); however, there was some agreement that the components most susceptible to lading loss were small diameter fittings far from the accident damage, “small” fittings on the vessel top centerline, and vent nozzles. In incidents in which one or more additional vehicles are involved in a crash, the parts of the tank most likely to be damaged may include the bottom piping system; however, the towing tractor or rear bumper protects the package in most of these situations. In these types of incidents, the components that would be most susceptible to lading loss are believed to be the outlet piping of a rear-unload cargo tank and the product retention bottom piping system. Finally, in an incident in which the vehicle transporting hazardous materials is the only vehicle involved in the accident and it does not rollover, the parts of the tank that are mostly likely to be damaged may include the vessel wall. One manufacturer indicated that, in general, this type of incident would not result in much, if any, damage and little, or no, release of product. Repair Facilities Repair facility respondents indicated that existing venting requirements should be evaluated by the proposed possible accident damage database. Additionally, type and thickness of accident damage material and stressed areas and bulges / indentations between baffles of the tank should be included. Several components were identified by the repair facility survey respondents as the most likely to be damaged or result in loss of lading. For all three crash scenarios the following components were identified as most likely to be damaged:
Additionally, the following set of tank components were identified as most likely to be damaged in an incident in which either the cargo tank experiences a rollover or there are one or more additional vehicles involved in a crash:
Tank jacket is the only component identified as most likely to be damaged in an incident in which either the cargo tank experiences a rollover or the vehicle transporting hazardous materials is the only vehicle involved and does not rollover. Furthermore, the tires and wheels were the only tank components identified as most likely to be damaged in incidents, involving one or more vehicles, in which the tank does not rollover. Tank components that were unique to an incident in which the cargo tank experiences a rollover include spill dams, overturn rails, upper coupler assembly, lids and baffles. Tank components that were unique to an incident in which there was one or more additional vehicles involved in the crash include internal valves, side cabinets, drain lines, lights, and wiring. In general, for all three scenarios, the components identified as most likely to be involved in the release of lading if the part is damaged is the tank shell (for non-MC 331 tanks) and valves. Additionally, for incidents not involving a rollover, piping was identified as most likely to be involved in the release of lading. Carriers The majority of carrier respondents indicated that they were either interested or very interested in all of the items suggested above with the exception of wet lines. Lowered center of gravity and corrosion resistance were also identified as performance measures to evaluate. For all three crash scenarios (rollover, multiple-vehicle, and single-vehicle crashes) several components were identified as most likely to be damaged, although the damage locations tend to differ. For rollover scenarios, damage may occur anywhere on the tank. Multiple vehicle crash scenarios tend to result in damage to the lower half of the tank. The most common single vehicle crash identified by the respondents was an incident in which the trailer jack-knifed. In such a scenario the damage is confined to the front 25% of the trailer. The following components are most likely to be damaged during all three crash scenarios:
Additionally, according to the carriers who responded to the survey, in an incident in which the bulk tank experiences a rollover, the following tank parts are also most likely to be damaged:
Shippers The majority of shipper survey respondents indicated that they were either “interested” or “very interested” in the evaluation of roll stability devices, accident prevention devices, accident protection devices, valve design and location, and tank size. Shipper opinions ranged between “Not Interested” and “Very Interested” when considering the evaluation of tank shape, tank wall thickness and material strength / toughness and tanks with a lowered center of gravity. In comparison, shippers were less interested in the evaluation of baffle and bulkhead location and wet lines. The shippers who responded to the survey indicated that the front head, fittings (top, bottom and rear), shell, valve protection box, lights, ladder, hose rack, fifth wheel, dolly legs, wheels, rims, and tires are most likely to be damaged in an incident in which the bulk tank experiences a rollover. In such a scenario, the same shippers indicated that safety relief valves, rupture discs, pressure building coils (evaporator coils), and fittings (including wash out caps) are most likely to be involved in the release of lading if the part is damaged. In an incident in which there was one or more additional vehicles involved in the crash, bursting discs, trailer chassis, back outlet valves (if present) and piping below the tank are believed to be the most vulnerable to damage. Furthermore, in such a scenario, damage to piping, valves, shell and evaporator coils would most likely lead to a loss of lading. Finally the rear bumper, trailer shell, fittings (bottom, rear or top fittings depending on the scenario), relief valves, and hydraulic pumping equipment between the trailer and cab are believed to be most likely to sustain damaged in an incident in which the vehicle transporting hazardous materials is the only vehicle involved and does not rollover. In such a scenario, damage to the jacket of a cryogenic cargo tank, trailer piping, and valves would most likely lead to a loss of lading. Researchers In general researcher’s opinions on which package design information is useful to their research differed greatly from researcher to researcher. Those who were interested in bulk tank performance and conditional probability of release indicated that the most useful package design information is type(s) of accident protection devices followed by type(s) of roll stability devices, tank shape, tank wall thickness, and baffle and bulkhead location. Presence of wet lines, type of wet line construction and valve design and location were data fields judged to be not as useful to researchers focusing on bulk package performance. Additional package design information to consider included the presence and type of top fittings protection, package capacity, type of mounts and design center of gravity height. For other researchers, including those who study risk associated with routing and evaluate hazardous material risks for other modes, package design information is less useful. Researchers responding to the survey believe that in an incident in which the cargo tank experiences a rollover, damage to the tank shell, top fittings and valves can be expected. One researcher said that damage to the head occurs rarely. In this type of incident, damage to the tank body is believed to be the most likely source of a hazardous material release. In an incident in which there are one or more additional vehicles involved in a crash, piping and the tank shell are thought to be most likely to be damaged and result in a hazardous materials spill. Finally, in an incident in which the vehicle is the only vehicle involved and it does not rollover, damage to piping and bottom fittings as well as the frame and undercarriage is expected. In such a scenario, the piping and bottom fittings are thought to be the most likely to be involved in a release of hazardous materials. |
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F) Tank Parts and Appurtenances to Include in the Proposed Database |