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From page 29... ... 29 This chapter examines the completeness and quality of 6 of the 15 tasks in the Pipeline and Hazardous Materials Safety Administration–Federal Railroad Administration (PHMSA–FRA) Task Force initiative that have specific relevance to the transportation of liquefied natural gas (LNG) Read the entire page →
From page 30... ... 30 PREPARING FOR LNG BY RAIL TANK CAR system is used mainly for the movement of freight in much larger and heavier cars and on longer trains. The Task Force reviewed the experience in Japan in the most depth, finding that 8 to 10 railcars carry LNG per day. Read the entire page →
From page 31... ... TASKS SPECIFICALLY RELEVANT TO TRANSPORTING LNG BY RAIL 31 FULL-SCALE IMPACT TESTING The Task Force's Full-Scale Impact Testing of a DOT-113 tank car is part of an ongoing FRA testing program intended to develop standardized testing and simulation methodologies for quantifying the puncture resistance of tank cars. The testing program originated in 2007 when The Dow Chemical Company, Union Pacific Railroad, and Union Tank Car Company collaborated with FRA and the Volpe National Transportation Systems Center on the Next Generation Rail Tank Car Project4 for testing designed to be repeatable and reproducible.5 Impact testing establishes the baseline puncture resistance of a given tank car design reported in relation to speed and impactor size. Read the entire page →
From page 32... ... 32 PREPARING FOR LNG BY RAIL TANK CAR program, however, is expected to resume in late 2021 with two additional tests with tanks holding a cryogenic liquid. The first test will use another surrogate tank car filled with liquid nitrogen. Read the entire page →
From page 33... ... TASKS SPECIFICALLY RELEVANT TO TRANSPORTING LNG BY RAIL 33 punctured given different tank car design specifications. Simulations were run for multiple scenarios where: • The derailment initiates at 30, 40, and 50 mph with the leading truck of the first car; • Terrain varies; • Loads experienced by the tank vary; • Objects impacting the tank vary (i.e., such as a coupler head or broken rail) Read the entire page →
From page 34... ... 34 PREPARING FOR LNG BY RAIL TANK CAR sustaining 5 punctures.12 At 50 mph, the DOT-113C120W9 tank cars would sustain 6 punctures, compared with 7.3 for the standard DOT-113 tank cars.13 It merits noting the model predicted that some of the tank cars could sustain multiple punctures so that the number of punctured tank cars could be lower than the total number of punctures.14 The simulation results relate to other tasks regarding tank car design and derailment dynamics. As discussed below, the Worst-Case Scenarios Model task uses the predicted number of punctures and derailed tank cars as input for assessing the likely consequences of an accident. Read the entire page →
From page 35... ... TASKS SPECIFICALLY RELEVANT TO TRANSPORTING LNG BY RAIL 35 Without knowing these conditions, some of the results presented from the simulation would be difficult to verify or reproduce. Reducing the uncertainty about these parameter choices would build confidence in the model's applicability. Read the entire page →
From page 36... ... 36 PREPARING FOR LNG BY RAIL TANK CAR the tank is affected by experimental design features such as wind, shielding from the flatcar, and burner size.16 The report from this testing identified additional data analysis needed to support the second phase of testing, including measurements of internal tank conditions, degradation of the insulation material, the heat flux applied to the tank, and the flow out of the PRVs as a function of time and internal pressure. The plan for the second phase of testing is to fill the portable tank with LNG and place it on a flatcar exposed to an LPG pool fire. Read the entire page →
From page 37... ... TASKS SPECIFICALLY RELEVANT TO TRANSPORTING LNG BY RAIL 37 the same, details about similarities and differences in the PRV systems of the portable tank and DOT-113 tank car are needed for this purpose. Recognizing that Phase 2 has not commenced, the committee believes that there is time to make changes to the planned testing that could improve the quality of the data collected and their analysis. Read the entire page →
From page 38... ... 38 PREPARING FOR LNG BY RAIL TANK CAR • Performing the fire test for 100 minutes and a torch fire for 30 minutes in conformance with regulation to provide consistency in evaluating fire performance according to tank car specifications;26 • Evaluating an LNG fireball and tank fragmentation in the event of a BLEVE to prepare emergency response personnel for combustion and non-combustion hazards; • Assessing the potential for cryogenic damage cascading to adjacent tanks by evaluating topography surrounding the rail tracks that could support pool formation because a cryogenically damaged tank impacted by a pool fire can potentially alter PRV performance;27,28 and • Performing a non-destructive thermal test of an LNG-laden DOT113C120W9 tank car using radiant heat panels to gather data on the internal thermal response of the tank that could be used to assess model performance with regard to predicting heat transfer and multi-phase behavior. WORST-CASE SCENARIOS MODEL The Worst-Case Scenarios Model task posited four hazard scenarios involving a release of LNG simultaneously from five tank cars damaged from a unit train derailment accident. Read the entire page →
From page 39... ... TASKS SPECIFICALLY RELEVANT TO TRANSPORTING LNG BY RAIL 39 factors such as population density and the areas affected by the hazards. The model assumes that a unit train consisting of standard DOT-113 tank cars (with an outer shell thickness of 7/16 inches) Read the entire page →
From page 40... ... 40 PREPARING FOR LNG BY RAIL TANK CAR requirements for cryogenic materials, redundant pressure relief systems (valves and safety vents) , and insulation systems (an insulating wrap and annular vacuum space to prevent external heat reaching the inner tank) Read the entire page →
From page 41... ... TASKS SPECIFICALLY RELEVANT TO TRANSPORTING LNG BY RAIL 41 fire testing and full-scale impact testing of the DOT-113C120W9 tank car. Furthermore, for completeness of the task, the Task Force should make the following enhancements: • Evaluating the heat flux from a jet fire from a punctured tank and impinging on an adjacent tank to assess the potential for cascading damage from this combustion event because it was missing from the hazards initially listed in the model; • Evaluating the potential for valve damage and ruptured lines that could contribute to a release, which was not included in the initial model; • Evaluating the total amount of LNG that potentially could be released from cascading damage to adjacent tank cars from partial submersion in an unignited pool of LNG and/or partial exposure to the heat flux from a pool fire; • Evaluating the potential hazard to emergency responders of a rapid phase transition from an LNG spill onto a body of water, considering that track infrastructure commonly runs along rivers; • Evaluating explosion hazards from an unignited spill of LNG resulting in vapor dispersion in an environment with confined or congested spaces because the model only represents the scenario occurring in an open area without any factors that could affect the spread of the pool or vapor cloud; • Discussing fire propagation in a high-density environment and the potential resulting semi-confined, confined, or congested hazard areas because the model does not account for the population exposed; • Using the thermal radiant heat flux range of 475–540 kW/m2 instead of the 250 kW/m2 currently used in the model for an LNG fireball when determining the hazard area because the higher value is LNG-specific and greater than what is reported for an LPG fireball;34 and • Using an approved code (i.e., LNGFIRE3) Read the entire page →
From page 42... ... 42 PREPARING FOR LNG BY RAIL TANK CAR heat flux emitted by pool fire and fireball were not) Read the entire page →
From page 43... ... TASKS SPECIFICALLY RELEVANT TO TRANSPORTING LNG BY RAIL 43 The Volpe Center determined that the methodology in the QRA for the special permit was reasonable and achieved several of its stated goals. The review also concluded, however, that the analysis was limited in several areas, including a comparison with the risks involved in other modes long-permitted to transport LNG (i.e., marine tankers and trucks) Read the entire page →
From page 44... ... 44 PREPARING FOR LNG BY RAIL TANK CAR the results of other Task Force evaluations, such as the tasks for puncture and derailment analyses, tank car performance in accidents, worst-case scenario modeling, loading and unloading operations, route analyses, and security evaluations. Moreover, a QRA can serve as a means of continuous improvement by integrating information as new results from the Task Force's program and other safety assurance activities progress. Read the entire page →

From page 29...

... 29 This chapter examines the completeness and quality of 6 of the 15 tasks in the Pipeline and Hazardous Materials Safety Administration–Federal Railroad Administration (PHMSA–FRA) Task Force initiative that have specific relevance to the transportation of liquefied natural gas (LNG)