{"operation":"document","citation":"ERG 2024, BLEVE and Heat-Induced Tear","title":"BLEVE and Heat-Induced Tear","source_type":"guidance","agency":"U.S. DOT / Transport Canada / SICT","status":"guidance","official":true,"published_on":"2024-04-04","effective_on":null,"summary":"Official ERG2024 bleve and heat-induced tear guidance, pages 359-361.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-erg-2024-bleve.json","markdown":"https://regulus.evalyn.ai/document/phmsa-erg-2024-bleve.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-erg-2024-bleve","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2024-04/ERG2024-Eng-Web-a.pdf#page=359","body":"BLEVE AND HEAT INDUCED TEAR\nBLEVE (BOILING LIQUID EXPANDING VAPOR EXPLOSION)\nThe following section presents important safety-related information on BLEVEs, including a\ntable, to consider in a situation involving Liquefied Petroleum Gases (LPG), UN1075.\nLPGs include the following flammable gases:\n•\nUN1011 - Butane •\nUN1077 - Propylene\n•\nUN1012 - Butylene •\nUN1969 - Isobutane\n•\nUN1055 - Isobutylene •\nUN1978 - Propane\nA BLEVE occurs when a fire impinged or damaged tank car fails to contain its internal pressure\nand explodes with a sudden product release. This catastrophic failure is more likely to occur\nwith damaged pressure tank cars, even in the absence of an active fire.\nThe main hazards from a LPG BLEVE are:\n•\nFire: If the released substance is ignited, there is an immediate fireball.\n•\nThermal radiation: At a distance of about 4 times the radius of a fireball, the heat\nradiated from a fireball is enough to burn exposed skin in 2 seconds. Wearing protective\nclothing limits the thermal radiation dose.\n•\nBlast: A concussive force caused by the sudden release of the pressurized substance.\nFor a BLEVE occurring out in the open, the blast strength at a distance of 4 times the\nradius of a fireball can break window glass and may cause minor damage to buildings.\n•\nProjectiles: Tank failure can throw metal fragments over large distances. These\nfragments can and have been deadly.\nThe danger decreases as you move away from the BLEVE centre. The furthest-reaching\nhazard is projectiles.\nFor a video with information on critical safety issues concerning BLEVEs, please visit\nhttps://www.tc.gc.ca/eng/tdg/publications-menu-1238.html.\nHEAT INDUCED TEAR (HIT)\nA heat induced tear (HIT) is a rupture of a NON-PRESSURE tank car containing flammable\nliquids when exposed to the intense heat of a fire. The metal will soften and the pressure in\nthe tank car will increase which can lead to containment failure. The tear generally occurs\nat the vapor space (upper side) of the container, venting large quantities of flammable liquid\nand vapors at high speed. A fireball and an intense heat wave will occur.\nCompared to BLEVEs, HITs rarely result in the projection of tank car fragments. Heat induced\ntearing has occurred within 20 minutes of the derailment and as long as 10+ hours following\nthe initial fire.\nResponding to these types of incidents (BLEVE and HIT) requires specialized training,\nequipment and a tactical approach.\nPage 357\n\nBLEVE – SAFETY PRECAUTIONS\nUse with caution. The following table gives a summary of tank properties, critical times,\ncritical distances and cooling water flow rates for various tank sizes. This table is provided\nto give responders some guidance but it should be used with caution.\nTank dimensions are approximate and can vary depending on the tank design and\napplication.\nMinimum time to failure is based on severe torch fire impingement on the vapor space\nof a tank in good condition, and is approximate. Tanks may fail earlier if they are damaged\nor corroded. Tanks may fail minutes or hours later than these minimum times depending\non the conditions. It has been assumed here that the tanks are not equipped with thermal\nbarriers or water spray cooling.\nMinimum time to empty is based on an engulfing fire with a properly sized pressure relief\nvalve. If the tank is only partially engulfed, then time to empty will increase (i.e., if tank is 50%\nengulfed, then the tanks will take twice as long to empty). Once again, it has been assumed\nthat the tank is not equipped with a thermal barrier or water spray.\nTanks equipped with thermal barriers or water spray cooling significantly increase the\ntimes to failure and the times to empty. A thermal barrier can reduce the heat input to a\ntank by a factor of ten or more. This means it could take ten times as long to empty the tank\nthrough the Pressure Relief Valve (PRV).\nFireball radius and emergency response distance is based on mathematical equations\nand is approximate. They assume spherical fireballs and this is not always the case.\nTwo safety distances for public evacuation. The minimum distance is based on tanks\nthat are launched with a small elevation angle (i.e., a few degrees above horizontal). This is\nmost common for horizontal cylinders. The preferred evacuation distance has more margin\nof safety since it assumes the tanks are launched at a 45 degree angle to the horizontal.\nThis might be more appropriate if a vertical cylinder is involved.\nIt is understood that these distances are very large and may not be practical in a highly\npopulated area. However, it should be understood that the risks increase rapidly the closer\nyou are to a BLEVE. Keep in mind that the furthest reaching projectiles tend to come off in\nthe zones 45 degrees on each side of the tank ends.\nWater flow rate is based on 5 ( √capacity (USgal) ) = USgal/min needed to cool tank\nmetal.\nWarning: the data given are approximate and should only be used with extreme caution.\nFor example, where times are given for tank failure or tank emptying through the pressure\nrelief valve – these times are typical but they can vary from situation to situation. Therefore,\nnever risk life based on these times.\nPage 358\n\nWARNING:\nThe data given are approximate and should only be used with extreme caution. These times can vary from situation to situation.\nLPG tanks have been known to BLEVE within minutes. Therefore, never risk life based on these times.\nCapacity Diameter Length Propane\nMass\nBLEVE\n(USE WITH CAUTION)\nMinimum time\nto failure for\nsevere\ntorch\nLitres (Gallons) Meters (Feet) Meters (Feet) Kilograms (Pounds) Minutes Approximate\ntime to empty\nfor engulfing\nfire\nMinutes Fireball\nradius\nEmergency\nresponse\ndistance\nMinimum\nevacuation\ndistance\nPreferred\nevacuation\ndistance\nCooling water\nflow rate\nMeters (Feet) Meters (Feet) Meters (Feet) Meters (Feet) Litres/min USgal/min\n100 (26.4) 0.3 (1) 1.5 (4.9) 40 (88) 4 8 10 (33) 90 (295) 154 (505) 307 (1007) 97 26\n400 (106) 0.61 (2) 1.5 (4.9) 160 (353) 4 12 16 (52) 90 (295) 244 (801) 488 (1601) 195 52\n2000 (528) 0.96 (3.1) 3 (9.8) 800 (1764) 5 18 28 (92) 111 (364) 417 (1368) 834 (2736) 435 115\n4000 (1057) 1 (3.3) 4.9 (16.1) 1600 (3527) 5 20 35 (115) 140 (459) 525 (1722) 1050 (3445) 615 163\n8000 (2113) 1.25 (4.1) 6.5 (21.3) 3200 (7055) 6 22 44 (144) 176 (577) 661 (2169) 1323 (4341) 870 230\n22000 (5812) 2.1 (6.9) 6.7 (22) 8800 (19401) 7 28 62 (203) 247 (810) 926 (3038) 1852 (6076) 1443 381\n42000 (11095) 2.1 (6.9) 11.8 (38.7) 16800 (37038) 7 32 77 (253) 306 (1004) 1149 (3770) 2200 (7218) 1994 527\n82000 (21662) 2.75 (9) 13.7 (45) 32800 (72312) 8 40 96 (315) 383 (1257) 1435 (4708) 2200 (7218) 2786 736\n140000 (36984) 3.3 (10.8) 17.2 (56.4) 56000 (123459) 9 45 114 (374) 457 (1499) 1715 (5627) 2200 (7218) 3640 962\nPage 359","truncated":false,"body_characters":6765}