FIRE TESTS on COMPOSITE LPG CYLINDERs

BY DENIS M. MURPHY AND EUGENE PIETZAK

Last year, the Nassau County Fire Service Academy (NCFSA) in Old Bethpage, New York, became aware of a new type of composite liquefied petroleum gas (LPG) cylinder being sold in our area. We acquired several sample cylinders to conduct a series of burn tests. These tests would provide a baseline of knowledge as to how these new cylinders would behave under fire conditions. The new cylinders are radically different from the steel cylinders the fire service has encountered for decades. They use a composite technology from the aerospace industry similar to that used in SCBA cylinders.

The cylinders we tested are manufactured by the Lite Cylinder Company in Franklin, Tennessee, and its manufacturing partner, Composite Scandinavia in Pitea, Sweden. Composite cylinders have been used in Europe for a decade and are now being introduced in the United States. According to the manufacturer, “The cylinders are made of fiberglass-reinforced vinylester and weigh approximately 50 percent less than a conventional steel model. The design’s hallmark feature is its translucency, which allows users to see how much fuel is inside. Designed with a two-piece casing that can be made in several colors and is stackable, the composite cylinders are also corrosion-free. Composite Scandinavia uses air instead of water for pressure testing. The composite materials will remain rust-free and low-maintenance-soap and water is [are] all that is needed to clean the outside of the cylinder.”1 The cylinders we used were considerably more expensive than their steel counterparts, but that will be less of an issue in the future as manufacturing increases and becomes more efficient.

These cylinders have received a U.S. Department of Transportation (DOT) exemption DOT-E 13105. An interesting note to the exemption is in section 2, “Purpose and Limitations,” paragraph b, which notes: “The safety analyses did not consider the hazards and risks associated with consumer use, use as a component of a transport vehicle or other device, or other uses not associated with transportation in commerce.” 2

How will these cylinders behave under fire conditions? According to an article in BPN Online Magazine, August 2004, the manufacturer stated, “Testing and use in Europe has [have] shown that composite cylinders won’t necessarily BLEVE [boiling-liquid, expanding-vapor explosion]. Manufacturers believe, and testing has shown, that when subjected to heat and/or fire, the cylinders’ permeability will increase. This will allow the gas to seep through the walls slowly instead of releasing large amounts of gas through the valve. As a fire around the cylinder intensifies, it will appear to be glowing with fire and not BLEVE. One cylinder manufacturer told BPN Online Magazine that the average temperature of most fires is not hot enough to melt the glass fibers.”(1)

TEST FIRES

The tests conducted at the academy were nonscientific in nature and intended to provide us with a rough time to failure. We attempted to simulate two scenarios commonly encountered by the fire service. These two test fires are by no means complete or exact tools because of the many variables occurring at every incident. They should not be used to attempt to predict the behavior of these cylinders in the field.

Test 1: Pool Fire. The cylinder was placed on an open metal grate approximately five inches above a pool of burning fuel oil (photos 1, 2). The following results were noted. At three minutes, the outer protective casing burned away; the relief valve fired at three minutes and 25 seconds; and venting at the neck of the cylinder occurred at four minutes (photo 3); breach of the cylinder shell at four minutes, 25 seconds (photos 4, 5); and complete burn-off at 16 minutes. There was no BLEVE, and the cylinder remained upright throughout the test.


Photos by authors.

 


 


 


 


Test 2: Flame Impingement. The cylinder was placed approximately three feet from the end of a propane torch pressure fire. The following was noted: At less than one minute, the outer protective casing burned away (photo 6); the relief valve fired at two minutes (photo 7); and venting at the neck of the cylinder occurred at three minutes (photo 8). There was no breach of the cylinder shell (photo 9), and complete burn-off occurred at 14 minutes. There was no BLEVE, and the cylinder remained upright throughout the test.


 


 


 


 

RESULTS

Test fire results and research conducted revealed the following: The composite cylinder’s potential to BLEVE is less likely than for conventional cylinders.

The cylinder wall can be breached by fire. Although there is no catastrophic destruction of the cylinder as in a BLEVE, a large plume of fire can vent out from the breach. The cylinder valve and relief valve are the same as on a steel LPG cylinder. The valve on the composite cylinder is threaded through the composite and held in place by a steel flange on the inside of the cylinder. When sufficient heat and fire are applied to the neck, the composite opens and fire vents from around this attachment point. The valve remains in place and is not blown out. The cylinders remained in place at all times until they were hit by a hose stream. Overall, the cylinder reacted as the manufacturer had predicted it would. However, there was a larger release of gas and, subsequently, a larger amount of fire than described in the BPN article. The cylinders were surprisingly stable during both tests. It will be vital to identify these cylinders as composite cylinders if they are involved in fire.

RESPONSE RECOMMENDATIONS

Firefighters must be aware that these cylinders are now being sold in the United States.

  • Follow standard LPG response guidelines.
  • Identify the cylinder’s construction visually if possible; interview people at the scene.
  • DO NOT APPROACH if the cylinder on fire is confirmed to be a composite tank. Fire can vent out from any point on the cylinder. Approach only after the cylinder is stablized. If there is minor fire involvement at the composite cylinder, extinguish the fire and disperse any vapors.
  • If a composite cylinder is involved, first apply water directly to any exposure.
  • Steel cylinders still require immediate water application to points of flame impingement.
  • Composite cylinders are lighter than their steel counterparts; use caution to avoid displacement by hose stream.
  • Exercise caution-follow safe operational procedures, wear full protective gear and SCBA, stay upwind, and use distance and shielding for protection.

Endnotes

1. Rey, Ann, “Space-Age Technology Pushes Cylinders to New Heights,” BPN Online Magazine, August 2004, http://bpnews.com/htmlfile/magzine/mag2004/aug04/080204.htm.

2. DOT-E 13105, United States Department of Transportation, http://hazmat.dot.gov/sp_app/special_permits/docs/13000/sp13105.pdf.

DENIS M. MURPHY, a 32-year veteran of the fire service, is assistant chief instructor of the Nassau County Fire Service Academy in Old Bethpage, New York.

EUGENE PIETZAK, a 32-year fire service veteran, is a Nassau County fire marshal and first deputy chief instructor at the Nassau County Fire Service Academy in Old Bethpage, New York.

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