COMPOSITE PROPANE CYLINDERS - · PDF fileCOMPOSITE PROPANE CYLINDERS ... and aircraft. •...

COMPOSITE PROPANE CYLINDERSAn Overview of Fire Safety Risks

for Emergency Responders and Fire Marshals

By: Michael S. Hildebrand, CSP and Gregory G. Noll, CSP 1

JANUARY 2007

Propane Education & Research Council1140 Connecticut Ave., NWSuite 1075Washington, DC 20036202.452.9054www.propanesafety.com

Copyright © 2007Produced By: Hildebrand and Noll Associates, Inc.Layout and Design: Kathleen Lawyer—Lightworks Design

Note: This paper was developed by Hildebrand and Noll Associates, Inc. under contract to the Propane Education & Research Council—Docket # 12052

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TABLE OF CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Overview of Composite Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Hybrid Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Propane Cylinders Made From Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Composite Cylinder Construction Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

One-Piece Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Two-Piece Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Regulations and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

U.S. Department of Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

National Liquefied Petroleum Gas Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Fire Testing of Composite Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

The Battelle Fire Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Nassau County Fire Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Fire Testing of Cabinet Heaters with Composite Cylinders . . . . . . . . . . . . . . 11

Viewpoints on Fire Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Supporting Viewpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Opposing Viewpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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INTRODUCTION

The objective of this paper is to introduceemergency responders and fire marshals to thenew types of composite cylinders that areentering the marketplace and to provide anoverview of the fire safety risks they may pres-ent in a fire emergency scenario. The paperalso summarizes the results of recent live firetesting of various types of composite cylinderscurrently being manufactured and distributedin the United States for outdoor use and exam-ines how these cylinders may be used forfuture indoor use with cabinet heaters.

Hildebrand and Noll Associates, Inc. devel-oped this paper under an agreement with thePropane Education & Research Council(PERC). 2

OVERVIEW OF COMPOSITE MATERIALS

Composite materials are not new and havebeen used for many years in the automotive,marine, and aerospace industries. More recent-ly, composites have been used to manufacturea variety of cylinders and containers for trans-portation and storage of regulated materials. 3

Composites are highly engineered materialsdesigned for very specific applications. Theyare made from two or more different materialsto form one single structure with an identifi-able interface. The properties of the new struc-ture are dependent upon the overall propertiesof the constituent materials as well as the prop-erties of the interface. Composite materialstypically form molecular bonds in which theoriginal materials retain their identity andmechanical properties. 4

Reinforced concrete serves as a good exampleof a simple composite structure. Concrete ispoured over steel rebar to make up a singlestructural component, but the concrete andsteel still retain their individual identities. Thesteel bars carry the tension loads and the con-crete carries the compression loads. 5

HYBRID COMPOSITES

Composite products are usually hybrids man-ufactured for specific purposes. They are madeby adding some complementary material suchas fiberglass or Kevlar® fiber to a basic carbonfiber/epoxy matrix. The addition of carbon/epoxy to the fiberglass structure is used to pro-vide additional stiffness. The specific materialsselected by the manufacturer are designed toobtain characteristics required by the end usersuch as greater fracture toughness and impactresistance.

Composites have many advantages over met-als. Some of the primary advantages include:

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COMPOSITE PROPANE CYLINDERS

Figure 1 Composite materials are incorporated into automo-biles, boats, and aircraft.

• Composites are stronger and stiffer thanmetals on a density basis. This characteris-tic is important when high performance ofthe material is required but weight is afactor. For example, strength being equal,composites are lighter than steel and alu-minum. 6 Some composite cylinders are30% to 40% lighter than steel. 7

• Composites are highly corrosion resistant.Most are inert even in the most corrosiveenvironments.

• Composites can be formed into complexshapes during the fabrication process andcan be made from fewer parts. This reducesmanufacturing and assembly time andcosts.

• Composites can be made so they are trans-lucent, which allows the user to view thelevel of product inside, or they can beblended with colors.

PROPANE CYLINDERS MADE FROMCOMPOSITES

Propane cylinders made from composite mate-rials are relatively new inside the UnitedStates, but they are very common and havebeen used for many years in other countries.These cylinders are currently being legallymanufactured, transported, and distributed inthe United States. 8 The most common cylin-

ders being manufactured are the 20-poundcylinder for barbeque grills and outdoorheaters, and the 33-pound cylinder for fork-lifts. 9

The propane industry has proposed codechanges that will permit composite cylindersinside buildings, especially in residentialoccupancies in combination with cabinetheaters. 10 11

The composite cylinders currently being manu-factured are a polymer wrapped in fiberglass.An outer casing protects the cylinder. Con-struction materials include poly-acrylonitrilebutadiene styrene (ABS), high-density polyeth-ylene (HDPE), and polyethyleneterephthalate(PET).

COMPOSITE CYLINDER CONSTRUCTION FEATURES

Composite cylinders are constructed in accor-dance with U.S. Department of Transportation(DOT) special permits. The special permits arebased upon the DOT Standard FRP-1, theEuropean Standard EN 12245, and the ISO11119-3 standard. 12 Cylinders under DOT spe-cial permits can be found in two basic designs

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Figure 2 Composite materials can be made translucent sointernal liquid levels can be safely viewed.

liquid line

side view

Figure 3 The most common composite cylinders are the 20 lb.BBQ and 33 lb. Fork Lift types.

approved by the DOT. 13 These include one-piece and two-piece construction. Both typesof cylinders include the same type of approvedvalves, pressure relief devices, and overfillprevention device as found on metal propanecylinders. 14

ONE-PIECE CONSTRUCTION

The one-piece composite cylinder is currentlymanufactured by two different companies:Ragasco and Kompozit-Praha. Both compa-nies manufacturer a one-piece compositecylinder with a blow molded PET liner andHDPE jacket. 15 16 The Ragasco cylinder has aDOT special permit for use in the UnitedStates, and the Kompozit-Praha cylinder iscurrently in the special permit process.

For the one-piece fully wrapped fiberglass andresin composite cylinder, the blow-moldedhigh density polyethylene (HDPE) liner pro-vides the inner gas barrier. The compositelayer is made from a tough polymeric materialthat is chemical resistant. It is applied in a fila-ment winding process. An advanced curingprocess ensures the translucent see-throughfeature. The cylinder has a permanently at-tached outer casing made with injection-mold-ed HDPE. The outer casing provides protec-

tion for the pressure vessel as well as for thevalve. It has ergonomic handles for easy liftingand stacking. 17

TWO-PIECE CONSTRUCTION

The two-piece composite cylinder is currentlymanufactured by The Lite Cylinder Companyas a linerless two piece (top and bottom fittedtogether) with an ABS jacket. 18 The two halvesof each cylinder are wound with fiberglassaround a mandrel and then injected with plas-tic resin under high pressure in a hermeticprocess. After hardening, the two halves aretaken out of themolds and areadhesively joinedtogether. Holes aredrilled in one halffor the valve andthe two halves arebonded together tocreate the complet-ed cylinder. A ther-moplastic outer cas-ing is attached tothe cylinder to pro-vide additional pro-tection. 19

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Figure 4 One-piece construction composite cylinders.

KOMPOZIT-PRAHARAGASCO

Figure 5 One-piece construction composite cylinders.

Figure 6 Two-piece construc-tion composite cylinders.

Composiite Layer

TH

E L

ITE

CY

LIN

DE

R C

OM

AP

NA

Y

Outer Casing

Liner

REGULATIONS AND STANDARDS

In 2002 the propane industry began an effort todevelop an interest in new products thatwould potentially expand the use of propaneby U.S. consumers through the use of indoorcabinet heaters using the features of compositecylinders. 20 The problem the propane indus-try faced was that the Department of Transpor-tation regulations did not specifically covercomposite cylinders for transportation ofpropane and the National LP Gas Code pro-hibited the use of both composite cylindersand cabinet heaters indoors. 21 As a result theU.S. propane industry, under the leadership ofthe Propane Education & Research Council(PERC), funded the following projects:

1. Program to develop a template for the DOTexemption process. The template was de-veloped through an industry-wide workinggroup of over 40 members. The intent wasto establish a guide for assisting potentialcylinder manufacturers through the exemp-tion process. 22

2. Research program to assist the NationalPropane Gas Association (NPGA) in thedevelopment of a proposal to the NationalFire Protection Association 58 TechnicalCommittee for the accepted indoor use ofcomposite propane cylinders. 23 PERC en-gaged Battelle, Columbus, Ohio to conductthe research. The project was divided intotwo phases. 24

Phase 1—Investigated the market viabilityfor indoor composite propane cylinders andreviewed previous work performed byNPGA to gain approval for indoor use,reviewed international experience withindoor propane cylinders, and met with fire-fighters and fire safety experts to identifypotential concerns regarding indoor use. 25

Phase 2—Develop testing protocols andperformed fire testing of composite pro-pane cylinders for use with portable heatingappliances. 26

U.S. DEPARTMENT OFTRANSPORTATION

The U.S. Department ofTransportation (DOT) cur-rently allows compositecylinders for transportationby motor vehicle, rail freight, cargo vessel, andcargo aircraft under a special permit.

Both the Lite Cylinder Company and Ragascoversions of the cylinders are authorized fortransportation by DOT special permits. 27

These permits authorize the manufacture, sale,and use of composite cylinders for the follow-ing hazardous materials:

• Compressed gas, flammable, n.o.s. (Divi-sion 2.1), UN1954

• Compressed gas, non-flammable, n.o.s.(Division 2.2), UN1956

• Liquefied gas, flammable, n.o.s. (Division2.1), UN3161

• Liquefied gas, n.o.s. (Division 2.2),UN3163

• Liquefied gases, non-flammable chargedwith nitrogen, carbon dioxide or air, (Divi-sion 2.2), UN1058

• Petroleum gases, liquefied, (Division 2.1),UN1075

The safety and control measures required byDOT under these special permits are very spe-cific. Requirements include manufacturing inaccordance with American Society for Testingand Materials (ASTM) standards. DOT alsorequires production testing, random lotinspections, and other testing criteria whichwere extracted from existing standards includ-ing:

• British Standards Institution—EN 12245,Transportable Gas Cylinders—FullyWrapped Composite Cylinders (2002).

• International Standards Organization—ISO 11119-3, Gas Cylinders of CompositeConstruction (2002).

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• US DOT FRP-1, Basic Requirements forFiber reinforced Plastic (FRP) Type 3FcComposite Cylinders.

The primary testing requirements extractedfrom these standards cover:

• High temperature creep test maintainingtest pressure for 1,000 hours

• Leak test under pressure

• Permeability test

• Flawed cylinder test

• Drop test

• Torque test on the cylinder neck boss witha fitted valve

• Water boil test—the cylinder is subjectedto boiling water for 100 hours.

DOT also requires composite cylinders to beequipped with pressure relief devices in accor-dance with 49 CFR Section 173.301 (f). Com-posite cylinders are limited to a 15 year lifecycle and require requalification by visualinspection and proof pressure tests every 5years.

While DOT’s special permit testing require-ments are rigorous, it is important to note thatDOT testing requirements are designed onlyfor the safety analysis of the hazards and risksassociated with transportation in commerce. Inother words, DOT’s safety analysis of compos-ite cylinders did not consider the hazards andrisks associated with consumer safety, which isoutside the scope of the DOT’s authority. DOTalso does not approve steel or aluminum cylin-ders for consumer safety. DOT does specifythat any composite cylinder that has been sub-jected to fire may not be returned to service.

NATIONAL LIQUEFIED PETROLEUM GAS CODE

The current edition of Liquefied PetroleumGas Code (NFPA 58) 2004 does not specificallyprohibit composite cylinders. 28

In 2005 the propane industry proposed revi-sions to NFPA 58 that would allow compositecylinders to be used indoors in conjunctionwith portable unvented cabinet heaters havinga maximum output rating of 10,000 btu/hr.This proposal is scheduled for a vote by mem-bers at the NFPA’s World Safety Conference,June 6-7, 2007, Boston, Massachusetts. 29

The following key points summarize the pro-posed changes to NFPA 58 concerning com-posite cylinders and cabinet heaters for indooruse. 30 31

• Composite cylinders that are containedwithin and connected to listed cabinetheaters shall be permitted to be usedindoors only in one and two familydwellings and in businesses.

• Only composite cylinders will be permit-ted for indoor use, and those cylindersmust be Listed.

• Cabinet heaters shall be Listed. The intentof this section is to ensure that manufac-turers meet fire safety requirements estab-lished by a third party listing agency. The American National Standards Insti-tute (ANSI) is presently developing a new standard on cabinet heaters (ANSI

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Figure 7 National LP Gas Code.

Z1.11.3) which is expected to be releasedin 2007.

• Cabinet heaters shall have a maximumrating of 10,000 btu/hr.

• Composite cylinders are required to havepressure relief valves and are prohibitedfrom being equipped with a fusible plug.

• Composite cylinders used with cabinetheaters shall have a maximum capacity of16 pounds (7.3 kg) of propane (nominal 41lb or 19 kg water capacity). The intent ofthis section is to reduce fire loading insidestructures and to reduce the possibilitythat a standard 20 lb metal cylinder will beillegally adapted to a cabinet heater.

• Composite cylinders are required to havean overfill prevention device installed foruse with cabinet heaters and shall beequipped with a CGA793 connection. TheCGA793 connection is unique and de-signed for use only with the approved 16lb composite cylinder. The intent of thisrequirement is to ensure that the appli-ance side of the connection for use withcabinet heaters indoors cannot fit stan-dard 20 lb metal cylinders approved foroutdoor use.

• The maximum filling limit by weight ofpropane in a composite cylinder in non-engine fuel applications shall be 39.5 per-cent of the water capacity in pounds of thecylinder.

• Modification of the cabinet heater CGAconnection or the use of an adapter thatallows an alternate fuel source or cylinderto supply the cabinet heater shall be pro-hibited.

• The composite cylinder shall be located ina separate compartment from the heatingelement.

• Cabinet heaters shall utilize a two stageregulator that shall not be equipped witha pressure relief valve in either stage.

FIRE TESTING OF COMPOSITE CYLINDERS

THE BATTELLE FIRE TESTS

In 2005 Battelle and ThermDyne performedfire testing of six conventional steel cylinders,18 two-piece, linerless composite cylinders,and 11 one-piece composite, lined cylinderswith various fire exposure conditions, orienta-tions (vertical and horizontal), and fill levels. 32

Based on input from the Advisory Panel onComposite Propane Cylinder Testing, threefire conditions were selected for preliminarytests. 33 These included:

1. Fire A—This test subjected the edge of thecylinder to a lazy, very luminous flame.Three burners were placed 7 inches from theside, 6.5 inches up from the cylinder bottomwith a burner fuel pressure of < 1 psig.

2. Fire B—The test subjected the cylinder to aslightly more intense jetting flame. Threeburners were set 7 inches from the cylin-der’s side, 6.5 inches up from the cylinderbottom with a burner fuel pressure of 2 to 3psig.

3. Fire C—This test was even more intensethan test A & B. A jetting flame was arrangedwith three burners 16 inches from the side,6.5 inches up, with a burner fuel pressure of5 psig.

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Figure 8 Preliminary fire tests conducted by Battelle.

In the preliminary testing the cylinders wereeither oriented vertically or horizontally. In thehorizontal position the flame was directed atthe side, at the valve, or at the base. 34

The following summarizes the key findings ofthe Propane Education & Research Councilfunded fire tests conducted by Battelle:

• Steel Cylinders—None of the steel cylin-ders ruptured. All of the six steel cylinderstested emptied before the cylinder wallssoftened and thinned enough to rupture.One cylinder showed a bulge. All of therelief valves opened at 375 to 400 psig.Some pressure relief valves reclosed above300 psig while others did not reclose until100 psig.

• Composite Two-Piece Cylinders—Whentested in the vertical position with a filllevel of 75%, none of the linerless compos-ite two-piece cylinders failed. During thetests propane began to leak around thevalve to cylinder connection and diffusedthrough the cylinder walls after reachingpeak pressures between 98 and 118 psig.The outer protective jacket was consumedon all composite cylinder tests. One of thecylinders tested in the vertical positionfilled to a level just below the first joint onthe two-piece cylinder failed at the joint.

Nine of the two-piece cylinders testedwere equipped with pressure relief valves.Only one of these PRV’s opened. This testwas designed to create direct flameimpingement on the PRV with the cylin-der in the horizontal position. 35

When the two-piece cylinder was tested inthe horizontal position at the mediumflame setting, the cylinder ruptured andseparated into two pieces. Similar resultswere obtained in additional tests. It isimportant to note that these failures werenot violent ruptures. The fire rapidlyincreased in intensity but there was nofragmentation typical of a Boiling Liquid

Expanding Vapor Explosion (BLEVE).

• Composite One-Piece Cylinders—Theone-piece cylinders did not rupture whensubjected to similar tests. All of the cylin-ders were equipped with pressure reliefvalves. All of the cylinders were alsoequipped with fusible plugs rated at(266ºF) 130ºC and opened if the flameimpacted the valve area. 36

NASSAU COUNTY FIRE TESTS

In 2005 the Nassau County (New York) FireAcademy conducted live fire tests on compos-ite Liquefied Petroleum Gas (LPG) cylinders. 37

Two separate tests were conducted using two-piece 20 lb composite cylinders filled to 80%capacity with propane.

1. Burning Pool Fire—The test was set up as apool fire using burning fuel oil. The cylinderwas placed vertically on a metal grateapproximately 5 inches above the liquid. Atthree minutes the outer protective casingburned away and the pressure relief valvefunctioned in 3 minutes and 25 seconds.Because the resulting jet was very low veloc-ity, it is likely that the valve seals failed dueto the heat rather than the valve openingdue to pressure. At four minutes the cylin-der vented at the neck of the cylinder, andthe tank shell breached at four minutes and

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Figure 9 Burning pool fire test of two-piece composite cylinderconducted by Nassau County, NY.

25 seconds, resulting in a complete burn offof the propane. There was no BLEVE andthe cylinder remained upright during theentire test.

2. Pressure-fed Propane Fire—The test wasdesigned to create a pressure-fed propanefire with direct flame impingement onto thecylinder. At less than one minute the outerprotective casing burned away. The pres-sure relief valve functioned at two minutesand continued venting for three minutes.There was no breach of the cylinder shell.The cylinder burned off completely in 14minutes.

The Nassau County Fire Academy made thefollowing observations from their fire tests:

• The composite cylinder’s potential toBLEVE is remote. The cylinder wall can bebreached by fire without catastrophicdestruction of the cylinder.

• A large plume of fire can be ventedthrough the breach in the tank shell whenthe composite material burns through theshell.

• The pressure relief valve on the compositecylinders tested was the same as found onmetal cylinders. When sufficient heat wasapplied to the area of the cylinder’s neckthe composite shell opened and the firevented from around the attachment pointwhere the valve is screwed into the cylin-der. The valve remained in place but thefire vented around the attachment point.

FIRE TESTING OF CABINET HEATERSWITH COMPOSITE CYLINDERS

In 2005 Underwriters Laboratories, Inc. (UL)investigated the fire performance of compositepropane gas cylinders with cabinet heaters in aroom. 38 39 UL designed and conducted fivedifferent tests. Both one and two-piece designswere tested. These included the one-piececylinder with a non-load bearing liner, and a

two-piece unlined cylinder. The test designsand results are summarized below.

1. Empty Cylinder Fire—Empty one and two-piece composite cylinders were burned todetermine their heat and smoke releaserates as well as melting and dripping char-acteristics. Cylinders were placed verticallyand exposed to a standard test igniter. 40

Key Findings:

• The maximum heat release rates fromignition and burning of the empty cylin-ders were approximately 110 to 120 kW.

• Both the jacket and resin material con-tributed to the fire. Flames attached to thejacket of the one-piece cylinder in 20 sec-onds, and to the two-piece cylinder in 30seconds.

• There was pooling and burning of themelted resin. The size of the pool was 3 ft2

for the one-piece cylinder and 1 ft2 for thetwo-piece cylinder.

2. Cabinet Heater with Composite CylinderFire Inside a Room—A cabinet heater wastested in an NFPA 286 configuration roomwith the cylinder exposed to a standardigniter. 41 The room was lined with gypsumwallboard. The cabinet heater was locatedin the corner of the room facing the opendoorway. In one test, an additional sparecylinder was positioned next to the heaterand was also exposed to the igniter. Duringthe test, temperature increases and heat fluxwere measured inside the test room, as wellas the gas cylinder.

Key Findings:

• In each of these fire tests the ignited com-posite cylinder in the cabinet heater as-sembly released gas resulting in flash-over conditions in the room.

• Once the cylinder started to leak, therelease of gas continued during the test. A full cylinder was emptied in approxi-

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mately 10 to 15 minutes after the maxi-mum pressure was reached.

• Cylinder design may play a role in its fireperformance. The two-piece compositecylinder ruptured when partially filledand was oriented horizontally. The one-piece composite cylinder did not rupturein any of the tests conducted.

3. Cabinet Heater with Composite CylinderFire Inside a Room with Flashover—In thistest the room was lined with medium den-sity fiberboard. The cabinet heater andpropane filled composite cylinder wereplaced against the wall facing the opendoorway. A propane burner located in thecorner of the room was used to ignite thefiberboard and allowed to burn to flashoverconditions inside the room. 42 The increase

in temperatures from the fire growth weremeasured and the performance of the cabi-net heater were evaluated.

Key Findings:

• In a growing room fire that goes to flash-over, the composite cylinder breached andignited after the flashover occurred.Typically, there was a 3 to 5 minute lagbetween room flashover and breach of thecylinder. The leaking gas cylinder involv-ing the one-piece cylinder did not rupture.

4. Cabinet Heater with Composite Cylinderand Additional Spare Cylinder with FireIn a Corner—In this test the room was linedwith gypsum wallboard. The cabinet heaterwas placed opposite the open doorwaywith a full spare cylinder next to it. A steady

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Figure 10 Cabinet heater with composite cylinder fire inside a room.

Before

After

Before

After

300 kW fire was set in one corner of theroom. The pressure inside the cylinder wasmeasured and the cylinder was observed todetermine if the composite material ignited.

Key Findings:

• The spare cylinder’s pressure increasedfrom 106 psig to a maximum of 231 psigafter 30 minutes of exposure to fire in theroom. The pressure in the cylinder insidethe cabinet heater remained fairly con-stant with a maximum of 123 psig.

• The cylinders did not ignite and did notleak.

5. Burning Cylinder Filled With Water—Aone-piece cylinder was filled to half of its

rated capacity with water and then pressur-ized with nitrogen following a pre-deter-mined pressure—time curve. Two test sam-ple igniters were used (See footnote #41).When the cylinder reached 220 psig, sixminutes into the test, it was impacted with ahose stream. 43

Key Findings:

• A breach occurred in the cylinder at 4 min-utes and 12 seconds after ignition beforewater from the hose stream was applied.

• The burning one-piece composite cylinderpressurized with nitrogen did not breachviolently or rupture when impacted witha hose stream.

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Figure 11 One-piece construction composite cylinders fire test.

Before

After

VIEWPOINTS ON FIRE SAFETY

While propane composite cylinders havewidespread use and acceptance outside theU.S., their use within the U.S. is relatively new.Consequently, other than the testing describedin this paper, there is little practical field expe-rience in the U.S. concerning their fire safety.

As with any new products, there are both sup-porting and opposing viewpoints concerningsafety. The following key points summarize thefindings of the authors based on discussionswith members of industry and the fire serviceas well as the results from feedback obtainedthrough the Advisory Panel on Composite Pro-pane Cylinder Fire Testing and NFPA Regionalmeetings as reported by Battelle. 44 45

SUPPORTING VIEWPOINTS

• Composites have been used for manyyears in various structural componentswhere safety is an issue. Examplesinclude the marine, automotive, and air-craft industries. Composite cylinders forpropane service have advantages overother materials such as metals including:strength, corrosion resistance, lightweight, and the ability to actually see thelevel of propane inside the cylinder.

• Proposed code changes to NFPA 58 con-cerning propane cabinet heaters andcomposite cylinders are adequate to pro-vide for safe use indoors. The 16 poundcomposite cylinder and connection areuniquely designed for connection to cab-inet heaters, thereby eliminating the pos-sibility that a larger composite or metalcylinder can be adapted and connected tothe heater, and the heater is limited to10,000 BTU/Hr.

• Composite propane cylinders exposed toindirect or direct flame impingement onthe cylinder will not produce a BoilingLiquid Expanding Vapor Explosion(BLEVE). From a firefighter safety per-

spective, this is good news. Not everymetal cylinder subjected to direct flameimpingement results in container failureby BLEVE. Some cylinders simply burnoff the propane through the pressure reliefvalve, while other cylinders may open upand vent through a split in the tank shell.Firefighters have been killed or seriouslyinjured from metal propane cylinder fail-ures by BLEVE. 46 Composite cylindersmay have safety advantages as comparedto metal cylinders. 47

• If approved by the National LP Gas Code(NFPA 58) as currently proposed, proper-ly designed propane unvented cabinetheaters, when combined with compositecylinders, may present some safety ad-vantages over other types of space heatersalready approved for indoor use in occu-pied buildings; e.g., kerosene heaters. Thismay be especially true when issues suchcarbon monoxide or accidental or inten-tional cross fueling is considered; e.g.pouring gasoline into a kerosene spaceheater. Propane is a clean burning non-toxic flammable gas.

• The availability to consumers of listedcabinet heaters may reduce the possibilitythat appliances approved for outdoor usewill not be brought indoors. Experiencefrom long term power outages has shownthat some residents bring outdoor appli-ances like propane gas grills indoors forspace heating or cooking food. 48 Theavailability of propane cabinet heaters ap-proved for indoor use may reduce fatalitiesresulting from carbon monoxide duringnatural disasters such as hurricanes andwinter storms.

OPPOSING VIEWPOINTS

• Allowing cabinet heaters and propanecomposite cylinders inside residentialoccupancies results in increased fire load-ing in compartmented spaces. Even small

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composite cylinders in the 16 to 20 poundrange can create dangerous conditions forfirefighters making interior structural fireattacks if they breach when firefightersshare the same space within a room.

• Even with proper design and safety fea-tures, allowing unvented cabinet heatersinside residential occupancies, regardlessof the type of cylinder (composite ormetal), there is an increased safety riskfrom carbon monoxide exposure. There isconcern over maintenance issues associat-ed with all types of space heaters, not justpropane appliances. Allowing propaneheating appliances indoors in occupiedspaces simply adds another potentialsource for carbon monoxide poisoning. 49

• There currently is no national consensusstandard available to guide manufactur-ers and fire safety enforcement agenciesin determining if a cabinet heater enteringthe U.S. marketplace is safe. The Ameri-can National Standards Institute (ANSI)is presently developing a new standardon cabinet heaters (ANSI Z21.11.3) whichis expected to be released sometime in2007. Propane cabinet heaters should notbe allowed inside occupied buildingsuntil a standard has been issued and anopportunity for public comment has beenprovided.

SUMMARY

Composite materials are not new and compos-ite cylinders have been in use for several yearsoutside the United States. They have recentlybeen introduced into the U.S. and are ap-proved by the U.S. Department of Transpor-tation for transportation by highway, marine,rail, and cargo aircraft. Composite cylindersare currently allowed under the National LPGas Code for outdoor use only. As notedabove, they are being proposed for indoor use

in conjunction with a heating appliance knownas a cabinet heater.

Composite cylinders are presently manufac-tured in a one and two-piece design. They arebasically made from a polymer wrapped fiber-glass with an outer casing designed to provideadditional protection to the tank shell. Con-struction materials include polyacrylonitrilebutadiene styrene (ABS), high-density polyeth-ylene (HDPE), and polyethylene terephthalate(PET). Both the one and two-piece designs areequipped with a Pressure Relief Valve set tofunction at 375 psig. The most common sizesbeing manufactured are the 20 pound BBQcylinder and the 33 pound forklift cylinder. A16 pound version would be manufactured foruse with cabinet heaters if they are approved.

Recent fire tests conducted in 2005–2006 bythree different respected organizations indicatethat composite cylinders will not BLEVE whenexposed to direct flame impingement. Com-posite cylinders may reduce the risk to fire-fighters by eliminating the threat from BLEVE,but tests indicate that they will breach in a fire.Essentially, the propane vents and burnsand/or diffuses through the cylinder wall. Theremaining composite melts and burns until itself extinguishes.

Proposed changes to the National LP GasCode (NFPA 58) will allow propane cabinetheaters and composite cylinders in occupiedbuildings. This issue will be considered beforethe National Fire Protection Association An-nual Meeting in Boston, MA on June 6–7, 2007.Emergency responders and fire marshals needto be well informed of the fire safety issuesassociated with composite cylinders and cabi-net heaters. Fire safety professionals will needto determine if they will support suggestedchanges to the National LP Gas Code and if thecode is adequate enough to provide an accept-able level of fire safety for U.S. citizens.

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1 Mike Hildebrand and Greg Noll are emergencyresponse and planning consultants with Hilde-brand and Noll Associates, Inc., Port Republic,Maryland. They are the authors of PropaneEmergencies, 3rd edition (2007) and Chapter 8-7,Public Fire Protection and HazMat Management, 20thEdition of the NFPA Fire Protection Handbook(2007). They are both members of the NFPA-472Committee, Standard for Professional Competence ofResponders to Hazardous Materials Incidents. Contactthe authors at [email protected] [email protected].

2 The Propane Education & Research Council wasorganized in 1996 through legislation authorizingan assessment of each gallon of propane gas at thepoint it is odorized or imported to the U.S. Thismulti-million dollar investment by the propaneindustry is used to improve consumer safety, fundnew research and development of new and moreefficient propane equipment, and to expand publicawareness of propane. In 1998 PERC funded thedevelopment of the Propane Emergencies trainingprogram, consisting of a textbook, companionFacilitator’s Guide and video. The Propane Emer-gencies training program is now in its third editionand has been distributed free of charge to over30,000 emergency responders. The expanded pro-gram is now available for a nominal charge. Formore information consult www.propanesafety.comand click on Propane Emergencies.

3 U.S. Department of Transportation—approvedpressure vessels have been manufactured for over18 years using a variety of composite overwraps in an epoxy resin. These include fiberglass, aramid,and carbon and Kevlar® fiber. Materials typicallyshipped and used in these types of cylindersinclude breathing air, normal compressed air, oxygen, hydrogen, and natural gas. For an inte-resting comparison of the strength of composite materials vs. steel and aluminum consult www.bactechnologies.com and click on Design.

4 Source: Goodrich www.epp.goodrich.com. Theearliest known composite material is a simpleadobe brick. Straw (a fibrous material) is mixedwith mud (an adhesive with strong compressionstrength). Another common example is plywood.Today, composite materials are widely used in theautomotive industry. For example, the entire body

of the Chevrolet Corvette is made from compositematerials. The Boeing 777 uses various compositematerials in its structure because of their strengthand weight saving abilities.

5 Source: The Aviation History On-Line Museum.

6 Source: Goodrich www.epp.goodrich.com.

7 Source: The Lite Cylinder Company www.litecylinder.com.

8 According to one manufacturer, there are about240 million high pressure cylinders (both metal andcomposites) in operation in the world today andabout 60 million more are being manufacturedannually. There are about 1.5 million compositecylinders in the world market today and the poten-tial market size is estimated at 10 million. Source:Kompozit-Praha Company. See www.kompozit-praha.cz/en/company.html

9 Cylinders are marked with the maximum amountof water that can be stored in the cylinder, but aretypically referred to by the maximum amount ofpropane that can be stored in them. For example, a100-pound propane cylinder can safely store 100pounds of propane but would be marked with awater capacity (w.c.) of 239 pounds.

10 Source: Composite Propane (LP Gas) Cylinders,November 17, 2005, Minnesota Department ofPublic Safety, State Fire Marshal.

11 The National Fire Protection AssociationLiquefied Petroleum Gas Code (NFPA 58) is beingrevised for release in 2007. The National PropaneGas Association has made several proposals tomodify NFPA 58 to allow cabinet heaters with com-posite cylinders.

12 EN 12245, Transportable gas cylinders, Fullywrapped composite cylinders, and InternationalStandards Organization (ISO), ISO11119-3–GasCylinders of Composite Construction— Specifica-tion Test Methods—Fully Wrapped Fiber Rein-forced Composite Gas Cylinders with Non-LoadSharing Metallic or Non-Metallic Liners.

13 Composite cylinders are regulated by DOT un-der 49 CFR Parts 106, 107, and 171-180. They areexempted from 49 CFR Parts 173.304a (a) (1) and175.3.

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14 Pressure relief valves in both the one and two-piece cylinders are set to relieve pressure at 375psig.

15 Ragasco AS, Postboks 50, Raufoss IndustrialPark B306, N-2831 RAUFOSS, Norway. Call +47 6115 16 00. www.ragasco.com.

16 Kompozit-Praha, Dysina 298 3300 02 Dysina uPlzne, Czech Republic. Call +420 377 946 091.www.kompozit-praha.cz.

17 U.S. Department of Transportation, Pipeline andHazardous Materials Safety Administration,Permit for DOT-SP 12706, issued to Ragasco, AS.Raufoss, Norway on March 16, 2006, Washington,D.C.

18 The Lite Cylinder Company, 139 SoutheastParkway Court, Franklin, Tennessee 37064. Call866-842-5483. www.litecylinder.com.

19 U.S. Department of Transportation, Pipeline andHazardous Materials Safety Administration,Permit for DOT-SP 13957, issued to T.L.C.C., Inc.,Franklin, Tennessee on February 3, 2006,Washington, D.C.

20 Source: Rodney Osborne, Composite PropaneCylinders Current and Future, Battelle, August 25,2005.

21 National Petroleum Gas Code, NFPA 58 (2004),Quincy, MA.

22 PERC Docket Number 10662—CompositePropane Cylinder Regulatory Approval Request. A copy of the Docket can be viewed at http://www.propanecouncil.org/rd/cylinder.html

23 PERC Docket Number 11328—Code Approval ofComposite Propane Cylinders for Indoor Use.

24 Code Approval of Composite Cylinders forIndoor Use—Phase-2, Docket 11643, Testing Reportsubmitted by Stephanie Flamberg, Rodney Os-borne, and Susan Rose, Battelle, Columbus, Ohio.April 2006.

25 In 2005 Battelle attended NFPA Regional FireCode meetings in Nevada, Maryland, Colorado,and Georgia to obtain feedback on the proposedfire testing program.

26 Battelle contracted with National Fire ProtectionResearch Foundation to establish a committee offire protection officials to aid in the development ofa detailed fire testing protocol. The technicalAdvisory Panel for this project included key repre-sentatives of the NFPA 58 committee, theInternational Association of State Fire Marshals(NASFM), and other technical specialists. Thepanel consisted of 8 people who were involved inreviewing the test plans, witnessing the fire testingand guiding the project. Battelle and ThermDyneperformed preliminary fire testing for the projectfrom February 17 to March 3, 2005 at the MiningResource Engineering Limited test site north ofKingston, Ontario, Canada. Following these tests,Battelle contracted with Underwriters Laboratories(UL) to conduct live fire testing of compositepropane cylinders in conjunction with the heatingappliance in an NFPA 286 configuration test room.This research was completed by UL in November2005.

27 For more information on DOT special permits go to the Hazardous Materials Homepage athttp://hazmat.dot.gov/sp_app/special_per-mits/spec_prem_index.htm. Click on SpecialPermits and Approvals.

28 National Petroleum Gas Code, NFPA 58 (2004).National Fire Protection Association, Quincy, MA.See www.nfpa.org.

29 Report of the Motions Committee on CertifiedAmending Motions for the Fall 2006 CycleDocuments, November 15, 2006, National FireProtection Association, Quincy, MA.

30 Under the proposed NFPA 58 (2007) Section3.3.11, a cabinet heater is defined as a portableunvented type heater with a self-contained LP-Gassupply.

31 Under the proposed NFPA 58 (2007) Section3.3.17.1, a composite cylinder is defined as a cylin-der constructed with fully wrapped fiber reinforcedmaterial, or a two part adhesively bonded non-metallic cylinder.

32 Material in this section is based on tests fundedby the Propane Education & Research Council(PERC) under Docket 11643. The tests were com-pleted by Battelle from February 17 to March 3,

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2005 at the Mining Resource Engineering Limited’stest site north of Kingston, Ontario, Canada.

33 The Advisory Panel was made up from membersof the fire protection community. Representativesincluded the National Association of State FireMarshals, National Fire Protection Association,International Association of Fire Chiefs, Inter-national Fire Marshals Association, Fire ProtectionResearch Foundation, Underwriters Laboratories,North Carolina Department of Agriculture,Phoenix Fire Department, and the National Pro-pane Gas Association.

34 Code Approval of Composite Propane Cylindersfor Indoor Use, Testing Report, Docket 11643, byStephanie Flamberg, Rodney Osborne, and SusanRose. April 2006, Battelle, Columbus, Ohio. Table 2on Page 6 provides a detailed breakdown of eachcylinder, its configuration during the fire test and ifit was equipped with a PRV or fusible plug.

35 The results of the preliminary fire tests of thecomposite cylinders showed that there was no sig-nificant difference in performance between two-piece cylinders equipped with pressure reliefvalves and those that did not.

36 The fire tests included fusible plugs to evaluatetheir performance under live fire conditions. Theproposed changes to the 2007 edition of NFPArequire composite cylinders intended for use withindoor cabinet heaters to have a pressure reliefvalve, but they will be prohibited from having afusible plug.

37 Composite LPG Cylinder Test Burns: No BLEVE,by Assistant Chief Dennis Murphy and DeputyChief Gene Pietzak, Firehouse.com, November 20,2006. For a copy of this article follow the link to:http://cms.firehouse.com/content/article/article.jsp?id=52063&sectionId=18.

38 Material discussed in this section is based onwork funded by the Propane Education & ResearchCouncil under contract with Battelle. All tests werecompleted by Underwriters Laboratories, Inc. SeeResearch Investigation on the Fire Performance ofComposite Propane Gas Cylinders: Final Report,November 22, 2005, Project 05CA34146 by MariaHjohlman, Underwriters Laboratories, Inc.,Northbrook, IL.

39 The cabinet heater used in the UL fire tests wasdesigned and manufactured in Europe and rated at20,000 btu/hr (5.9 kW). The outer dimensions ofthe heater were 16-1/2 inches by 17-1/2 inches by27-1/2 inches high. The heater included a rubberhose and a hose clamp for connection to a regulatorthat incorporated a cylinder valve connection. Atwo-stage regulator meeting UL 144 was connectedto the cylinder using a QCC1 fitting meeting CGA791 standards. This system incorporated excessflow and thermal shutoff protection. In one test theCGA E-1 025 connected to the regulator without theother fittings. The heater was left in the ON posi-tion in some tests and OFF in other tests.

40 The standard test igniter consisted of a 3 inchdiameter by 6 inch long cellulosic roll placed in aplastic bag filled with 8 fluid ounces of gasoline tosoak the cellulosic roll.

41 Standard Methods of Fire Tests for EvaluatingContribution of Wall and Ceiling Interior Finish toRoom Fire Growth, NFPA 286, 2006, National FireProtection Association, Quincy, MA.

42 UL used a 300 kW or a 40-60 kW propane burn-er to ignite the fiberboard.

43 The hose stream was a 1-1/2 inch rubber hoseequipped with an Elkhart SLO/0 adjustable nozzle.The nozzle was set at a maximum flow usingstraight stream at 100 psig. The stream was aimeddirectly at the cylinder from a distance of 18 feet.

44 The authors have taken a neutral position oneither the advantages or disadvantages of propanecomposite cylinders or cabinet heaters. The obser-vations in this section, pro or con, do not necessar-ily reflect the view of the authors.

45 Code Approval of Composite Cylinders forIndoor Use—Phase-2, Docket 11643, Testing Re-port, Pages 2-3, as submitted by StephanieFlamberg, Rodney Osborne, and Susan Rose,Battelle, Columbus, Ohio. April 2006.46 Since 1993 seven firefighters have been killed inthree separate BLEVE incidents in the U.S. andCanada involving non-stationary metal LPG tanks.Source: Propane Emergencies, 3rd, by MichaelHildebrand and Gregory Noll, page 159, Red HatPublishing (2007).

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http://cms.firehouse.com/content/article/article.jsp?id=52063&sectionId=18

47 In December 2006 one of the worst winter stormsto hit the northwest U.S. in over a decade knockedout power to more than 1.5 million homes and busi-nesses. There were 6 fatalities and 100 injuries fromcarbon monoxide poisoning in separate incidentsin Washington and Oregon. These accidents werecaused when people brought unapproved appli-ances such as BBQ grills, charcoal grills, spaceheaters, and generators indoors to heat their homesand cook. At least 55 of these people requiredadvanced medical treatment in hyperbaric cham-bers where pressure was used to force oxygen intotheir blood. Multiple Sources: December 17–18,2006—Seattle Times, CNN, USA Today, andFirehouse .com.

48 In the aftermath of Hurricane Katrina (2005)there were 51 cases of carbon monoxide poisoningrequiring treatment at hyperbaric chamber treat-ment facilities in Alabama, Mississippi, andLouisiana. Between August 29 and September 24there were 5 fatalities and 46 nonfatal CO poison-ings. The majority of these poisonings were causedby bringing a generator into the home to provideelectrical supply for lighting and cooking appli-ances. Source: U.S. Center for Disease Control asreported by N.B. Hampson, MD, Center forHyperbaric Medicine, Virginia Mason MedicalCenter, Seattle, Washington. M.W. Lai, MD,American Association of Poison Control Centers.M. McNeil, MD, PhD, P. Byers, MD, MississippiDepartment of Health. R. Ratard, MD, LouisianaOffice of Public Health. M. Patel, MD, M Belson,MD, A Stock, PhD, J. Ferdinands, PhD, R. Funk,DVM, P. Meyer, PhD, C. Pertowski, MD, NationalCenter for Environmental Health; D. Crocker, MD,EIS officer, CDC.

49 For a good overview of carbon monoxide and itshazards visit the U.S. Environmental ProtectionAgency Indoor Air Quality Web site at: http:/ /www.epa.gov/iaq/co.html.

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