poxy Intumescent Coatings(EIC) have been used exten-sively on offshore andonshore petrochemicalinstallations to protect thestructural integrity of steel

in the event of a fire. In response to intenseheat, EIC materials first soften then releasegases, which transforms the coating into achar much thicker than the original coatinglayer with cellular insulation properties. EICprevent or delay structural failure, allowingtime for evacuation of personnel, and foremployment of active fire fighting measures.EIC can also reduce asset loss and help min-

PCE December 1996 Copyright ©1996, Technology Publishing Company16

imise environmental damage.Recent years have brought dramat-ic changes on how EIC are beingspecified, driven by both changingsafety philosophies in the petro-chemical industry and by econom-ic considerations.

Fire safety covers an enormousfield. There are volumes of codes,guidelines, and regulations underthe control or influence of variousgovernmental departments, tradeorganisations, and insurance com-panies, with each country actingindependently. Understanding the

EpoxyIntumescentCoatings: Current Philosophy

by Thomas Ward

and Paul Greigger,

PPG Industries, Inc.,

Springdale, PA, US;

Ron Matheson,

PPG Industries, Inc.,

Aberdeen, UK;

and Bjørn-Erik Alveberg,

Jak J. Alveberg a.s,

Østerås, Norway

Fig. 1: Application of EIC to prefabricated steel. The bulk of the application can be in theshop before the steel is erected. Small “tie-in” areas are masked and coated after the structureis built. The flexibility, toughness, and fast cure of EIC allow the precoated steel to be movedand installed without damage.

System. The next step is to predictstructural integrity and collapsescenarios; for this work, the soft-ware programme called USFOS(SINTEF Structures and Concrete,Trondheim, Norway) is utilised.

The consequence of structuralfailure is evaluated using severalcriteria. Evacuation of personnel isof prime importance to allow timeto reach designated safe refuge.The collapse of supports for criti-cal processing equipment mayresult in additional inventoryrelease or pose a hazard to person-nel or other equipment. The criti-

17PCE December 1996Copyright ©1996, Technology Publishing Company

cal structural members are identi-fied; the time needed to preventcollapse is determined; and thefire environments are defined togenerate specifications for EICrequirements.

The fire safety assessments areallowing design and safety special-ists to target critical areas for pro-tection to ensure survival in thefire and blast scenarios developed.An added benefit is a cost andweight reduction in the use of EICbecause it is no longer being spec-ified for non-critical structuralmembers. Through better design,isolation of critical areas, and useof emergency shutdown systems,excess passive fireproofing hasbeen eliminated.

Brief History of Fire RatingsHistorically, the testing of fire-

rated materials or constructionsuch as fire doors, floors, and pen-etrations was carried out underfire conditions simulating a cellu-losic fire. Several fire standardswere developed, including ASTME-119; UL 263; BS 476, Part 21;and ISO 834. These standards con-tinue to be used throughout theworld. During the 1970s, thehydrocarbon processing industryinvestigated the fire conditionsproduced by burning varioushydrocarbon materials. Twoimportant variables emerged todistinguish a hydrocarbon from acellulosic fire. The heat-up rate, asdepicted in Fig. 3, shows a hydro-carbon fire will reach 1100 C with-

Define Fire Hazard

Calculate Structural Thermal Response

Structural Failure Times Predicted

Consequence of Structural Failures

Identify Structural Members toBe Protected by EIC

Determine Required Thickness of EIC

Fig. 2: Flow Chart Showing SafetyAssessment and EIC Requirements

fire protection requirements offacility owners operating in differ-ent countries has and continues tobe a difficult challenge for EICsuppliers. Because of non-specificor non-existent regulations, differ-ences in interpretation, variationsin facility owners’ safety philoso-phy, and diversity of methodologyemployed in safety assessments,the end result has been inconsis-tent specifications for EIC use.

Current Trends in Specifying EICFollowing the disastrous fire on

the Piper Alpha, an offshore plat-form in the North Sea, and thepublication of the Cullen report(Secretary of State for Energy, UK,1990), the petrochemical industryhas undergone rapid and evolvingchanges in both design and safetyconsiderations for offshore plat-forms, which are now being car-ried over to onshore facilities.

The Alliance concept on newprojects where the owner, engi-neering firm, fabricator, and othermajor sub-contractors form a part-nership to reduce project cost, isalso having an impact on the useof EIC. New methodologies arebeing employed to determinewhere and what quantity of EICmaterial is needed to protect aspecific facility.

The fire hazard assessmentidentifies where a fire could occur,its type (jet fire or hydrocarbon),its duration, based on availablefuel inventory, and its directionand distance from the source.

Programmes to model fire eventshave been developed for hydrocar-bon and jet fires. One example isthe programme Chaos from BritishGas. This information is used tomodel and predict the resultanttemperature rise of the structuralelements, using software such asAnsys or Swanson Analysis

PCE December 1996 Copyright ©1996, Technology Publishing Company18

in 5 minutes, while the cellulosiccurve reaches 880 C after 40 min-utes. Comparing heat fluxes, thecellulosic fire is approximately 100kW/m2 versus 200 kW/m2 for thehydrocarbon fire. The hydrocar-bon fire curve is known as UL1709, Mobil curve, or NorwegianPetroleum Directorate (NPD)curve.

In 1984, UnderwritersLaboratories (UL) in Northbrook,IL, US, tested the first EIC productusing the standard UL 1709,“Rapid Rise Fire Tests of

Protection Materials for StructuralSteel.” The testing was performedon a 10W49 steel I-beam taken toa failure temperature of 538 C. UL1709 test requirements alsoinclude exposing the EIC materialsto a series of accelerated weather-ing tests. The weathered samplesare fire tested and compared tounexposed samples to determine ifdegradation of fire properties hasoccurred. An ASTM E-84, UL 723,“Test for Surface BurningCharacteristics of BuildingMaterials,” is conducted to deter-

Classification Time (minutes) to Meet Backside Time (minutes) to Provide Integrity to Temperature Requirements1 Prevent Passage of Fire and Smoke and/or

to Provide Integral Load Bearing Capability

A-60 60 120

A-120 120 120

H-60 60 120

H-120 120 120

H-O2 120 120

Table 1: Summary of A & H Ratings for Bulkheads and Decks (A=Cellulosic; H=Hydrocarbon)

1 Failure criteria is when the average backside temperature readings reach 139 C or an individual reading reaches 180 C.2 The “O” Classification requirement is to prevent passage of fire and smoke and provide load bearing capability for 2 hours. But thecurrent specifications have set 400 C average temperature as the temperature requirement.

Cross Sectional PerimetreHp/A = ———————————

Cross Sectional Area

Fig. 4: Hp/A (F/A) Steel Sizes

High Hp/A Low Hp/A

0:00 0:05 0:15 0:30 0:45 1:00 1:15 1:30 1:45 2:00 2:30 3:00 3:30 4:00

1375

1100

825

550

275

Tem

pera

ture

, C

Time, hr:min

UL 263UL 1709

Fig. 3: Comparison of Hydrocarbon (UL 1709) vs. Cellulosic (UL263) Fire Heat-up Rate Curves

Fig. 5: Epoxy Intumescent Coatings provide fire and corrosion protec-tion to vessel skirts.

Copyright ©1996, Technology Publishing Company 19PCE December 1996

mine the flame spread and smokegeneration.

UL testing and listing proce-dures also include witnessing themanufacturing procedures for theproduct to be tested. UL retains onfile the manufacturing steps, rawmaterials or components (withcode numbers), and the supplierinformation. UL also provides afollow-up inspection service; itsinspectors will visit manufacturingsites, review manufacturingrecords, and, occasionally, takesamples for comparisons with theoriginal product that was tested.

In 1984, specifiers of EIC nowhad 2 fire scenarios at their dis-posal, one for cellulosic and onefor hydrocarbon fires. The ULdirectory listed the column testingunder ASTM E-119 conditions withan “X” designation followed by athree digit code and “XR” for UL1709 listing. The design listingincludes the hourly ratings andrequired thickness of EIC with adescription of the method of appli-cation.

In the early 1980s, the hydrocar-bon fire test requirement wasevolving; unfortunately, outside ofthe US, there was not an acceptedfire standard. Regulations andguidelines for specifying EIC wereadopted from the hydrocarbonprocessing industry, theInternational MaritimeOrganisation (IMO), and theInternational Convention for theSafety of Life at Sea (SOLAS).

The quest for a standardisedapproach to define fire testing con-ditions was occurring through the1980s; but there was disagreementamong interested parties trying toreach a consensus on a standard-ised test. The hydrocarbon firetesting being performed in Europe

which provide the required thick-ness of a specific EIC for a partic-ular Hp/A value for a specifiedtime period and steel failure tem-perature. A typical table is shownin Table 2.

Jet Fire TestingThe industry has become aware

of the need to protect against jetfires. A jet fire results from a highpressure hydrocarbon releasefrom a source such as a rupturedpipe, flange, or process vessel. Itis characterised by a high velocityflame and a heat flux of 300kW/m2.

Until recently, the only recog-nised test of jet fire resistance was

Structural Minimum dry film thickness to achieveElement Hp/A fire resistance time (mm)1

100 5 7 10 12 15 18110 5 7 10 13 16 19120 5 8 11 14 17 20130 5 8 11 14 17 20140 5 8 11 15 18150 5 8 12 15 18160 5 9 12 15 19170 5 9 12 16 19180 5 9 12 16 20190 5 9 13 16 20200 6 9 13 17 20210 6 9 13 17220 6 10 13 17230 6 10 13 17240 6 10 14 18250 6 10 14 18260 6 10 14 18

Time (min) 30 60 90 120 150 180

Table 2: EIC Dry Film Thickness Required, Based on Hp/A Values1 Minimum dry film thickness necessary to restrict the temperature of steel cores to 400 Cwithin the specified time period as a function of the cross sectional area and shape of the struc-tural element represented by the Hp/A value, where “Hp” is the perimetre of the cross section ofthe element exposed to the fire in metres and “A” the area of the element in square metres.

followed a fire test time-tempera-ture curve referred to as theNorwegian Petroleum Directorate(NPD) Curve. In order to distin-guish between the 2 kinds of tests,“A” was designated for cellulosicand “H” for hydrocarbon fire con-ditions. Table 1 summarises themore common ratings used fordecks and bulkheads.

As a weight and cost savingsmeasure, the concept of using theHp/A values of structural mem-bers (Fig. 4) was utilised. Fire testsare conducted on structural mem-bers representing a range of Hp/Avalues coated with EIC tested todifferent failure times. The testdata is used to generate tables

PCE December 1996 Copyright ©1996, Technology Publishing Company

the British Gas facility atSpadeadam. The test consists of afree jet produced from sonicrelease of natural gas exiting anozzle at 3 kg/sec. The instru-mented test piece, usually an I-beam or tubular 10 m in length, ispositioned 9 m away from the jetnozzle. A 1-hour test would con-sume over 10,000 kg of gas. Thehigh gas velocity tests the erosionresistance of the fire protective

material.A jet fire working

group was formed ofmembers from indus-try, certifying agen-cies, and test labora-tories. They havedeveloped a smallscale jet fire test.This is described inthe “OffshoreTechnology Report,”OTI 95 634.7 Thisprocedure reducesthe scale and cost ofthe test, as comparedto the Spadeadamtest, but maintains itsseverity. The gas flow

rate is 0.3 kg/sec, using propanedirected to a target one metreaway. There is no currently recog-nised standard jet fire test,although this test procedure isnow being recognised by certify-ing agencies.

Because of the interim status ofthe test, certifying authorities,such as Lloyd’s and Det NorskVeritas (DNV), are issuing lettersof compliance rather than typeapprovals. Approvals for jet firerequirements are granted on aproject-by-project basis.

Explosion ResistanceIn many cases, a fire event will

be preceded by an explosion. Theexplosion may be insufficient todamage the structure but strongenough to dislodge the fireproof-ing. If the fireproofing is damagedor disbonded by the explosion,then the steel will not be ade-quately protected from fire. It iscritical that the fire protectivecoating demonstrate the ability towithstand an explosion at least assevere as the predicted overpres-sure. The fireproofing must notcrack or disbond as a result of theexplosion, and the fire perfor-mance of the product must not beimpaired as a result.

An explosion produces not onlyoverpressure but also impact dam-age from flying debris. If the fireprotective coating is brittle or doesnot have sufficient flexibility, thematerial may be severely dam-aged, not only by the explosionoverpressure, but by the impact ofdebris. Actual explosion testingcan determine the response of acoating to debris, whereas simu-lated explosion testing cannot.Because explosion resistance isimportant to the effectiveness of afire protective system, the fire test-ing performance of a productshould not be considered withoutdocumented blast test perfor-mance.

Current StatusA safety assessment as

described previously will predict afire scenario in a particular area ofa facility. If a jet fire event is pos-sible, such variables as availableinventory, initial pressure, andsize of a release opening are takeninto consideration. The availableinventory will be controlled byshut-down valves, volume of pro-cessing equipment, and blow

20

Fig. 6: Main structural elements of a deck are protected with EIC.Non critical secondary steelwork is partially protected (called a“coatback” to prevent heat transfer to the main member.

PCE December 1996Copyright ©1996, Technology Publishing Company 21

down capability. As the fuel pres-sure drops, the jet fire length,velocity, and heat flux will dimin-ish. As a result, direct jet fireimpingement will last only for aninitial time period. The heat fluxwill decrease from 300 kW/m2

down to 200 kW/m2, representinga hydrocarbon or pool fire. The fireexposure becomes a mixed event,initially a jet fire but later a hydro-carbon fire. The jet fire may lastfrom 15 minutes to several hours,depending on inventory, but, typi-cally, with other safety measuresin place, the jet fire is being pre-dicted to last 15 to 30 minutes.

Jet fire exposures from fire riskanalyses are being classified as jetfire only (J ratings in Table 3) oras a jet fire followed by a hydro-carbon or pool fire (J/H rating inTable 4).

Hydrocarbon fires, often referredto as “pool fires,” may result inlower heat fluxes if the structuralmembers in question are at vary-ing distances from the fire source.The heat fluxes may range frombelow 100 kW/m2 to greater than200 kW/m2. The complexity inspecifying a fire exposure type,heat flux and duration, differentstructural geometries, Hp/A val-ues, and assigned failure tempera-tures should now be very appar-ent. The task to generate therequired EIC thickness by actualfire testing is becoming unrealistic.

As described previously, fire sce-narios are much more preciselydefined and are unique to eachproject. Specifications for EIC byareas of a structure are thereforemuch more detailed than in previ-ous times. Because these newspecifications represent an infinitenumber of fire scenarios and struc-tural configurations, testing

becomes virtually impossible. Thetesting that is carried out providesthe cornerstone of a material’s fireresistance. Based on these stan-dard test results, it is possible,with an understanding of thermo-dynamics, risk analysis, and fireevents, to determine the requiredamount of fireproofing for specificfire scenarios.

Computer modelling of fire rat-ings can, if used properly, be auseful tool to determine appropri-ate thickness. These computertechniques are still in their infancyand should be used only to inter-polate from actual documentedfire test data. The use of computersimulation to predict fire perfor-mance of EIC in jet fires is stillunproven.

Criteria for Choosingan EIC Material

A list of criteria for selecting EICmaterial is shown below.• Fire Specification—Verify that theEIC material has been tested underthe specified fire environment andstructural member designs by arecognised fire testing laboratoryand the results have been certifiedby an approved organisation.Explosion resistance should also bedocumented.• Environment of Facility—The fol-lowing should be considered:

A. Location and Climate—Onshore or offshore, ambient tem-perature, severe temperaturechanges, rainfall, and humidity arefeatures which may effect the dura-bility of a product.

B. Physical Exposure—Possibledamage may result from objectscoming in contact with EIC, struc-tural movement, vibration, and sur-face operating temperature.

C. Chemical Exposure—Types ofchemicals and duration of exposure.Evaluation of these environmentalfactors are extremely important toensure that the EIC material will notbe easily damaged or degraded.• Application Properties—The EICmaterial must allow application overa large range of climatic conditionsand be user-friendly to allow easyapplication to large structures aswell as to small laboratory testpieces.• Technical Sales Support—Thesupplier should have the resourcesto provide support to the facilityowner and engineering firm duringthe specification stage. An exampleis assisting the customer by calcu-lating the amount of EIC needed asindicated in the blueprints.• Technical Field Support—Trainedtechnical field support personnel

FireClassification

(J/H) Fire Exposure & Duration

J-15/H-15 15 minutes jet fire exposure changing to 15 minuteshydrocarbon conditions

J-15/H-45 15 minutes jet fire exposurechanging to 45 minuteshydrocarbon conditions

Table 4: Summary of J/H Ratings

Fire Protection Time Classification to Meet Backside

(J) Temperature Requirements1

J-15 15

J-30 30

J-60 60

Table 3: Summary of “J” Ratings forBulkhead and Decks1 Failure temperatures are specific to eachdesign and safety assessment.

PCE December 1996 Copyright ©1996, Technology Publishing Company22

should be available at start-up toinstruct the application crew,QA/QC staff, inspectors, and facili-ty owner’s team members.• Economics—The calculation ofcost should include not only theinstalled cost for material andlabour also but the maintenance/repair cost over the projected lifeof the facility to arrive at a totallife cycle cost.• Job History—The suppliershould provide job references out-lining where the EIC has beenused. References should detail

location, type of structure protect-ed, and fire ratings specified.• Quality Programme—The sup-plier should have a certified ordocumented QA/QC system. • Supplier Financial Stability—Request annual reports or bankreferences from the supplier toverify financial stability.

When selecting an EIC, the pur-chaser should apply the criteriaabove in a rigorous analysis,because even though a product

falls within a generic classifica-tion, there can be major differ-ences in the formulations that willimpact on product performance(both fire and durability), applica-tion cost, and long-term mainte-nance costs.

An EIC for use on both offshoreand land-based structures requiresa product that has high impactstrength, flexibility, and goodadhesion. The flexibility gives sev-eral desirable properties, such asthe ability to relieve stresses gen-erated during rapid thermalcycling to prevent cracking anddisbonding. High impact strengthminimises damage from physicalcontact. The coating can with-stand the normal movementand/or vibrations found in steelsupport structures. It is perfectlysuited for coating and transport-ing the steel prior to erection fornew construction.

EIC find new uses due to theirunique physical properties. EICcan be moulded into complexshapes or into flat panels. Thesemoulded articles can be installedon site to eliminate the need tospray the coating. EIC are alsobeing used on overdecks to pro-vide fireproofing. Aggregate canbe added onto the EIC to provideanti-skid properties. Alternatively,anti-skid topcoats can be used toovercoat the EIC.

SummaryThis article reviews the recent

history of the evolution of firetesting methods to evaluate EICused to protect structural steelbeing used in petrochemical facil-ities today. The transition fromthe cellulosic fire conditions tothe more demanding hydrocarbonfire test and on to the develop-

Fig. 7: EIC provide fire protection to main support legs and to shell of flammable chemicalstorage tanks.

PCE December 1996Copyright ©1996, Technology Publishing Company 23

ment of a jet fire scenario is theresult of increased knowledge ofpossible fire events.

Safety and design specialists areusing sophisticated computertechniques to simulate a fireevent and to predict locations andtime of structural failure based onpredicted fire and explosionevents. This safety assessmentmethodology results in a morecost-effective approach to deter-mine where and how much EICmaterial is used.

The requirements for specifyingor selecting an EIC should bebased on an analysis of the instal-lation in question. Based on thepredicted fire and blast event, theEIC material must have demon-strated acceptable levels of actualfire performance conducted understandardised test conditionsaccompanied by the appropriatecertifications. The local environ-ment and climate should be con-sidered to determine if the EIChas the necessary physical and

chemical properties to providelong-term, maintenance-free per-formance. The product’s job his-tory should indicate if the appli-cation can be performed in thelocal climate and site conditionsfollowing the procedures thatwere used for test qualifications.

Suppliers of EIC are often askedby customers to help specify ormake recommendations on whatfire ratings should be met andwhere EIC should be used in theirfacilities. This presents problems:one is a possible conflict of inter-est (supplier - customer); secondis the question of whether thesupplier’s personnel have the nec-essary expertise to perform thesafety assessment; and third isthe possible liability issue if thefire and the safety assessmentwas incorrect.

Today, these safety assessmentsare being made based on predict-ed events that have to occur toproduce the fire or explosion.Because an accident is usually the

result of human error, is thereenough of a safety margin beingfigured into the assessment incase a particular accident scenariowas not considered? For someprojects the classic strugglebetween the interests of commer-cial and safety specialists arise.For this reason, and to ensureconsistency, the industry shouldlook to governmental or indepen-dent certifying authorities for afinal review of the safety assess-ment and proposed use of EICmaterials for each project.

References1. Brian Songhurst, “OffshorePlatform Design Safety and Cost,”Expro 1992, p. 113.2. John Spouge, “Assessment ofMajor Offshore Hazards,” Expro1992, p. 171.3. Dr. Colin Billington, “StructuralCost Savings,” Expro 1992, p. 117.4. Ash Bakshi, “Alliance ChangesEconomics of Andrew FieldDevelopment,” Offshore, January1995, p. 30.5. C.P. Rogers and M. Ramsden,“Optimisation of Passive FireProtection for Offshore StructuresUsing Progressive CollapseTechniques,” paper presented atERA Conference on OffshoreStructural Design Hazards, Safetyand Engineering, London, 15-16November 1994.6. J.H. Warren and A.A. Corona,“This Method Tests Fire ProtectiveCoatings,” HydrocarbonProcessing, January 1975.7. Offshore Technology Report -OTI 95 634, “Jet-Fire ResistanceTest of Passive Fire ProtectionMaterials,” Health and SafetyExecutive, 1996.

Fig. 8: Crew quarters and helideck being lifted onto main deck. EIC must posses adhesion,flexibility, and impact resistance to prevent material damage.