Static Ignition Concerns in Static Ignition Concerns in Aboveground Petroleum Storage Aboveground Petroleum Storage

TanksTanks

Guy R. Colonna, PEGuy R. Colonna, PENTEPSNTEPS

Ft. Worth, TXFt. Worth, TXJanuary 22, 2009January 22, 2009

OverviewOverview

• Hazard RecognitionHazard Recognition– Industry experiencesIndustry experiences

•Barton Solvents, Kansas – CSB investigationBarton Solvents, Kansas – CSB investigation

– What is static electricity?What is static electricity?

• Hazard EvaluationHazard Evaluation– Static accumulating liquidsStatic accumulating liquids

• Hazard ControlHazard Control– Four stepsFour steps– API 2003, ISGOTT, NFPA 77API 2003, ISGOTT, NFPA 77

Barton Solvents – Valley Barton Solvents – Valley Center, KSCenter, KS

• Date: July 17, 2007Date: July 17, 2007

• Product: VM & P NaphthaProduct: VM & P Naphtha

• Operation:Operation:– Transfer naphtha from tanker truck to Transfer naphtha from tanker truck to

15,000 gallon aboveground storage tank15,000 gallon aboveground storage tank

• Incident: explosion and fireIncident: explosion and fire– Destroyed tank farm – tank blown 130 ft.Destroyed tank farm – tank blown 130 ft.– Evacuate 6000 residentsEvacuate 6000 residents

Barton Solvents – FireBarton Solvents – Fire

CSB VideoCSB Video

http://www.csb.gov/index.cfm?folder=completed_investigations&page=info&INV_ID=73

Barton Solvents – Explosion Barton Solvents – Explosion

Level Float – showing Level Float – showing linkagelinkage

Varnish Makers’ & Painters’ Varnish Makers’ & Painters’ (VM & P) Naphtha Properties(VM & P) Naphtha Properties

• Flash Point – 58°F (14°C) as tested Flash Point – 58°F (14°C) as tested by CSBby CSB– NFPA Fire Protection Guide to Hazardous NFPA Fire Protection Guide to Hazardous

Materials lists 28°F, 50°F and 85°FMaterials lists 28°F, 50°F and 85°F– NFPA 30 Classification – IB (IC)NFPA 30 Classification – IB (IC)

• Flammable Range – 0.9 - 6.7%Flammable Range – 0.9 - 6.7%

• Conductivity – 3 pS/m (per CSB tests)Conductivity – 3 pS/m (per CSB tests)– Less than 100 pS/m generally Less than 100 pS/m generally

considered nonconductive considered nonconductive

CSB Key FindingsCSB Key Findings

• Ignitable vapor-air mixture in head Ignitable vapor-air mixture in head spacespace

• Stop-start filling introduced air in the Stop-start filling introduced air in the transfer piping agitating sediment transfer piping agitating sediment and water – bubbling effectand water – bubbling effect

• Liquid level gauging system float Liquid level gauging system float with loose linkage provided gap for with loose linkage provided gap for potential sparkpotential spark

• MSDS for VM&P naphtha inadequateMSDS for VM&P naphtha inadequate

CSB Recommendations – CSB Recommendations – nonconductive flammable nonconductive flammable liquidsliquids• Request additional manufacturer Request additional manufacturer

guidanceguidance

• Add an inert gas to tank head spaceAdd an inert gas to tank head space

• Modify or replace loose linkage tank Modify or replace loose linkage tank level floatslevel floats

• Add an anti-static agentAdd an anti-static agent

• Reduce flow (pumping) velocityReduce flow (pumping) velocity– Recommend less than 1 m/sec (Barton Recommend less than 1 m/sec (Barton

was 4.6 m/sec)was 4.6 m/sec)

CSB Recommendation – CSB Recommendation – request additional request additional manufacturer guidancemanufacturer guidance• CSB reported MSDSs do not provide CSB reported MSDSs do not provide

adequate information regarding adequate information regarding hazardshazards– Determine whether flammable liquid is Determine whether flammable liquid is

nonconductive (static accumulator)nonconductive (static accumulator)– Determine whether flammable liquid is Determine whether flammable liquid is

capable of producing ignitable vapor-air capable of producing ignitable vapor-air mixture inside a storage tankmixture inside a storage tank•Flash point, vapor pressure, flammable range, Flash point, vapor pressure, flammable range,

minimum ignition energy (MIE)minimum ignition energy (MIE)

Liquid ConductivityLiquid Conductivity

• Non-conductive – static accumulatorsNon-conductive – static accumulators– Conductivities less than 50 pS/mConductivities less than 50 pS/m– Relaxation times greater than 0.36 secondsRelaxation times greater than 0.36 seconds

• Semi-conductive – static non-accumulatorsSemi-conductive – static non-accumulators– Conductivities between 50 pS/m and 10Conductivities between 50 pS/m and 1044 pS/m pS/m– Relaxation times between 0.002 and 0.36 secRelaxation times between 0.002 and 0.36 sec

• Conductive – greater than 10Conductive – greater than 1044 pS/m and pS/m and less than 0.002 sec relaxation timeless than 0.002 sec relaxation time

Static Accumulating LiquidsStatic Accumulating Liquids

• VM&P NaphthaVM&P Naphtha

• CyclohexaneCyclohexane

• n-Heptanen-Heptane

• BenzeneBenzene

• TolueneToluene

• n-Hexanen-Hexane

• XyleneXylene

• Ethyl BenzeneEthyl Benzene

• StyreneStyrene

• Jet fuelsJet fuels

• KerosenesKerosenes

CSB Recommendation – CSB Recommendation – inert tank head spaceinert tank head space• Eliminate ignitable vapor-air mixtureEliminate ignitable vapor-air mixture

– Add nonflammable, nonreactive (inert) Add nonflammable, nonreactive (inert) gasgas

– Nitrogen, carbon dioxide, argonNitrogen, carbon dioxide, argon•Consider properties of inert gasesConsider properties of inert gases

•Carbon dioxide as a gas, generates staticCarbon dioxide as a gas, generates static

– Limiting oxidant concentration (LOC)Limiting oxidant concentration (LOC)•Refer to NFPA 69 for guidance on valuesRefer to NFPA 69 for guidance on values

– Caution when opening inerted tanks for Caution when opening inerted tanks for inspection – oxygen levels will be IDLHinspection – oxygen levels will be IDLH

CSB Recommendation – CSB Recommendation – modify tank level floatmodify tank level float

• Inert tank head spaceInert tank head space

• Inspect and replace as necessary Inspect and replace as necessary floats with device that does not cause floats with device that does not cause sparkssparks

• Modify floats – bonded and groundedModify floats – bonded and grounded

• Reduce liquid flow velocityReduce liquid flow velocity

• Remove slack in the tape connected to Remove slack in the tape connected to the floatthe float

NFPA 77 - GaugingNFPA 77 - Gauging

• Where possible, gauging should be Where possible, gauging should be carried out using automatic gauging carried out using automatic gauging systemssystems

• Gauge floats and similar devices should Gauge floats and similar devices should be electrically bonded to the tank shell be electrically bonded to the tank shell through a conductive lead-in tape or through a conductive lead-in tape or conductive guide wiresconductive guide wires

• Free-floating, unbonded floats can be Free-floating, unbonded floats can be effective spark promoters and should be effective spark promoters and should be avoidedavoided

Static Electricity BasicsStatic Electricity Basics

• Charge must be generated by Charge must be generated by separation of surfacesseparation of surfaces

• Charge must be collected and Charge must be collected and accumulatedaccumulated

• Charge dischargeCharge discharge– Sufficient charge to jump the gap and Sufficient charge to jump the gap and

produce an incendive sparkproduce an incendive spark

• Flammable concentration within the Flammable concentration within the gapgap

Charge SeparationCharge Separation

• Flow of liquids through pipes or filtersFlow of liquids through pipes or filters

• Settling of a solid or immiscible liquid Settling of a solid or immiscible liquid through a liquidthrough a liquid

• Ejection of particles or droplets from Ejection of particles or droplets from a nozzlea nozzle

• Splashing or agitation of a liquid Splashing or agitation of a liquid against a solid surfaceagainst a solid surface

• Vigorous rubbing together and Vigorous rubbing together and separation of synthetic polymersseparation of synthetic polymers

Electrostatic DischargeElectrostatic Discharge

• Conductor to conductor – produces Conductor to conductor – produces sparkspark

• Conductor to non-conductorConductor to non-conductor– Characterized as corona discharge or Characterized as corona discharge or

brush dischargebrush discharge– Generally not associated with a sparkGenerally not associated with a spark– Generally not incendiveGenerally not incendive

Electrostatic DischargeElectrostatic Discharge

• Dependent upon strength of field between Dependent upon strength of field between points of discharge (voltage difference)points of discharge (voltage difference)

• Field strength near protrusions – greatest Field strength near protrusions – greatest – Single electrode discharges – rarely incendiveSingle electrode discharges – rarely incendive

• Two electrode dischargesTwo electrode discharges– Sampling device and liquid surfaceSampling device and liquid surface– Ungrounded object floating on surfaceUngrounded object floating on surface– Ungrounded equipment suspended in tankUngrounded equipment suspended in tank

Summary - precautionsSummary - precautions

• Eliminate flammable vapor-air mixtureEliminate flammable vapor-air mixture– Ventilate to less than 25% LFL or inertVentilate to less than 25% LFL or inert

• Control transfer flow rateControl transfer flow rate

• Identify properties of productsIdentify properties of products

• Bond or ground sampling or gauging Bond or ground sampling or gauging devices – fixed or portabledevices – fixed or portable

• Allow relaxation timeAllow relaxation time

• Add anti-static agentAdd anti-static agent

Any Questions?Any Questions?

gcolonna@nfpa.org