1、Designation: D 4865 98 (Reapproved 2003)e1An American National StandardStandard Guide forGeneration and Dissipation of Static Electricity in PetroleumFuel Systems1This standard is issued under the fixed designation D 4865; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEWarning notes were editorially moved into the standard text in August 2
3、003.INTRODUCTIONEvery year a number of fires and explosions in petroleum product systems are attributed to sparkignition from accumulated static electricity. Such fires require a flammable hydrocarbon/air mixtureand an ignition source. Safety practices can concentrate on the elimination of either fa
4、ctor, but thisguide provides a general background on how electrostatic charges are formed and how they may beprevented or dissipated.A subtle and often misunderstood feature of these incidents is the possible accumulation ofhazardous electrostatic charges in systems which are properly bonded and gro
5、unded. This can occurbecause refined hydrocarbon fuels have low electrical conductivities and electrostatic charges may beretained within the fuel and on its surfaces.1. Scope1.1 This guide describes how static electricity may begenerated in petroleum fuel systems, the types of equipmentconducive to
6、 charge generation, and methods for the safedissipation of such charges. This guide is intended to increaseawareness of potential operating problems and hazards result-ing from electrostatic charge accumulation.1.2 This guide is not intended to provide specific solutionsbut indicates available techn
7、iques the user may wish toinvestigate to alleviate electrostatic charges. This guide doesnot cover the effects of stray currents or of lightning, either ofwhich can also produce sparks leading to fires or explosions.1.3 This guide is not intended to address detailed safetypractices associated with s
8、tatic electricity in petroleum productsystems.1.4 The values in SI units are to be regarded as the standard.The values in parentheses are for information only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user
9、 of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 56 Test Method for Flash Point by Tag Closed Tester2D 93 Test Methods for Flash Point by Pensky-MartensClosed Cu
10、p Tester2D 323 Test Method for Vapor Pressure of Petroleum Prod-ucts (Reid Method)2D 396 Specification for Fuel Oils2D 910 Specification for Aviation Gasolines2D 975 Specification for Diesel Fuel Oils2D 1655 Specification for Aviation Turbine Fuels2D 2276 Test Method for Particulate Contaminant in A
11、via-tion Fuel by Line Sampling2D 2624 Test Methods for Electrical Conductivity of Avia-tion and Distillate Fuels2D 2880 Specification for Gas Turbine Fuel Oils2D 3699 Specification for Kerosine3D 3948 Test Methods for Determining Water SeparationCharacteristics of Aviation Turbine Fuels by PortableS
12、eparometer3D 4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace Contamination3D 4308 Test Method for Electrical Conductivity of LiquidHydrocarbons by Precision Meter31This guide is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the d
13、irect responsibility of Subcommittee D02.J0 onAviation Fuels.Current edition approved June 10, 2003. Published August 2003. Originallyapproved in 1988. Last previous edition approved in 1998 as D 486598.2Annual Book of ASTM Standards, Vol 05.01.3Annual Book of ASTM Standards, Vol 05.02.1Copyright AS
14、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 5191 Test Method for Vapor Pressure of Petroleum Prod-ucts (Mini Method)3D 5452 Test Method for Particulate Contamination in Avia-tion Fuels by Laboratory Filtration42.2 National Fire Protection A
15、ssociation (NFPA) Stan-dards:5NFPA Standard No. 30 Flammable and Combustible LiquidCodeNFPA Standard No. 407 Standard on Aircraft Fuel Servicing2.3 Canadian General Standard Board (CGSB) Specifica-tion:6CAN/CGSB 3.6 Regular Sulphur Diesel FuelCAN/CGSB 3.517 Automotive Low Sulphur Diesel Fuel2.4 Brit
16、ish Standards Institute (BSI) Standard:BS 5958 (Part 2) Recommendations for Particular IndustrialSituations73. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 bonding, vthe practice of providing electrical con-nections between conductive parts of a fuel system to precludevoltage
17、differences between the parts.3.1.2 bottom loading, vthe practice of filling transportcompartments by pumping fuel through a bottom inlet.3.1.3 charge accumulation, nthe increase of electrostaticcharges in a tank, compartment, or liquid resulting from a ratedissipation slower than the rate of charge
18、 delivery by theincoming product.3.1.4 charge generation, vthe creation of electrostaticcharges in a liquid due to the separation of ionic species duringliquid flow.3.1.5 charge relaxation, nthe decrease of electrostaticcharges with time.3.1.6 combustible liquid, na liquid having a flash point ator
19、above 38C (100F) (See Test Methods D 56 and D 93).3.1.6.1 DiscussionSubdivisions of this classification willbe found in NFPA Standard No. 30.3.1.7 conductivity, nthe reciprocal of electrical resistivity,the capability to transmit electrostatic charges normally ex-pressed in picoSiemens per metre (pS
20、/m) for petroleum prod-ucts.3.1.7.1 DiscussionConductivity has also been expressedin conductivity units (C.U.) where I.C.U. = 1 pS/m = 1 3 1012 V1m1.3.1.8 conductivity improver additive, n a material addedto a fuel in very small amounts to increase its electricalconductivity and thereby reduce relax
21、ation time.3.1.8.1 DiscussionConductivity improver additives arealso known as static dissipator additives (SDAs) or antistaticadditives.3.1.9 flammable liquid, na liquid having a flash pointbelow 38C (100F) (see Test Methods D 56 and D 93) andhaving vapor pressure (Test Method D 323 or D 5191) notex
22、ceeding 276 kPa (40 psia) (see NFPA Standard No. 30).3.1.9.1 DiscussionThe definition of flammable is cur-rently under discussion by the UN Committee of Experts on theTransportation of Dangerous Goods.3.1.10 grounding, vthe practice of providing electricalcontinuity between a fuel handling system an
23、d ground or earth.3.1.11 high vapor pressure product, na product having avapor pressure above 31 kPa (4.5 psia) (1).83.1.12 intermediate vapor pressure product, na productwith a vapor pressure below 31 kPa (4.5 psia) and a flash pointbelow 38C (100F) (1).3.1.13 low vapor pressure product, na product
24、 with aflash point above 38C (100F) (1).3.1.14 relaxation time, nthe time required for a charge todissipate to 36.8 % of the original value (2).3.1.15 residence time, nthe length of time after a charge isgenerated that a product remains in piping or a closed vessel.3.1.16 splash filling, vthe practi
25、ce of allowing fuel tofree-fall or to impinge at high velocity on a tank wall whileloading a compartment.3.1.17 static discharge, vthe release of electrical energyin the form of a spark or corona discharge across a gap betweensurfaces of differing voltage.3.1.18 switch loading, vthe practice of load
26、ing one typeof product into a tank or compartment which previouslycontained a different type of product.3.1.18.1 DiscussionWhen involving handling safety,switch loading often refers to loading a low vapor pressureproduct into a tank or compartment previously containing ahigh vapor pressure product.
27、A flammable vapor in the ullagespace is likely to result.3.1.19 top loading, vthe practice of filling transport com-partments through an open dome at the top of the transport.3.1.20 ullage (vapor) space, nthe space between theliquid surface and the top of the tank or compartment contain-ing the liqu
28、id.3.1.21 unbonded charge collector or accumulator,nunbonded, conductive objects which concentrate electricalcharges.3.1.21.1 DiscussionThese unbonded charge collectorsmay be objects floating on the surface of the charged liquid orobjects such as gaging tapes lowered toward the chargedsurface. The h
29、igh conductivity of metallic charge collectorspermits the rapid discharge of accumulated charges.4. Significance and Use4.1 Pumping, filtering, and tank filling of petroleum prod-ucts, particularly refined distillates, can cause the generationand accumulation of electrostatic charges and can result
30、instatic discharges capable of causing fires and explosions. Thisguide provides an overview of the factors involved in thegeneration of such electrostatic charges. Methods are describedfor the alleviation of the problem, and cited authoritativereferences contain more details.4Annual Book of ASTM Sta
31、ndards, Vol 05.03.5Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02269-9101.6Available from Canadian General Standard Board, Ottawa, Canada.7Part 2 of British Standard Code of Practice for Control of Undesirable StaticElectricity, available from British S
32、tandards Institute, 2 Park St., London, EnglandWIA2B5.8The boldface numbers in parentheses refer to the references at the end of thisstandard.D 4865 98 (2003)e124.2 This guide is not intended to provide operating or safetyrules for the handling of petroleum products to avoid electro-static hazards.5
33、. Background5.1 Ignition Principles:5.1.1 For ignition to occur, it is necessary to have an ignitionsource of sufficient energy and a mixture of fuel and air in theflammable range. The boundaries of the flammable range aredefined by the lean and rich limits. Below the lean limit thereis not enough h
34、ydrocarbon vapor to sustain combustion,whereas above the rich limit there is not enough oxygen. Themixture temperature and pressure and the fuel characteristics,including boiling range and vapor pressure, determine theamount of a given fuel which is vaporized and thereforeestablish the flammability
35、of the mixture. Normally these limitsare measured under equilibrium conditions with the fuelpartially or completely vaporized. However, ignitions haveoccurred below the lean ignition limit when the fuel was in theform of a foam or spray. Also, systems are not normally inequilibrium when there is suf
36、ficient fuel flow to generateelectrostatic charges. Turbulence in the vapor space can lead tounexpected flammable air-vapor mixtures in localized areas.Equilibrium flammability limits can therefore be used only asrough guidelines of flammability.5.1.2 The second requirement for ignition is a static
37、dis-charge of sufficient energy and duration. Discharges occurwhen the voltage across a gap exceeds the breakdown strengthof the fluid or air in the gap. Minimum energy requirementsvary widely depending on the nature of the spark, the configu-ration of the spark gap and electrodes, nature of materia
38、ls, andother factors. There is no doubt that sparks due to staticelectricity in petroleum systems can have sufficient energy toignite flammable mixtures when they occur in the vapor space.Discharges from highly charged fluids are known to penetrateplastic tubing.5.2 Charge GenerationWhenever a hydro
39、carbon liquidflows with respect to another surface, a charge is generated inthe liquid and an equal but opposite charge is imposed on thatsurface. This charge is attributed to ionic impurities present inparts per million or parts per billion quantities. At rest theimpurities are adsorbed at the inte
40、rface between the fuel andthe container walls, with one part of the ionic material havinga strong attachment for the fuel or the container. Under theseconditions, there is no net charge on the fuel. However, whenthe fuel flows, one set of charges is swept along with the fuelwhile the opposite charge
41、s which accumulate along the wallsurfaces usually leak to ground. This charge separation resultsin a rise in voltage in the moving fuel.5.3 Charge RelaxationWhen charged fuel enters a tank, asubstantial voltage difference may be produced between thesurface of the liquid and the tank walls and this m
42、ay result ina static discharge. The voltage difference is limited by chargedissipation/relaxation processes which occur both in the pipe-work downstream of strong charge generating elements and inthe tank itself. Relaxation in the pipework reduces the amountof charge that reaches the tank while rela
43、xation in the tankreduces the voltage produced by a given amount of inletcharge. Under most practical loading conditions, the voltagegenerated by a given inlet charge density is proportional to therelaxation time of the fuel. This relaxation time is inverselyproportional to the conductivity and is a
44、pproximately 20 swhen the conductivity is 1 pS/m. The conductivity of hydro-carbon fuels is highly variable as a result of natural productdifferences, commingling, or the use of additives. Products notcontaining additives, including diesel fuels, may have conduc-tivities of less than 1 pS/m but many
45、 modern additive packages(not just static dissipator additives) provide considerably in-creased conductivity, possibly up to several hundred pS/m ormore. The relaxation time can therefore be anything form afraction of a second to a number of minutes. It has been foundthat the reduced relaxation time
46、 produced by increasing theconductivity more than compensates for any increase in chargegeneration that may occur. The highest voltages and electro-static ignition risks are therefore associated with low conduc-tivities. Unless conductivities are controlled, the possibility ofencountering low conduc
47、tivity product should be allowed forwhen defining safe loading procedures (3, 4).6. Practical Problems6.1 Certain switch loading operations, such as loading ofdiesel fuel into a truck which previously carried gasoline andstill contains vapors or liquid gasoline, are especially danger-ous. The combin
48、ation of a flammable vapor space and chargeddiesel fuel presents a potential explosion hazard if an electro-static discharge occurs. Analyses (5) of past tank truck acci-dents reveal that switch loading or splash filling, or both,account for 80 % of static-initiated explosions. More informa-tion on
49、the hazards of flammable atmospheres formed duringswitch loading will be found in 7.6.6.2 Microfilters and filter-separators are prolific generatorsof electrostatic charges. The type of ionic impurity in theproduct as well as the type of surface determine the magnitudeand polarity of separated charges that are swept away in theflowing stream. Many additives in fuel increase the level ofcharge generation upon filtration, although in the case of staticdissipator additives this is more than compensated by enhancedcharge dissipation. Most common filt
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