1、Designation: D4865 09 (Reapproved 2014) An American National StandardStandard Guide forGeneration and Dissipation of Static Electricity in PetroleumFuel Systems1This standard is issued under the fixed designation D4865; the number immediately following the designation indicates the year oforiginal a
2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONEvery year a number of fires and explosions in petroleum product syst
3、ems 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 factor, but thisguide provides a general background on how electrostatic charges are fo
4、rmed 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 grounded. This can occurbecause refined hydrocarbon fuels have low electrical conductivi
5、ties 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 charge generation, and methods for the safedissipation of such charges. This guide i
6、s 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 techniques the user may wish toinvestigate to alleviate electrostatic charges. This guide
7、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 static electricity in petroleum productsystems.1.4 The values in SI units are to be re
8、garded 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 of this standard to establish appro-priate safety and health practices and determine
9、 the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D56 Test Method for Flash Point by Tag Closed Cup TesterD93 Test Methods for Flash Point by Pensky-MartensClosed Cup TesterD323 Test Method for Vapor Pressure of Petroleum Products(Reid Method)D396
10、Specification for Fuel OilsD910 Specification for Leaded Aviation GasolinesD975 Specification for Diesel Fuel OilsD1655 Specification for Aviation Turbine FuelsD2276 Test Method for Particulate Contaminant in AviationFuel by Line SamplingD2624 Test Methods for Electrical Conductivity of Aviationand
11、Distillate FuelsD2880 Specification for Gas Turbine Fuel OilsD3699 Specification for KerosineD3948 Test Method for Determining Water Separation Char-acteristics ofAviationTurbine Fuels by Portable Separom-eterD4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace Contamination
12、D4308 Test Method for Electrical Conductivity of LiquidHydrocarbons by Precision MeterD5191 Test Method for Vapor Pressure of Petroleum Prod-ucts (Mini Method)1This guide is under the jurisdiction of ASTM Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibili
13、ty of Subcom-mittee D02.J0.04 on Additives and Electrical Properties.Current edition approved Oct. 1, 2014. Published November 2014. Originallyapproved in 1988. Last previous edition approved in 2009 as D4865 09. DOI:10.1520/D4865-09R14.2For referenced ASTM standards, visit the ASTM website, www.ast
14、m.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D5452 Test
15、 Method for Particulate Contamination in Avia-tion Fuels by Laboratory FiltrationD6615 Specification for Jet B Wide-Cut Aviation TurbineFuel2.2 National Fire Protection Association (NFPA) Stan-dards:3NFPA Standard No. 30 Flammable and Combustible LiquidCodeNFPAStandard No. 407 Standard onAircraft Fu
16、el Servicing2.3 Canadian General Standard Board (CGSB) Specifica-tion:4CAN/CGSB 3.6 Regular Sulphur Diesel FuelCAN/CGSB 3.517 Automotive Low Sulphur Diesel Fuel2.4 British Standards Institute (BSI) Standard:BS 5958 (Part 2) Recommendations for Particular IndustrialSituations53. Terminology3.1 Defini
17、tions 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 differences between the parts.3.1.2 bottom loading, vthe practice of filling transportcompartments by pumping fuel through a bottom
18、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 delivery by theincoming product.3.1.4 charge generation, vthe creation of electrostaticcharges in a liquid due to the separation of
19、 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 above 38C (100F) (See Test Methods D56 and D93).3.1.6.1 DiscussionSubdivisions of this classification willbe found in NFPA Standard
20、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/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
21、10121m1.3.1.8 conductivity improver additive, n a material addedto a fuel in very small amounts to increase its electricalconductivity and thereby reduce relaxation time.3.1.8.1 DiscussionConductivity improver additives arealso known as static dissipator additives (SDAs) or antistaticadditives.3.1.9
22、 flammable liquid, na liquid having a flash pointbelow 38C (100F) (see Test Methods D56 and D93) andhaving vapor pressure (Test Method D323 or D5191) notexceeding 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 Commi
23、ttee of Experts on theTransportation of Dangerous Goods.3.1.10 grounding, vthe practice of providing electricalcontinuity between a fuel handling system and ground or earth.3.1.11 high vapor pressure product, na product having avapor pressure above 31 kPa (4.5 psia) (1).63.1.12 intermediate vapor pr
24、essure 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 with a flashpoint 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
25、.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 practice 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
26、 electrical energy inthe form of a spark or corona discharge across a gap betweensurfaces of differing voltage.3.1.18 switch loading, vthe practice of loading one type ofproduct into a tank or compartment which previously containeda different type of product.3.1.18.1 DiscussionWhen involving handlin
27、g safety,switch loading often refers to loading a low vapor pressureproduct into a tank or compartment previously containing ahigh vapor pressure product. 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 dom
28、e 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 liquid.3.1.21 unbonded charge collector or accumulator,nunbonded, conductive objects which concentrate electricalcharges.3.1.21.1 DiscussionThese unb
29、onded charge collectorsmay be objects floating on the surface of the charged liquid orobjects such as gaging tapes lowered toward the chargedsurface. The high conductivity of metallic charge collectorspermits the rapid discharge of accumulated charges.4. Significance and Use4.1 Pumping, filtering, a
30、nd tank filling of petroleumproducts, particularly refined distillates, can cause the genera-tion and accumulation of electrostatic charges and can result in3Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02269-9101.4Available from Canadian General Standar
31、d Board, Ottawa, Canada.5Part 2 of British Standard Code of Practice for Control of Undesirable StaticElectricity, available from British Standards Institute, 2 Park St., London, EnglandWIA2B5.6The boldface numbers in parentheses refer to the references at the end of thisstandard.D4865 09 (2014)2sta
32、tic 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.4.2 This guide is not intende
33、d to provide operating or safetyrules for the handling of petroleum products to avoid electro-static hazards.5. 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 bound
34、aries of the flammable range aredefined by the lean and rich limits. Below the lean limit thereis not enough hydrocarbon 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 v
35、apor pressure, determine theamount of a given fuel which is vaporized and thereforeestablish the flammability of the mixture. Normally these limitsare measured under equilibrium conditions with the fuelpartially or completely vaporized. However, ignitions haveoccurred below the lean ignition limit w
36、hen the fuel was in theform of a foam or spray. Also, systems are not normally inequilibrium when there is sufficient fuel flow to generateelectrostatic charges. Turbulence in the vapor space can lead tounexpected flammable air-vapor mixtures in localized areas.Equilibrium flammability limits can th
37、erefore be used only asrough guidelines of flammability.5.1.2 The second requirement for ignition is a static 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 wide
38、ly depending on the nature of the spark, the configu-ration of the spark gap and electrodes, nature of materials, 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.Di
39、scharges from highly charged fluids are known to penetrateplastic tubing.5.2 Charge GenerationWhenever a hydrocarbon 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 impuriti
40、es present inparts per million or parts per billion quantities. At rest theimpurities are adsorbed at the interface 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 t
41、he fuel. However, whenthe fuel flows, one set of charges is swept along with the fuelwhile the opposite charges 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,
42、asubstantial voltage difference may be produced between thesurface of the liquid and the tank walls and this may 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
43、and inthe tank itself. Relaxation in the pipework reduces the amountof charge that reaches the tank while relaxation 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
44、 to therelaxation time of the fuel. This relaxation time is inverselyproportional to the conductivity and is approximately 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. P
45、roducts notcontaining additives, including diesel fuels, may have conduc-tivities of less than 1 pS/m but many 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
46、 anything form afraction of a second to a number of minutes. It has been foundthat the reduced relaxation time 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 associ
47、ated with low conduc-tivities. Unless conductivities are controlled, the possibility ofencountering low conductivity 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
48、previously carried gasoline andstill contains vapors or liquid gasoline, are especially danger-ous. The combination 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 sw
49、itch loading or splash filling, or both,account for 80 % of static-initiated explosions. More informa-tion on 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 t
