1、Designation: D4865 09An 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 adoption or, in the
2、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 systems are attributed
3、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 formed and how they m
4、ay 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 conductivities and electrosta
5、tic 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 is intended to incre
6、aseawareness 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 doesnot cover the e
7、ffects 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 regarded as the stand
8、ard.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 the applica-bility
9、 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 Prod-ucts (Reid Method)D396 Specification for
10、 Fuel OilsD910 Specification for Aviation GasolinesD975 Specification for Diesel Fuel OilsD1655 Specification for Aviation Turbine FuelsD2276 Test Method for Particulate Contaminant inAviationFuel by Line SamplingD2624 Test Methods for Electrical Conductivity ofAviationand Distillate FuelsD2880 Spec
11、ification for Gas Turbine Fuel OilsD3699 Specification for KerosineD3948 Test Method for Determining Water SeparationCharacteristics of Aviation Turbine Fuels by PortableSeparometerD4306 Practice for Aviation Fuel Sample Containers forTests Affected by Trace ContaminationD4308 Test Method for Electr
12、ical Conductivity of LiquidHydrocarbons by Precision Meter1This guide is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.J0.04on Additives and Electrical Properties.Current edition approved Aug. 1, 2009. Published
13、November 2009. Originallyapproved in 1988. Last previous edition approved in 2003 as D486598 (2003)1.DOI: 10.1520/D4865-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, re
14、fer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D5191 Test Method for Vapor Pressure of Petroleum Prod-ucts (Mini Method)D5452 Test Method for Particulate Contamination in
15、 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 Fuel Servicing2.3 Canadian General Standar
16、d 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 Definitions of Terms Specific to This Standard
17、: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 inlet.3.1.3 charge accumulation, nthe in
18、crease 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 ionic species duringliquid flow.3.1.5 c
19、harge 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 No. 30.3.1.7 conductivity, nthe reciproc
20、al 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 3 1012 V1m1.3.1.8 conductivity improv
21、er 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 flammable liquid, na liquid havi
22、ng 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 Committee of Experts on theTransportat
23、ion 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 pressure product, na productwith a
24、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 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
25、 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 electrical energyin the form of
26、a spark or corona discharge across a gap betweensurfaces of differing voltage.3.1.18 switch loading, vthe practice of loading 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 ref
27、ers 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 dome at the top of the transport.3.1
28、.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 unbonded charge collectorsmay be obj
29、ects 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, and tank filling of petroleum prod
30、-ucts, particularly refined distillates, can cause the generationand accumulation of electrostatic charges and can result instatic discharges capable of causing fires and explosions. Thisguide provides an overview of the factors involved in thegeneration of such electrostatic charges. Methods are de
31、scribed3Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02269-9101.4Available from Canadian General Standard Board, Ottawa, Canada.5Part 2 of British Standard Code of Practice for Control of Undesirable StaticElectricity, available from British Standards In
32、stitute, 2 Park St., London, EnglandWIA2B5.6The boldface numbers in parentheses refer to the references at the end of thisstandard.D4865 092for the alleviation of the problem, and cited authoritativereferences contain more details.4.2 This guide is not intended to provide operating or safetyrules fo
33、r 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 boundaries of the flammable range aredefined
34、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 vapor pressure, determine theamount of a
35、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 when the fuel was in theform of a foam or
36、 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 therefore be used only asrough guidelines
37、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 widely depending on the nature of the spark,
38、 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.Discharges from highly charged fluids are
39、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 impurities present inparts per million or parts
40、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 the fuel. However, whenthe fuel flows, on
41、e 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, asubstantial voltage difference may be p
42、roduced 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 and inthe tank itself. Relaxation in the
43、 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 to therelaxation time of the fuel. This
44、 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. Products notcontaining additives, includi
45、ng 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 anything form afraction of a second to
46、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 associated with low conduc-tivities. Unless co
47、nductivities 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 previously carried gasoline andstill con
48、tains 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 switch loading or splash filling, or both,
49、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 the case of staticdissipator additives this
