ASTM D4865-98(2003)e1
(Guide)Standard Guide for Generation and Dissipation of Static Electricity in Petroleum Fuel Systems
Standard Guide for Generation and Dissipation of Static Electricity in Petroleum Fuel Systems
SIGNIFICANCE AND USE
Pumping, filtering, and tank filling of petroleum products, particularly refined distillates, can cause the generation and accumulation of electrostatic charges and can result in static discharges capable of causing fires and explosions. This guide provides an overview of the factors involved in the generation of such electrostatic charges. Methods are described for the alleviation of the problem, and cited authoritative references contain more details.
This guide is not intended to provide operating or safety rules for the handling of petroleum products to avoid electrostatic hazards.
SCOPE
1.1 This guide describes how static electricity may be generated in petroleum fuel systems, the types of equipment conducive to charge generation and methods for the safe dissipation of such charges. The guide is intended to increase awareness of potential operating problems and hazards resulting from electrostatic charge accumulation.
1.2 This guide is not intended to provide specific solutions but indicates available techniques the user may wish to investigate to alleviate electrostatic charges. The guide does not cover the effects of stray currents or of lightning, either of which can also produce sparks leading to fires or explosions.
1.3 This guide is not intended to address detailed safety practices associated with static electricity in petroleum product systems.
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 the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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An American National Standard
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Designation:D4865–98 (Reapproved 2003)
Standard Guide for
Generation and Dissipation of Static Electricity in Petroleum
Fuel Systems
This standard is issued under the fixed designation D4865; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Warning notes were editorially moved into the standard text in August 2003.
INTRODUCTION
Every year a number of fires and explosions in petroleum product systems are attributed to spark
ignition from accumulated static electricity. Such fires require a flammable hydrocarbon/air mixture
and an ignition source. Safety practices can concentrate on the elimination of either factor, but this
guide provides a general background on how electrostatic charges are formed and how they may be
prevented or dissipated.
A subtle and often misunderstood feature of these incidents is the possible accumulation of
hazardous electrostatic charges in systems which are properly bonded and grounded. This can occur
because refined hydrocarbon fuels have low electrical conductivities and electrostatic charges may be
retained within the fuel and on its surfaces.
1. Scope 2. Referenced Documents
1.1 This guide describes how static electricity may be 2.1 ASTM Standards:
generated in petroleum fuel systems, the types of equipment D56 Test Method for Flash Point byTag Closed CupTester
conducive to charge generation, and methods for the safe
dissipation of such charges. This guide is intended to increase D93 Test Methods for Flash Point by Pensky-Martens
awareness of potential operating problems and hazards result- Closed Cup Tester
ing from electrostatic charge accumulation. D323 Test Method for Vapor Pressure of Petroleum Prod-
1.2 This guide is not intended to provide specific solutions ucts (Reid Method)
but indicates available techniques the user may wish to D396 Specification for Fuel Oils
investigate to alleviate electrostatic charges. This guide does D910 Specification for Aviation Gasolines
not cover the effects of stray currents or of lightning, either of D975 Specification for Diesel Fuel Oils
which can also produce sparks leading to fires or explosions. D1655 Specification for Aviation Turbine Fuels
1.3 This guide is not intended to address detailed safety D2276 TestMethodforParticulateContaminantinAviation
practicesassociatedwithstaticelectricityinpetroleumproduct Fuel by Line Sampling
systems. D2624 TestMethodsforElectricalConductivityofAviation
1.4 ThevaluesinSIunitsaretoberegardedasthestandard. and Distillate Fuels
The values in parentheses are for information only. D2880 Specification for Gas Turbine Fuel Oils
1.5 This standard does not purport to address all of the D3699 Specification for Kerosine
safety concerns, if any, associated with its use. It is the D3948 Test Method for Determining Water Separation
responsibility of the user of this standard to establish appro- Characteristics of Aviation Turbine Fuels by Portable
priate safety and health practices and determine the applica- Separometer
bility of regulatory limitations prior to use. D4306 Practice for Aviation Fuel Sample Containers for
Tests Affected by Trace Contamination
D4308 Test Method for Electrical Conductivity of Liquid
Hydrocarbons by Precision Meter
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
ProductsandLubricantsandisthedirectresponsibilityofSubcommitteeD02.J0on
Aviation Fuels.
Current edition approved June 10, 2003. Published August 2003. Originally
approved in 1988. Last previous edition approved in 1998 as D4865–98. DOI: Annual Book of ASTM Standards, Vol 05.01.
10.1520/D4865-98R03E01. Annual Book of ASTM Standards, Vol 05.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D4865–98 (2003)
D5191 Test Method for Vapor Pressure of Petroleum Prod- 3.1.9 flammable liquid, n—a liquid having a flash point
ucts (Mini Method) below 38°C (100°F) (seeTest Methods D56 and D93D56D93)
D5452 Test Method for Particulate Contamination in Avia- and having vapor pressure (Test Method D323 or
tion Fuels by Laboratory Filtration D5191D323D5191) not exceeding 276 kPa (40 psia) (see
2.2 National Fire Protection Association (NFPA) Stan- NFPA Standard No. 30).
dards: 3.1.9.1 Discussion—The definition of flammable is cur-
NFPAStandard No. 30 Flammable and Combustible Liquid rentlyunderdiscussionbytheUNCommitteeofExpertsonthe
Code Transportation of Dangerous Goods.
NFPAStandardNo.407 StandardonAircraftFuelServicing 3.1.10 grounding, v—the practice of providing electrical
2.3 Canadian General Standard Board (CGSB) Specifica- continuitybetweenafuelhandlingsystemandgroundorearth.
tion: 3.1.11 high vapor pressure product, n—a product having a
CAN/CGSB 3.6 Regular Sulphur Diesel Fuel vapor pressure above 31 kPa (4.5 psia) (1).
CAN/CGSB 3.517 Automotive Low Sulphur Diesel Fuel 3.1.12 intermediate vapor pressure product, n—a product
2.4 British Standards Institute (BSI) Standard: withavaporpressurebelow31kPa(4.5psia)andaflashpoint
BS5958 (Part2)RecommendationsforParticularIndustrial below 38°C (100°F) (1).
Situations 3.1.13 low vapor pressure product, n—a product with a
flash point above 38°C (100°F) (1).
3. Terminology
3.1.14 relaxation time, n—the time required for a charge to
dissipate to 36.8% of the original value (2).
3.1 Definitions of Terms Specific to This Standard:
3.1.15 residence time, n—thelengthoftimeafterachargeis
3.1.1 bonding, v—the practice of providing electrical con-
generated that a product remains in piping or a closed vessel.
nections between conductive parts of a fuel system to preclude
3.1.16 splash filling, v—the practice of allowing fuel to
voltage differences between the parts.
free-fall or to impinge at high velocity on a tank wall while
3.1.2 bottom loading, v—the practice of filling transport
loading a compartment.
compartments by pumping fuel through a bottom inlet.
3.1.17 static discharge, v—the release of electrical energy
3.1.3 charge accumulation, n—the increase of electrostatic
intheformofasparkorcoronadischargeacrossagapbetween
charges in a tank, compartment, or liquid resulting from a rate
surfaces of differing voltage.
dissipation slower than the rate of charge delivery by the
3.1.18 switch loading, v—the practice of loading one type
incoming product.
of product into a tank or compartment which previously
3.1.4 charge generation, v—the creation of electrostatic
contained a different type of product.
chargesinaliquidduetotheseparationofionicspeciesduring
3.1.18.1 Discussion—When involving handling safety,
liquid flow.
switch loading often refers to loading a low vapor pressure
3.1.5 charge relaxation, n—the decrease of electrostatic
product into a tank or compartment previously containing a
charges with time.
high vapor pressure product. A flammable vapor in the ullage
3.1.6 combustible liquid, n—a liquid having a flash point at
space is likely to result.
or above 38°C (100°F) (See Test Methods D56 and
3.1.19 top loading, v—the practice of filling transport com-
D93D56D93).
partments through an open dome at the top of the transport.
3.1.6.1 Discussion—Subdivisions of this classification will
3.1.20 ullage (vapor) space, n—the space between the
be found in NFPA Standard No. 30.
liquid surface and the top of the tank or compartment contain-
3.1.7 conductivity, n—thereciprocalofelectricalresistivity,
ing the liquid.
the capability to transmit electrostatic charges normally ex-
3.1.21 unbonded charge collector or accumulator,
pressed in picoSiemens per metre (pS/m) for petroleum prod-
n—unbonded, conductive objects which concentrate electrical
ucts.
charges.
3.1.7.1 Discussion—Conductivity has also been expressed
3.1.21.1 Discussion—These unbonded charge collectors
in conductivity units (C.U.) where I.C.U.=1 pS/m=1 310
−1 −1
may be objects floating on the surface of the charged liquid or
−12 V m .
objects such as gaging tapes lowered toward the charged
3.1.8 conductivity improver additive, n— a material added
surface. The high conductivity of metallic charge collectors
to a fuel in very small amounts to increase its electrical
permits the rapid discharge of accumulated charges.
conductivity and thereby reduce relaxation time.
3.1.8.1 Discussion—Conductivity improver additives are
4. Significance and Use
also known as static dissipator additives (SDAs) or antistatic
additives. 4.1 Pumping, filtering, and tank filling of petroleum prod-
ucts, particularly refined distillates, can cause the generation
and accumulation of electrostatic charges and can result in
Annual Book of ASTM Standards, Vol 05.03. static discharges capable of causing fires and explosions. This
Available from National Fire Protection Association (NFPA), 1 Batterymarch
guide provides an overview of the factors involved in the
Park, Quincy, MA 02269-9101.
Available from Canadian General Standard Board, Ottawa, Canada.
Part 2 of British Standard Code of Practice for Control of Undesirable Static
Electricity, available from British Standards Institute, 2 Park St., London, England The boldface numbers in parentheses refer to the references at the end of this
WIA2B5. standard.
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D4865–98 (2003)
generationofsuchelectrostaticcharges.Methodsaredescribed of charge that reaches the tank while relaxation in the tank
for the alleviation of the problem, and cited authoritative reduces the voltage produced by a given amount of inlet
references contain more details. charge. Under most practical loading conditions, the voltage
4.2 Thisguideisnotintendedtoprovideoperatingorsafety generated by a given inlet charge density is proportional to the
rules for the handling of petroleum products to avoid electro- relaxation time of the fuel. This relaxation time is inversely
static hazards. proportional to the conductivity and is approximately 20 s
when the conductivity is 1 pS/m. The conductivity of hydro-
5. Background
carbon fuels is highly variable as a result of natural product
5.1 Ignition Principles:
differences, commingling, or the use of additives. Products not
5.1.1 Forignitiontooccur,itisnecessarytohaveanignition
containing additives, including diesel fuels, may have conduc-
source of sufficient energy and a mixture of fuel and air in the
tivitiesoflessthan1pS/mbutmanymodernadditivepackages
flammable range. The boundaries of the flammable range are
(not just static dissipator additives) provide considerably in-
defined by the lean and rich limits. Below the lean limit there
creased conductivity, possibly up to several hundred pS/m or
is not enough hydrocarbon vapor to sustain combustion,
more. The relaxation time can therefore be anything form a
whereas above the rich limit there is not enough oxygen. The
fraction of a second to a number of minutes. It has been found
mixture temperature and pressure and the fuel characteristics,
that the reduced relaxation time produced by increasing the
including boiling range and vapor pressure, determine the
conductivitymorethancompensatesforanyincreaseincharge
amount of a given fuel which is vaporized and therefore
generation that may occur. The highest voltages and electro-
establishtheflammabilityofthemixture.Normallytheselimits
static ignition risks are therefore associated with low conduc-
are measured under equilibrium conditions with the fuel
tivities. Unless conductivities are controlled, the possibility of
partially or completely vaporized. However, ignitions have
encountering low conductivity product should be allowed for
occurred below the lean ignition limit when the fuel was in the
when defining safe loading procedures (3, 4).
form of a foam or spray. Also, systems are not normally in
6. Practical Problems
equilibrium when there is sufficient fuel flow to generate
electrostaticcharges.Turbulenceinthevaporspacecanleadto 6.1 Certain switch loading operations, such as loading of
unexpected flammable air-vapor mixtures in localized areas. diesel fuel into a truck which previously carried gasoline and
Equilibrium flammability limits can therefore be used only as still contains vapors or liquid gasoline, are especially danger-
rough guidelines of flammability. ous.The combination of a flammable vapor space and charged
5.1.2 The second requirement for ignition is a static dis- diesel fuel presents a potential explosion hazard if an electro-
charge of sufficient energy and duration. Discharges occur static discharge occurs. Analyses (5) of past tank truck acci-
when the voltage across a gap exceeds the breakdown strength dents reveal that switch loading or splash filling, or both,
of the fluid or air in the gap. Minimum energy requirements account for 80% of static-initiated explosions. More informa-
vary widely depending on the nature of the spark, the configu- tion on the hazards of flammable atmospheres formed during
ration of the spark gap and electrodes, nature of materials, and switch loading will be found in 7.6.
other factors. There is no doubt that sparks due to static 6.2 Microfilters and filter-separators are prolific generators
electricity in petroleum systems can have sufficient energy to of electrostatic charges. The type of ionic impurity in the
igniteflammablemixtures when they occur in the vaporspace. product as well as the type of surface determine the magnitude
Discharges from highly charged fluids are known to penetrate and polarity of separated charges that are swept away in the
plastic tubing. flowing stream. Many additives in fuel increase the level of
5.2 Charge Generation—Whenever a hydrocarbon liquid charge generation upon filtration, although in the case of static
flows with respect to another surface, a charge is generated in dissipatoradditivesthisismorethancompensatedbyenhanced
the liquid and an equal but opposite charge is imposed on that charge dissipation. Most common filter media such as fiber-
surface. This charge is attributed to ionic impurities present in glass, paper, and cloth as well as solid adsorbents are potent
parts per million or parts per billion quantities. At rest the chargegenerators.Whencarryingoutoperationssuchasmeter
impurities are adsorbed at the interface between the fuel and provingthatinvolvetheuseoftemporaryormobileequipment,
the container walls, with one part of the ionic material having care should be taken not to introduce filters without adequate
a strong attachment for the fuel or the container. Under these residence time (6).
conditions, there is no net charge on the fuel. However, when 6.3 Flow
...
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