1、Designation: D 6273 98 (Reapproved 2003)Standard Test Methods forNatural Gas Odor Intensity1This standard is issued under the fixed designation D 6273; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the procedures for determin-ing the odor intensity of natural gas through the use ofinstruments that dilute and
3、 mix the sampled natural gas withair. The mixed gas stream is then sniffed by the operator for thepurpose of determining the threshold detection level or thereadily detection level, or both, for odorant in the natural gasstream.1.2 This standard does not purport to address all of thesafety concerns,
4、 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 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 4150 Terminology Relating to Gaseous Fuels2
5、D 5287 Practice for Automatic Sampling of Gaseous Fuels2E 253 Terminology Relating to Sensory Evaluation of Ma-terials and Products33. Terminology3.1 Definitions:3.1.1 odorant, nsulfur-bearing compound that gives natu-ral gas a distinctive odor. For the purpose of these test methods,natural gas odor
6、ants may be compounds that are present at thewellhead or commercial mixtures that are added to the gasstream, or both.3.1.2 olfactory fatigue, ndesensitization of the sense ofsmell through either prolonged exposure or repeated exposureover a short period of time to an odor, a mixture of odors, orser
7、ies of odors.3.1.3 sniff, vismell or snuff with short, audible inhala-tions.3.2 Definitions of Terms Specific to This Standard:3.2.1 high pressure, nfor the purpose of these test meth-ods, high pressure refers to natural gas pressure greater than themaximum inlet pressure specified by the manufactur
8、er of thegas dilution apparatus.3.2.2 intensity, nthe magnitude of odor perceived by theoperator.3.2.3 low pressure, nfor the purpose of these test meth-ods, low pressure refers to natural gas pressure less than orequal to the maximum inlet pressure specified by the manu-facturer of the gas dilution
9、 apparatus.3.2.4 operator(s), nthe person(s) performing the testingdescribed in these test methods. Because of the nature of thetesting described herein, the operator shall be qualified toperform this work (see 5.2).3.2.5 readily detectable level, nthe concentration of natu-ral gas and odorant mixtu
10、re in air which the operator is able todetect and identify natural gas odor.3.2.6 threshold detection level, nthe concentration ofnatural gas and odorant mixture in air which the operator isbarely able to detect an odor.3.3 For definitions of terms related to natural gas that areused in these test m
11、ethods, refer to Practice D 5287.3.4 For definitions of terms related to olfactory testing thatare used in these test methods, refer to Terminology E 253.4. Significance and Use4.1 Federal regulations4state: “A combustible gas in adistribution line must contain a natural odorant or be odorizedso tha
12、t at a concentration in air of one-fifth of the lowerexplosive limit, the gas is readily detectable by a person witha normal sense of smell.” These regulations state further that“each operator shall conduct periodic sampling of combustiblegases to assure the proper concentration of odorant in accor-
13、dance with this section.” Additionally, a number of states haveenacted legislation that requires natural gas to be odorized sothat it is detectable at concentrations less than one fifth of thelower explosive limit.5While regulations do not specify the1These test methods are under the jurisdiction of
14、 Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.05 on Determination ofSpecial Constituents of Gaseous Fuels.Current edition approved Sept. 10, 2003. Published October 2003. Originallyapproved in 1998. Last previous edition approved in 1998 as D 6273 98.2Annual Boo
15、k of ASTM Standards, Vol 05.06.3Annual Book of ASTM Standards, Vol 15.08.449 CFR Part 192.625.5For example, Massachusetts Section 192.625 MFS Standards requires that “.a concentration of fifteen hundredths of one percent gas in the air is readilyperceptible to the normal or average olfactory senses
16、of a person . .”1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.exact method for determining compliance, it has been docu-mented that compliance testing must be olfactory in nature.64.2 These test methods cover procedures to measure
17、theodor level of natural gas by way of olfactory determination. Nodirect correlation may be ascertained between these testmethods and those methods available or under developmentthat quantitatively measure the concentration of sulfur com-pounds in natural gas.4.3 These test methods outline general p
18、rocedures to mea-sure the odor detection levels of natural gas. It is the respon-sibility of persons using these test methods to develop andmaintain equipment and specific operating procedures to en-sure public safety and compliance with all appropriate regula-tions.5. Interferences and Precautions5
19、.1 The location to be tested should be sheltered from windand isolated from sources of interfering odors such as thosefrom certain industrial plants and landfills. The equipment andsampling lines used in testing shall be clean and free of odor.5.2 Operators shall be trained to perform odor testing o
20、fnatural gas and in the proper use and care of test instrumenta-tion. It is preferred that operators should be nonsmokers, or, ifsmokers, they shall not smoke for at least 30 min beforeperforming the test. Additionally, operators shall not chewtobacco or gum or eat food of pungent taste or odor for
21、at least30 min before performing the test. Operators should have nocold, allergies, or other physical conditions that would affecttheir sense of smell.5.3 Prolonged use of the sense of smell may result inolfactory fatigue. Sufficient time shall be allotted between teststo ensure that the testers sen
22、se of smell is not adverselyaffected by the previous test.6. Apparatus6.1 Gas Dilution ApparatusThis apparatus shall consistof a gas inlet control valve, a gas/air mixing chamber, a sampleport for sniffing the gas/air mixture, and a method to determinethe relative concentration of the gas/air mixtur
23、e. All compo-nents that come in contact with natural gas shall be inert toodorant compounds.6.2 Natural Gas Pressure Regulator(s)This item may berequired to lower the gas pressure at the sampling location toa level that is safe for the gas dilution apparatus as specified bythe manufacturer. This reg
24、ulator may need to be a heatedregulator if an extremely large pressure drop is required, forexample, when compressed natural gas or gas at transmissionline pressure is to be tested. More than one regulator may berequired to perform this function satisfactorily.6.2.1 The gas dilution apparatus shall
25、never be subjected tonatural gas pressures greater than that specified by the manu-facturer. Excessive natural gas pressure may result in instru-ment failure and cause an excessive amount of gas to vent outof the instrument.6.2.2 The regulator shall be a heated regulator when com-pressed natural gas
26、 (CNG) is to be tested or when it isanticipated that liquid hydrocarbons may condense from thegas stream as a result of Joule-Thompson Expansion. Odorantcompounds have a preference for liquid hydrocarbons whenpresent.6.3 Sample LineThe sample line shall be clean andconsist of material that is inert
27、to natural gas odorant com-pounds. Sample lines shall be tested periodically by perform-ing a blank determination as specified in 9.1 and replaced asrequired. Rubber or copper tubing shall not be used. Appro-priate material for sample lines include stainless steel, alumi-num, urethane, PTFE, PVC, an
28、d PEK.6.4 Sample ProbeA stainless steel sample probe shall beused where appropriate to prevent the possibility of pipelinecontaminants from entering the sample stream. (See Section 6of Practice D 5287 for specifics on sample probe constructionand installation.)7. Hazards7.1 Because these test method
29、s involve the sampling ofnatural gas and the venting of a gas/air mixture, only qualifiedpersons shall perform the testing described. These test methodsshall not be performed near open flames. Failure to followmanufacturers instructions for the instrumentation used inthese test methods may result in
30、 a hazardous condition.7.2 These test methods shall never be performed at locationsthat potentially contain sour gas. High concentrations ofhydrogen sulfide can quickly poison the operator resulting indeath or permanent injury.8. Sampling8.1 Location:8.1.1 The location shall be far enough from an od
31、orizingstation to ensure that the odorant is well mixed within the gasstream.8.1.2 In systems fed by more than one odorizer, test pointsshall be located to ensure that the odorant concentrationsupplied by each individual odorizer is evaluated.8.1.3 In large systems, test points also shall be selecte
32、d at ornear the end of the system to ensure adequate odorantconcentration.8.2 Frequency:8.2.1 Sampling frequency shall be established in accordancewith applicable regulations and company policy.8.3 Low-Pressure Sampling:8.3.1 In low-pressure sampling, the gas dilution apparatus isconnected directly
33、to the gas source with the appropriate tubingas specified in 6.3. Connections shall be made to the appropri-ate gas dilution apparatus port in accordance with the manu-facturers instructions.8.4 High-Pressure Sampling:8.4.1 In high-pressure sampling, a regulator is connecteddirectly to the gas sourc
34、e with the appropriate tubing asspecified in 6.3.8.4.1.1 In addition to other precautions, the gas pressureshould be taken into consideration when selecting the tubingthat connects the gas source with the inlet of the regulator.6American Gas Association Operating Section Technical Note CAS-2-1-95, “
35、Natural Gas Odorization: Compliance with Federal Regulations.”D 6273 98 (2003)2Stainless steel shall be the only material used for this purposewhen the sampling source is CNG.8.4.2 If a heated regulator is used, then the temperature shallbe set high enough to prevent hydrocarbon condensation.NOTE 1A
36、 regulator set temperature of 140F (60C) has been foundto be adequate in most circumstances.8.4.3 The tubing connection between the regulator outletand the gas dilution apparatus shall be as specified in 8.3.1.9. Calibration and Maintenance9.1 Blank DeterminationThis test should be performedevery 30
37、 days with each gas dilution apparatus.9.1.1 The gas dilution apparatus shall not be connected to anatural gas source.9.1.2 Power on the apparatus and allow air to flow.9.1.3 Sniff at the apparatus exhaust. The nose shall beapproximately three fourths of an inch from the exhaust.9.1.4 If an odor is
38、detected, allow the instrument to operatefor an additional 2 to 3 min, then repeat 9.1.3. If an odor is stilldetected, return the instrument to the manufacturer for repair.9.2 Other calibration and maintenance of the gas dilutionapparatus shall be performed in accordance with the manufac-turers inst
39、ructions.10. Procedure10.1 These procedures may be performed by two persons.When this occurs, one person should operate the gas dilutionapparatus operating valves and the other act as the observer.10.2 Odor Concentration Method:10.2.1 Ensure that the gas inlet valve on the gas dilutionapparatus is i
40、n the closed or “OFF” position.10.2.2 Connect the gas dilution apparatus to the natural gassupply source in accordance with Section 8. Open the gas inletvalve to ensure that air is purged from the sample line. Closethe gas inlet valve.10.2.3 Turn the gas dilution apparatus power switch to the“ON” po
41、sition.10.2.4 Sniff at the apparatus exhaust. The nose shall beapproximately three fourths of an inch from the exhaust.10.2.5 If an odor is detected, allow the instrument to operatefor an additional 2 to 3 min, then repeat 10.2.4. If an odor isstill detected, perform a blank determination as specifi
42、ed in 9.1.10.2.6 Slowly open the gas inlet valve. Periodically sniff thegas/air mixture at the apparatus exhaust. Breathe fresh airthrough the nose between sniffs of the gas-air mixture. Con-tinue until a faint odor is observed. Determine the gas in airconcentration in accordance with manufacturers
43、instructions.This is the threshold detection level.10.2.7 Continue to open the gas inlet valve. Periodicallysniff the gas/air mixture at the apparatus exhaust. Continueuntil a readily detectable odor of gas is observed. Determinethe gas in air concentration in accordance with manufacturersinstructio
44、ns. This is the readily detectable level.10.3 Odor Intensity Method:10.3.1 Ensure that the gas inlet valve on the gas dilutionapparatus is in the closed or “OFF” position.10.3.2 Connect the gas dilution apparatus to the natural gassupply source in accordance with Section 8. Open the gas inletvalve t
45、o ensure that air is purged from the sample line. Closethe gas inlet valve.10.3.3 Turn the gas dilution apparatus power switch to the“ON” position.10.3.4 Sniff at the apparatus exhaust. The nose shall beapproximately three fourths of an inch from the exhaust.10.3.5 If an odor is detected, allow the
46、instrument to operatefor an additional 2 to 3 min, then repeat 10.3.4. If an odor isstill detected, perform a blank determination as specified in 9.1.10.3.6 Slowly open the gas valve. Increase the gas flowthrough the gas dilution apparatus until the desired gasconcentration in air is achieved.10.3.7
47、 Sniff at the apparatus exhaust.10.3.8 Rate the intensity of the odor as: (1) absent, (2)barely detectable, (3) readily detectable, (4) strong, or (5) verystrong or obnoxious.NOTE 2Other odor intensity rating terms may be used as appropriate.NOTE 3If this test is performed independently of the odor
48、concentra-tion method described in 10.2, then the threshold detection level should bedetermined as outlined in 10.2.6 just before performing this test in orderthat a comparative baseline is established by the operator.11. Precision and Bias11.1 Because the values obtained in these test methods arefu
49、nctions of individual sensitivities, interlaboratory tests can-not be interpreted statistically in the usual way, and a generalstatement regarding precision and bias cannot be made.12. Keywords12.1 compressed natural gas (CNG); natural gas; odor;odorant; sensory evaluationASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such righ
