1、Designation: D 6273 08Standard 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 number in parenthese
2、s 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 mix the sampled n
3、atural 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, if any, associate
4、d 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:2D 4150 Terminology Relating to Gaseous FuelsD 5287 Practice fo
5、r Automatic Sampling of Gaseous FuelsE 253 Terminology Relating to Sensory Evaluation of Ma-terials and Products2.2 Other Standards49 CFR Part 192.625 Odorization of gas33. Terminology3.1 Definitions:3.1.1 odorant, nsulfur-bearing compound that gives natu-ral gas a distinctive odor. For the purpose
6、of these test methods,natural gas odorants 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
7、 to an odor, a mixture of odors, orseries 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 inle
8、t pressure specified by the manufacturer 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
9、 the manu-facturer of the gas dilution 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 concentra
10、tion of natu-ral gas and odorant mixture 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 na
11、tural gas that areused in these test methods, 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 regulations (49 CFR Part 192.625) state: “Acombustible gas in a distribut
12、ion line must contain a naturalodorant or be odorized so that at a concentration in air ofone-fifth of the lower explosive limit, the gas is readilydetectable by a person with a normal sense of smell.” Theseregulations state further that “each operator shall conductperiodic sampling of combustible g
13、ases to assure the properconcentration of odorant in accordance with this section.”Additionally, a number of states have enacted legislation that1These test methods are under the jurisdiction of Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.05 on Determination of
14、Special Constituents of Gaseous Fuels.Current edition approved May 1, 2008. Published May 2008. Originallyapproved in 1998. Last previous edition approved in 2003 as D 6273 98(2003).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.o
15、rg. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http:/www.dodssp.daps.mil.1Copyright ASTM Internati
16、onal, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.requires natural gas to be odorized so that it is detectable atconcentrations less than one fifth of the lower explosive limit.See note Note 1. While regulations do not specify the exactmethod for determining c
17、ompliance, it has been documentedthat compliance testing must be olfactory in nature.4NOTE 1For example, Massachusetts Section 192.625 MFS Standardsrequires that “. a concentration of fifteen hundredths of one percent gasin the air is readily perceptible to the normal or average olfactory sensesof a
18、 person . .”4.2 These test methods cover procedures to measure 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
19、-pounds in natural gas.4.3 These test methods outline general procedures 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
20、 all appropriate regula-tions.5. Interferences and Precautions5.1 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 o
21、f odor.5.2 Operators shall be trained to perform odor testing ofnatural 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 n
22、ot chewtobacco or gum or eat food of pungent taste or odor for 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 tim
23、e shall be allotted between teststo ensure that the testers sense 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 meth
24、od to determinethe relative concentration of the gas/air mixture. 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 g
25、as dilution apparatus as specified bythe manufacturer. This regulator 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
26、function satisfactorily.6.2.1 The gas dilution apparatus shall 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 reg
27、ulator shall be a heated regulator when com-pressed natural gas (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 s
28、ample line shall be clean andconsist of material that is inert 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 li
29、nes include stainless steel, alumi-num, urethane, PTFE, PVC, and 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 constr
30、uctionand installation.)7. Hazards7.1 Because these test methods 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
31、for the instrumentation used inthese test methods may result in 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.7.3 Cautio
32、n must be exercised in selecting appropriateinstrumentation used in application of this test method. Odorintensity instrumentation should be operated and suited for theintended use including suitability to area classification andmeasurement environment.8. Sampling8.1 Location:8.1.1 The location shal
33、l be far enough from an odorizingstation 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 po
34、ints also shall be selected 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:4American Gas Association Operating Section Technical
35、Note CAS-2-1-95, “Natural Gas Odorization: Compliance with Federal Regulations.”D62730828.3.1 In low-pressure sampling, the gas dilution apparatus isconnected directly to the gas source with the appropriate tubingas specified in 6.3. Connections shall be made to the appropri-ate gas dilution apparat
36、us 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 source with the appropriate tubing asspecified in 6.3.8.4.1.1 In addition to other precautions, the gas pressureshould be taken into cons
37、ideration when selecting the tubingthat connects the gas source with the inlet of the regulator.Stainless 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 con
38、densation.NOTE 2A 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
39、performedevery 30 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
40、.4 If an odor is 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 ma
41、nufac-turers instructions.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 dilut
42、ionapparatus is in 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 swi
43、tch to the“ON” position.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 determi
44、nation as specified 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 wi
45、th manufacturers 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 manufa
46、cturersinstructions. 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
47、 gas inletvalve to 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 det
48、ected, allow the 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 i
49、s achieved.10.3.7 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 3Other odor intensity rating terms may be used as appropriate.NOTE 4If this test is performed independently of the odor 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 B
