ASTM D5305-2018 Standard Test Method for Determination of Ethyl Mercaptan in LP-Gas Vapor.pdf

1、Designation: D5305 12D5305 18Standard Test Method forDetermination of Ethyl Mercaptan in LP-Gas Vapor1This standard is issued under the fixed designation D5305; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis

2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method coversdescribes a rapid and simple procedure using length of stain length-of-stain tubes for fieldmeasurement

3、of ethyl mercaptan in the vapor phase of LP-gas systems.Although length-of-stain tubes are available to detect ethylmercaptan concentrations in the range of 0.5 to 120 parts per million volume (ppmv),by volume, this test method is specificallyapplicable to systems containing 5 ppmv ppm by volume or

4、more of ethyl mercaptan in LP-gas vapors.NOTE 1A chromatographic technique can be used for more precise, quantitative determination of ethyl mercaptan in LP-gas.1.2 The values stated in SI (metric) units are to be regarded as the standard. The values given in parentheses are for informationonly.afte

5、r SI units are provided for information only and are not considered standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvir

6、onmental practices and determine theapplicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards,

7、Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 NFPA Standard:2NFPA 58 Standard for the Storage and Handling of Liquefied Petroleum Gases3. Terminology3.1 Abbreviations:3.1.1 EMethyl mercaptan3.1.2 LP-Gas, LPGliq

8、uefied petroleum gas3.1.3 PTFEpolytetrafluoroethylene3.1.4 TBMt-butyl mercaptan4. Summary of Test Method4.1 Using a manually-operated vacuum pump, a sample of LP-gas from the vapor space of an LP-gas cylinder, storage tank orother closed containment system is drawn through a detector tube made speci

9、fically for detection of mercaptans.The length of stainethyl mercaptan. The length-of-stain (color change) produced in the detector tube when exposed to a measured volume of sampleis directly proportional to the amount of ethyl mercaptan present in the sample being tested. The length of stain length

10、-of-stainproduced in the detector tube is converted to concentration, in parts per million volume (ppmv),by volume, by comparison witha calibration scale provided by the manufacturer of the stain tube.5. Significance and Use5.1 LP-gas is colorless and odorless, and not detectable by normal human sen

11、ses. To provide an olfactory warning in the eventof a leak, LP-gas intended for domestic or commercial fuel use is intentionally odorized so as to be readily detectable well below1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and

12、 is the direct responsibility of SubcommitteeD02.H0 on Liquefied Petroleum Gas.Current edition approved Nov. 1, 2012April 1, 2018. Published February 2013May 2018. Originally approved in 1992. Last previous edition approved in 20072012 asD530597(2007).D5305 12. DOI: 10.1520/D5305-12.10.1520/D5305-18

13、.2 Available from National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA 02169-7471, http:/www.nfpa.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becau

14、seit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appear

15、s at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1flammable or suffocating concentration levels of LP-gas in air. (See Appendix X1.) for important explanations.) The most commonodorant for LP-gas is ethyl me

16、rcaptan. The field use of this test method will rapidly determine the presence and concentration ofethyl mercaptan in LP-gas vapor without the necessity for complex laboratory equipment.6. Interferences6.1 Detector tubes can be subject to interferences from materials other than the target substance.

17、 Methyl mercaptan will likelyinterfere with tubes designed to measure ethyl mercaptan. Because of different detection chemistry by different manufacturers,interferences can vary. Consult the manufacturers instructions for specific interference information and observe any instructionsgiven.6.2 Propyl

18、ene (propene) will cause an interfering (gray) discoloration with some tubes designed for ethyl mercaptan. LP-gasfrom natural gas sources usually does not contain propylene (propene). However, LP-gas produced in refinery operations oftendoes contain propylene (propene). Detector tubes calibrated for

19、 t-butyl mercaptan eliminate this interference, and should be usedif the presence of propylene (propene) is suspected. Some tubes designed for measurement of t-butyl mercaptan are calibrated inmilligrams per cubic metre (mg/m3) and should be converted to ppmv ppm by volume ethyl mercaptan as shown i

20、n Annex A1.6.3 The validity of this test method depends on the ethyl mercaptan in the LP-gas vapor phase being in equilibrium with ethylmercaptan in the LP-gas liquid phase. If LP-gas vapor has recently been vented, or if a significant volume of vapor relative to thetotal volume of the vapor phase i

21、s vented during this test procedure, the concentration of ethyl mercaptan in the vapor phase samplecan be lower than the equilibrium concentration.7. Apparatus7.1 PumpAmanually-operated vacuum pump, capable of drawing 100 mLper stroke of sample through the detector tube withan accuracy of 62.0 mL.62

22、.0 mL.7.2 Detector TubesSealed tubes, made of glass with break-off tips sized to fit the orifice of the pump used (tubes and pumpsfrom different manufacturers shall not be interchanged). The tube used shall be appropriate for the determination of ethylmercaptan and shall produce a distinct color cha

23、nge when exposed to a sample of LP-gas containing ethyl mercaptan. Anysubstance known to interfere shall be listed in instructions accompanying the tubes (see tubes. 5.2). A calibration scale or othermarkings referenced to a scale shall be etched directly on the tube to allow direct interpretation o

24、f ethyl mercaptan concentration.See Note 2.NOTE 2Detector tubes based on the palladium sulfate detection principle are usually calibrated for ethyl mercaptan; detector tubes using mercuricchloride detection chemistry are usually calibrated for t-butyl mercaptan.7.2.1 Detector tubes should be calibra

25、ted for a tube temperature of approximately 20C20 C and normal atmospheric pressure.Shelf life of the detector tubes shall be a minimum of two years when stored according to the manufacturers recommendations.7.2.2 Detector tubes and pumps form an integrally designed unit, that are to be used as a un

26、it. Each manufacturer calibratesdetector tubes to match the flow characteristics of its pump, and the use of one brand of tube with another brand of pump will giveunreliable results.7.3 Gas Sampling ChamberAny container of a material that is not reactive with mercaptan and that provides for access o

27、f thedetector tube into a uniform flow of sample gas at atmospheric pressure and isolated from the surrounding atmosphere. The sizeof the gas sampling chamber shall be large enough that operation of the pump (6.1) does not draw so much vapor through thedetector tube (6.2) relative to the flow of sam

28、ple vapor that atmospheric air is sucked into the sample chamber, diluting the samplebeing tested (see 8.1.3.2).7.3.1 Asuitable container may be devised from a half-litre0.5 Lpolyethylene bottle (see Fig. 1).A6 mm 6 mm outside diameterpolyethylene tubing sealed into the bottle and discharging near t

29、he bottom of the bottle provides for flow into the samplingcontainer. A 12 mm 12 mm hole cut into the cap of the bottle provides both access for the detector tube and a vent for the excessgas flow.7.3.2 Other possible inert materials for the gas sampling chamber and tubing are nylon, polytetrafluoro

30、ethylene (PTFE),chlorinated or fluorinated polyethylene and chlorosulfonated polyethylene.7.4 Needle Valve and TubingAstainless steel needle valve that can be adjusted to control the flow of gas into the gas samplingchamber. Although a stainless steel needle valve is preferred, a pressure regulator

31、may be used in lieu of a needle valve to controlthe flow of gas into the gas sampling chamber. Polyethylene or PTFE-fluorocarbon tubing may be used to connect the needle valveor pressure regulator to the gas sampling chamber.8. Sampling the LP-Gas Vapor Phase8.1 Select a sampling point that provides

32、 access to a representative sample of LP-gas vapor from the container to be sampled.(WarningWhen selecting a sample point, consider the safety aspects of the release of LPGLP-gas vapor.)8.1.1 Open the source valve (ValveAin Fig. 1) and briefly blow down vigorously to clear foreign material from the

33、source valveand connecting nipple. Close the source valve.D5305 1828.1.1.1 Excess venting can result in a lower concentration of ethyl mercaptan in the vapor phase.8.1.2 Install the control valve (Valve B in Fig. 1) or pressure regulator on the outlet of the source valve. Connect outlet of thecontro

34、l valve to the gas sampling chamber using the shortest length practicable of suitable tubing.8.1.3 Open the source valve and then the control valve to obtain a slight positive flow through the gas sampling chamber,venting to atmosphere through the tube access and vent (Vent C in Fig. 1).8.1.3.1 Purg

35、ed gas shall be vented at a suitable rate so that pressure does not build up in the sampling chamber and increasethe flow rate through the detector tube.8.1.3.2 Conversely, the positive flow of LP gas LP-gas vapor shall be sufficient so that operation of the detector tube pump doesnot pull ambient a

36、ir into the gas sampling chamber which would dilute the LP-gas vapor.8.1.4 Purge the gas sampling chamber for at least 3 min 3 min to displace air.8.1.5 Maintain flow of LP-gas during the test procedure in Section 910.9. Preparation of Apparatus9.1 Before sampling, all sampling equipment should be t

37、horoughly clean and dry.9.2 Immediately before each series of tests, test the pump for leak-free operation in accordance with manufacturers instructions.A loss in vacuum on the pump within 60 s 60 s indicates a leak. If a leak occurs, follow the pump manufacturers instructions forresealing the pump

38、and retest. If the pump vacuum cannot be maintained, do not use the pump for testing.10. Procedure10.1 Select the tube range that includes the expected concentration of ethyl mercaptan present in the sample. Reading accuracyis improved when the stain extends at least one-half of the tube length. Con

39、sider multiple strokes or a lower range tube, or both,to achieve this length of stain.10.2 Break off both tips of the glass stain tube and insert the outlet of the tube (indicated by arrow in direction of flow) snuglyinto the pump head. Temperature of tube shall be maintained in the 00 C to 40C40 C

40、range throughout the test.10.3 Insert the detector tube well into the gas sampling chamber through the tube access and vent (Vent C).10.4 Operate the pump to draw a measured amount of sample through the detector tube. Within any limits set by themanufacturers instructions, use multiple strokes to ac

41、hieve a stain extending to approximately one-half the tube length.10.5 Remove the tube from the pump and follow the manufacturers instructions if further handling of the tube is necessary.10.6 Within 30 seconds, 30 s, read the concentration of ethyl mercaptan from graduations on the tube or from cha

42、rts suppliedwith the tube. The scale reading nearest the end of the stain is taken as the appropriate scale reading.FIG. 1 Half Litre Polyethylene or Other Inert BottleD5305 18311. Interpretation of Results11.1 If the number of pump strokes used is different from the number specified by the manufact

43、urer, apply a correction asfollows:corrected ethyl mercaptan concentration5scale reading (1)3specified strokes/actual strokes!corrected ethyl mercaptan concentration (1)5scale reading3specified strokes/actual strokes!11.2 Some detector tubes that may be used in this test method may be calibrated for

44、 other mercaptans in milligrams per cubicmetre (mg/m3). Perform the conversion from mg/m3 of t-butyl mercaptan to ppmv ppm by volume of ethyl mercaptan asdocumented in Annex A1.11.3 Correct the reading for barometric pressure, especially at high altitudes. For details of this correction, see Annex A

45、1.11.4 Readings of concentrations below 5 ppmv 5 ppm by volume may not be reliable, and may warrant further investigation.(See Appendix X2.)NOTE 3This test method is a direct measure of the concentration of ethyl mercaptan in the vapor phase of LP-gas. If the temperature of the systemis known, resul

46、ts can be used to obtain an approximation of the concentration of ethyl mercaptan in the liquid phase. (See Appendix X1.)12. Report12.1 Report the observed tube reading and corrected concentration of ethyl mercaptan in parts per million by volume (ppmv)to the nearest 0.5 ppmv.ppm by volume, and refe

47、rence this test method.13. Precision and Bias13.1 Precision:13.1.1 The precision of this test method as determined by statistical analysis of interlaboratory test results is as follows:13.1.1.1 RepeatabilityThe difference between successive test results, obtained by the same operator using the same

48、apparatusunder constant operating conditions on identical test material, would, in the long run, in the normal and correct operation of thetest method, exceed the following values only in one case in twenty: from 5 to 20 ppmv, 5 ppm to 20 ppm by volume, the largerof 1 ppm 1 ppm or 615 % of the meana

49、verage of the two results; above 20 ppmv, 20 ppm by volume, 620 % of the meanaverageof the two results.13.1.1.2 ReproducibilityThe difference between two single and independent results, obtained by different operators workingin different laboratories on identical test material, would, in the normal and correct operation of the test method, exceed thefollowing value only in one case in twenty: the larger of 1.5 ppmv 1.5 ppm by volume or 620 % of the meanaverage of the tworesults.NOTE 4The preceding repeatability and reproducibility were obtained from s