1、Designation: D 4810 06Standard Test Method forHydrogen Sulfide in Natural Gas Using Length-of-StainDetector Tubes1This standard is issued under the fixed designation D 4810; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for a rapid andsimple field determination of hydrogen sulfide in natural gaspi
3、pelines. Available detector tubes provide a total measuringrange of 0.5 ppm by volume up to 40 % by volume, althoughthe majority of applications will be on the lower end of thisrange (that is, under 120 ppm).1.2 Typically, sulfur dioxide and mercaptans may causepositive interferences. In some cases,
4、 nitrogen dioxide cancause a negative interference. Most detector tubes will have a“precleanse” layer designed to remove certain interferences upto some maximum interferent level. Consult manufacturersinstructions for specific interference information.1.3 The values stated in SI units are to be rega
5、rded as thestandard.1.4 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 of regulatory limitations prior to
6、 use.2. Referenced Documents2.1 Gas Processors Association Standard:No. 2377-86 Test for Hydrogen Sulfide in Natural GasUsing Length of Stain Tubes23. Summary of Test Method3.1 The sample is drawn through a detector tube filled witha specially prepared chemical. Any hydrogen sulfide present inthe sa
7、mpling reacts with the chemical to produce a colorchange or stain. The length of the stain produced in the detectortube, when exposed to a measured volume of sample, isdirectly proportional to the amount of hydrogen sulfide presentin the sample. A hand-operated piston or bellows-type pump isused to
8、draw a measured volume of sample through the tube ata controlled rate of flow. The length of stain produced isconverted to ppm (by volume) hydrogen sulfide (H2S), bycomparison to a calibration scale supplied by the manufacturerfor each box of detection tubes (higher range tubes have unitsof percent
9、by volume). The system is direct reading, easilyportable, and completely suited to making rapid spot checks forhydrogen sulfide under field conditions.4. Significance and Use4.1 The measurement of hydrogen sulfide in natural gas isimportant because of the gas quality specifications, the corro-sive n
10、ature of H2S on pipeline materials, and the effects of H2Son utilization equipment.4.2 This test method provides inexpensive field screening ofhydrogen sulfide. The system design is such that it may be usedby nontechnical personnel with a minimum of proper training.5. Apparatus5.1 Length-of-Stain De
11、tector Tube and CalibrationScaleA sealed glass tube with breakoff tips sized to fit thetube holder of the pump. The reagent layer inside the tube,typically a silica gel substrate coated with the active chemicals,must be specific for hydrogen sulfide and must produce adistinct color change when expos
12、ed to a sample of gascontaining hydrogen sulfide. Any substances known to inter-fere must be listed in the instructions accompanying the tubes.A calibration scale should be marked directly on the tube orother markings which provide for easy interpretation of hydro-gen sulfide content from a separate
13、 calibration scale suppliedwith the tubes. The calibration scale shall correlate hydrogensulfide concentration to the length of the color stain. Shelf lifeof the detector tubes must be a minimum of two years fromdate of manufacture when stored according to manufacturersrecommendations.5.2 Detector T
14、ube PumpA hand-operated pump of apiston or bellows type. It must be capable of drawing 100 cm3per stroke of sample through the detector tube with a volumetolerance of 65cm3.3It must be specifically designed for usewith detector tubes.NOTE 1A detector tube and pump together form a unit and must be1Th
15、is test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.07 on Analysis ofChemical Composition of Gaseous Fuels.Current edition approved June 1, 2006. Published June 2006. Originallyapproved in 1988. Last previous edition appr
16、oved in 1999 as D 4810 - 98 (1999).2Available from Gas Processors Association, 1812 First National Bank Bldg.,Tulsa, OK 74103.3Direct Reading Colorimetric Indicator Tubes Manual , 1st ed., AmericanIndustrial Hygiene Association, Akron, OH 44311, 1976.1Copyright ASTM International, 100 Barr Harbor Dr
17、ive, PO Box C700, West Conshohocken, PA 19428-2959, United States.used as such. Each manufacturer calibrates detector tubes to match theflow characteristics of their specific pump. Crossing brands of pumps andtubes is not permitted, as considerable loss of system accuracy is likely tooccur.3(Note th
18、at at least one manufacturer allows extended samples upto 100 pumpstrokes to obtain lower detection levels. This may beautomated for screening purposes by drawing the sample from an inertcollapsable container by vacuum displacement. The sample flow rateshould be maintained within 65 % of the manufac
19、turers specified flowrate. Accuracy losses are apt to occur in such special applications, andsuch a system is recommended only for screening purposes. Consultmanufacturers regarding limitations.)5.3 Gas Sampling ChamberAny container that providesfor access of the detector tube into a uniform flow of
20、 samplegas at atmospheric pressure and isolates the sample from thesurrounding atmosphere. A stainless steel needle valve (orpressure regulator) is placed between the source valve and thesampling chamber for the purpose of throttling the sampleflow. Flow rate should approximate one to two volume cha
21、ngesper minute or, at minimum, provide positive exit gas flowthroughout the detector tube sampling period.NOTE 2A suitable sampling chamber may be devised from a poly-ethylene wash bottle of nominal 500-mL (16-oz) or 1-L (32-oz) size. Thewash bottles internal delivery tube provides for delivery of t
22、he sample gasto the bottom of the bottle. A 12.5-mm (12-in.) hole cut in the bottles capprovides access for the detector tube and vent for the purge gas (Fig. 1).(An alternate flow-through sampler may be fashioned using a 1-galZiploc-type food storage bag. The flexible line enters one corner of theb
23、ags open end and extends to the bottom of the bag. The opposite cornerof the open end is used for tube access and sample vent. The remainder ofthe bags top is sealed shut. The basic procedure for the sampler in Fig. 1applies.)NOTE 3An alternate sampling container is a collection bag made of amateria
24、l suitable for the collection of natural gas (for example, Mylar).The sampling bag should have a minimum capacity of 2 L.6. Procedure6.1 Select a sampling point that will provide access to arepresentative sample of the gas to be tested (for example,source valve on the main line). The sample point sh
25、ould be ontop of the pipeline and equipped with a stainless steel sampleprobe extending into the middle third of the pipeline. Open thesource valve momentarily to clear the valve and connectingnipple of foreign materials.6.2 Install needle valve (or pressure regulator) at the sourcevalve outlet. Con
26、nect sampling chamber using the shortestlength of flexible tubing possible (Fig. 1). Avoid using tubingthat reacts with or absorbs H2S, such as copper or naturalrubber. Use materials such as TFE-fluorocarbon, vinyl, poly-ethylene, or stainless steel.6.3 Open source valve. Open needle valve enough to
27、 obtainpositive flow of gas through chamber, in accordance with 5.3.Purge the container for at least 3 min (Fig. 1).NOTE 4If a collection bag is used instead of a sampling chamber,follow 6.1 and 6.2, substituting the bag for the chamber. Follow 6.3,disconnecting the bag when filled. Deflate the bag
28、to provide a purge, andfill a second time to provide a sample. The bag must be flattenedcompletely before each filling (Note 3).6.4 Before each series of measurements, test the pump forleaks by operating it with an unbroken tube in place. Consultthe manufacturers instructions for leak check procedur
29、e de-tails and for maintenance instruction, if leaks are detected. Theleak check typically takes 1 min.6.5 Select a detector tube with the range that best encom-passes the expected H2S concentration. Reading accuracy isimproved when the stain length extends into the upper half ofthe calibration scal
30、e. Consult manufacturers guidelines forusing multiple strokes to achieve a lower range on a given tube.6.6 Break off the tube tips and insert the tube into the pump,observing the flow direction indication on the tube. Place thedetector tube into the sampling chamber through the accesshole, so that t
31、he tube inlet is near the chamber center (Fig. 1).NOTE 5Detector tubes have temperature limits of 0 to 40C (32 to104F), and sample gases must remain in that range throughout the test.Cooling probes are available for sample temperatures exceeding 40C.6.7 Operate the pump to draw the measured sample v
32、olumethrough the detector tube. Observe tube instructions whenapplying multiple strokes. Assure that a positive flow ismaintained throughout the sample duration at the samplingchamber gas exit vent. Observe tube instructions for propersampling time per pump stroke. The tube inlet must remain inposit
33、ion inside the sampling chamber until the sample iscompleted. Many detector tube pumps will have stroke finishindicators that eliminate the need to time the sample.NOTE 6If a collection bag is used, the sample is drawn from the bagvia a flexible tubing connection. Do not squeeze the bag during sampl
34、ing.Allow the bag to collapse under pump vacuum, so that the pumps flowcharacteristics are not altered.6.8 Remove the tube from the pump and immediately readthe H2S concentration from the tubes calibration scale or fromthe charts provided in the box of tubes. Read the tube at themaximum point of the
35、 stain. If “channeling” has occurredFIG. 1 Apparatus SchematicD4810062(nonuniform stain length), read the maximum and minimumstain lengths and average the two readings.NOTE 7If the calibration scale is not printed directly on the detectortube, be sure that any separate calibration chart is the prope
36、r match for thetube in use.6.9 If the number of strokes used differs from the number ofstrokes specified for the calibration scale, correct the reading,as below:ppm corrected!5ppm reading!3specified strokesactual strokes(1)6.10 Record the reading immediately, along with the gastemperature and the ba
37、rometric pressure. Observe any tem-perature corrections supplied in the tube instructions. Altitudecorrections become significant at elevations above 2000 ft.Correct for barometric pressure, as below:ppm corrected!5ppm reading!3760 mm Hgbarometric pressure in mm Hg(2)NOTE 8Although the amount of che
38、micals contained in detector tubesis very small, the tubes should not be disposed of carelessly. A generaldisposal method includes soaking the opened tubes in water before tubedisposal. The water should be pH neutralized before its disposal.7. Quality Assurance7.1 Detector tubes from each batch or l
39、ot of tubes should betested to conform the published accuracy, (generally 6 25 %).7.2 The tubes should continue to meet the published accu-racy until the expiration date, if the tubes are shipped andstored per manufacturer instructions.8. Precision and Bias8.1 The accuracy of detector tube systems i
40、s generallyconsidered to be 625 %. This value is based on programsconducted by the National Institute of Occupational Safety andHealth (NIOSH) in certifying detector tubes for low-levelcontaminants in air, adapted to worker exposure monitoring.4NIOSH tested tubes at12 , 1, 2, and 5 times the thresho
41、ld limitvalue (TLV) requiring 625 % accuracy at the three higherlevels and 635 % at the12 TLV level.5(For example, H2S witha TLV of 10 ppm was tested at levels of 5, 10, 20, and 50 ppm.)The higher tolerance allowed at the low level was due to theloss of accuracy for shorter stain lengths.3NIOSH disc
42、ontin-ued this program in 1983, and it was picked up by the SafetyEquipment Institute (SEI) in 1986.8.1.1 The Gas Processors Association Standard No. 2377for natural gas testing via H2S detector tubes summarizesdetector tube accuracy testing in natural gas in which allreported results are within 623
43、 %.8.2 RepeatabilityDuplicate results by the same operator,under the same test conditions, should produce results within610 % between 3- and 120-ppm H2S and 65 % between 0.05and 5 % H2S (see GPA No. 2377). Repeatability is optimizedwhen all tests using a single brand are conducted with detectortubes
44、 of the same lot number.9. Keywords9.1 gaseous fuels; natural gasASTM 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 su
45、ch patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invit
46、ed either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a
47、 fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this
48、 standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).4Septon, J. C. and Wilczek, T., “Evaluation of Hydrogen Sulfide DetectorTubes,” App. Ind. Hyg., Vol. 1, No. 4, 11/86.5“NIOSH Certification Requirements for Gas Detector Tube Units,” NIOSH/TC/A-012, 7/78.D4810063
