ASTM D4888-06(2011)
(Test Method)Standard Test Method for Water Vapor in Natural Gas Using Length-of-Stain Detector Tubes
Standard Test Method for Water Vapor in Natural Gas Using Length-of-Stain Detector Tubes
SIGNIFICANCE AND USE
The measurement of water vapor in natural gas is important because of the gas quality specifications, the corrosive nature of water vapor on pipeline materials, and the effects of water vapor on utilization equipment.
This test method provides inexpensive field screening of water vapor. The system design is such that it may be used by nontechnical personnel with a minimum of proper training.
SCOPE
1.1 This test method covers a procedure for rapid and simple field determination of water vapor in natural gas pipelines. Availabel detector tubes provide a total measuring range of 0.1 to 40 mg/L, although the majority of applications will be on the lower end of this range (that is, under 0.5 mg/L). At least one manufacturer provides tubes that read directly in pounds of water per million cubic feet of gas. See Note 1.
1.2 Detector tubes are usually subject to interferences from gases and vapors other than the target substance. Such interferences may vary among brands because of the use of different detection methods. Consult manufacturer's instructions for specific interference information. Alcohols and glycols will cause interferences on some water vapor tubes because of the presence of the hydroxyl group on those molecules.
1.3 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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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D4888 − 06(Reapproved 2011)
Standard Test Method for
Water Vapor in Natural Gas Using Length-of-Stain Detector
Tubes
This standard is issued under the fixed designation D4888; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
NOTE 1—Detector tubes are available with calibration scales printed in
1. Scope
pounds of water per million cubic feet of gas (lb/MMCF). The conversion
1.1 This test method covers a procedure for rapid and
factor is 1 mg/L = 62.3 lb/MMCF (7 lb/MMCF = 0.11 mg/L).
simple field determination of water vapor in natural gas
pipelines. Availabel detector tubes provide a total measuring 3. Significance and Use
range of 0.1 to 40 mg/L, although the majority of applications
3.1 The measurement of water vapor in natural gas is
will be on the lower end of this range (that is, under 0.5 mg/L).
important because of the gas quality specifications, the corro-
At least one manufacturer provides tubes that read directly in
sive nature of water vapor on pipeline materials, and the effects
pounds of water per million cubic feet of gas. See Note 1.
of water vapor on utilization equipment.
1.2 Detector tubes are usually subject to interferences from
3.2 This test method provides inexpensive field screening of
gases and vapors other than the target substance. Such inter-
water vapor. The system design is such that it may be used by
ferencesmayvaryamongbrandsbecauseoftheuseofdifferent
nontechnical personnel with a minimum of proper training.
detection methods. Consult manufacturer’s instructions for
specific interference information. Alcohols and glycols will
4. Apparatus
cause interferences on some water vapor tubes because of the
4.1 Length-of-Stain Detector Tubes—A sealed glass tube
presence of the hydroxyl group on those molecules.
with the breakoff tips sized to fit the tube holder of the pump.
1.3 This standard does not purport to address all of the
Thereagentlayerinsidethetube,typicallyasilicagelsubstrate
safety concerns, if any, associated with its use. It is the
coated with the active chemical, must be specific for water
responsibility of the user of this standard to establish appro-
vapor and produce a distinct color change when exposed to a
priate safety and health practices and determine the applica-
sample of gas containing water vapor. Any substances known
bility of regulatory limitations prior to use.
to interfere must be listed in the instructions accompanying the
tubes. A calibration scale should be marked directly on the
2. Summary of Test Method
tube; however, other markings that provide for ready interpre-
2.1 The sample is passed through a detector tube filled with
tation of water vapor content from a separate calibration scale
a specially prepared chemical. Any water vapor present in the
supplied with the tubes shall be acceptable. The calibration
sample reacts with the chemical to produce a color change or
scale shall correlate water vapor concentration to the length of
stain. The length of the stain produced in the detector tube,
the color stain. Shelf life of the detector tubes must be a
when exposed to a measured volume of sample, is directly
minimum of two years from date of manufacture when stored
proportional to the amount of water vapor present in the
according to manufacturers’ recommendations.
sample. A hand-operated piston or bellows-type pump is used
4.2 Detector Tube Pump—A hand-operated pump of a
to draw a measured volume of sample through the tube at a
piston or bellows type. It must be capable of drawing 100 mL
controlled rate of flow. The length of stain produced is
per stroke of sample through the detector tube with a volume
converted to milligrams per litre of H O by comparison to a
tolerance of 65 mL. It must be specifically designed for use
calibration scale supplied by the manufacturer for each box of
with detector tubes.
detection tubes. The system is direct reading, easily portable,
and completely suited to making rapid spot checks for water
NOTE 2—A detector tube and pump together form a unit and must be
used as such. Each manufacturer calibrates detector tubes to match the
vapor under field conditions.
flow characteristics of its specific pump. Crossing brands of pumps and
tubes is not permitted, as considerable loss of system accuracy is likely to
This test method is under the jurisdiction of CommitteeD03 on Gaseous Fuels 2
occur.
and is the direct responsibility of Subcommittee D03.07Analysis of Chemical
Composition of Gaseous Fuels.
CurrenteditionapprovedNov.1,2011.PublishedJuly2012.Originallyapproved
in 1988. Last previous edition approved in 2006 as D4888 – 06. DOI: 10.1520/ Direct Reading Colorimetric Indicator Tubes Manual , First ed., American
D4888-06R11. Industrial Hygiene Association, Akron, OH 44311, 1976.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4888 − 06 (2011)
4.3 Gas Sampling Chamber—Any container that provides tubing is preferred. (Warning— Exiting gases are highly
for access of the detector tube into a uniform flow of sample flammable and may contain toxic levels of hydrogen sulfide.
gas at atmospheric pressure and isolates the sample from the Consider venting the exit gases away from the user when
surrounding atmosphere. A stainless steel needle valve (or possible.)
pressure regulator) is placed between the source valve and the
5.3 Open source valve. Open needle valve enough to obtain
sampling chamber for the purpose of throttling the sample
positive flow of gas chamber, in accordance with 4.3. Purge the
flow.Flowrateshouldapproximateonetotwovolumechanges
container for at least 3 min (Fig. 1). Purge for at least 10 min
per minute or, at minimum, provide exit gas flow throughout
if a polyethylene bottle is used.
the detector tube sampling period.
5.4 Before each series of measurements, test the pump for
NOTE 3—Asuitable chamber may be devised from a polyethylene wash
leaks by operating it with an unbroken tube in place. Consult
bottle of nominal 500-mL (16-oz) or 1-L (32-oz) size. The wash bottle’s
manufacturers’ instructions for leak check procedure details
internal delivery tube provides for delivery of sample gas to the bottom of
1 and for maintenance instruction if leaks are detected. The leak
the bottle. A ⁄2-in. hole cut in the bottle’s cap provides access for the
detector tube and vent for the purge gas (Fig. 1). check typically takes 1 m
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