ASTM D5454-11(R2020) pdf free download

ASTM D5454-11(R2020) pdf free download.Standard Test Method for Water Vapor Content of Gaseous Fuels Using Electronic Moisture Analyzers
1. Scope
1.1 This test method covers the determination of the water vapor content ofgaseous fuels by the use ofelectronic moisture analyzers. Such analyzers commonly use sensing cells based on phosphorus pentoxide, P 2 O 5 , aluminum oxide, Al 2 O 3 , or silicon sensors piezoelectric-type cells and laser based tech- nologies. 1.2 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.3 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions ofTerms Specific to This Standard: 3.1.1 capacitance-type cell—this cell uses aluminum coated with Al 2 O 3 as part of a capacitor. The dielectric Al 2 O 3 film changes the capacity of the capacitor in relation to the water vapor present. Silicone cells also operate on this principal by reporting a capacitance change when adsorbing or desorbing water vapor. 3.1.2 electrolytic-type cell—this cell is composed of two noble metal electrode wires coated with P 2 O 5 . A bias voltage is applied to the electrodes, and water vapor chemically reacts, generating a current between the electrodes proportional to the water vapor present. 3.1.3 piezoelectric-type cell—sensor consists of a pair of electrodes which support a quartz crystal (QCM) transducer. When voltage is applied to the sensor a very stable oscillation occurs. The faces of the sensor are coated with a hygroscopic polymer. As the amount ofmoisture absorbed onto the polymer varies, a proportional change in the oscillation frequency is produced.3.1.4 laser-type cell—consists of a sample cell with an optical head mounted on one end and a mirror mounted on the other; however, some models will not need a mirror to reflect the light wavelength emitted from the laser. The optical head contains a NIR laser, which emits light at a wavelength known to be absorbed by the water molecule. Mounted, the laser is a detector sensitive to NIR wavelength light. Light from the laser passes through the far end and returns to the detector in the optical head. A portion of the emitted light, proportional to the water molecules present, is absorbed as the light transits the sample cell and returns to the detector. 3.1.5 water content—water content is customarily expressed in terms of dewpoint, °F or °C, at atmospheric pressure, or the nonmetric term of pounds per million standard cubic feet, lb/MMSCF. The latter term will be used in this test method because it is the usual readout unit for electronic analyzers. One lb/MMSCF = 21.1 ppm by volume or 16.1 mgm/m 3 of water vapor. Analyzers must cover the range 0.1 to 50 lb ⁄MMSCF. 3.1.6 water dewpoint—the temperature (at a specified pres- sure) at which liquid water will start to condense from the water vapor present. Charts of dewpoints versus pressure and water content are found in Test Method D1142.
5. Apparatus
5.1 The moisture analyzer and sampling system will have the following general specifications: 5.1.1 Sampling System—Most errors involved with moisture analysis can be eliminated with a proper sampling system. 5.1.1.1 A pipeline sample should be obtained with a probe per Method D1145. The sample temperature must be main- tained 2 °C (3 °F) above the dewpoint of the gas to prevent condensation in the sample line or analyzer. Use of insulation or heat tracing is recommended at cold ambient temperatures. 5.1.1.2 Analyzer sensors are very sensitive to contamina- tion. Any contaminants injurious to the sensor must be re- moved from the sample stream before reaching the sensor. This must be done with minimum impact on accuracy or time of response. If the contaminant is an aerosol of oil, glycol, and so forth, a coalescing filter or semipermeable membrane separator must be used. 5.1.2 Construction—Sampling may be done at high or low pressure. All components subject to high pressure must be rated accordingly. To minimize diffusion and absorption, all materials in contact with the sample before the sensor must be made of stainless steel. Tubing of 1 ⁄ 8 -in. stainless steel is recommended. (Warning—Use appropriate safety precautions when sampling at high pressure.) 5.1.2.1 Pressure gages with bourdon tubes should be avoided as a result of water accumulation in the stagnant volume.