1.1 本试验方法涵盖使用可调谐二极管激光吸收光谱（TDLAS）分析仪（也称为“TDL分析仪”）在线测定天然气中的气相水分浓度湿度测量的特定波长因制造商而异；通常在1000到10之间 000 单个激光器的可调谐范围小于10 nm 纳米。 1.2 工艺流压力范围为700 mbar至700 bar。TDLAS在接近大气的压力下进行（700-2000毫巴表压）；因此，通常需要减压。TDLAS可以在真空条件下进行，效果良好；然而，由于更高的复杂性和水分进入的趋势，样品调节要求不同，本试验方法未涵盖。一般来说，TDL分析仪的通风管能够承受50到200左右的小压力变化 但重要的是要遵守制造商公布的进口压力和排气压力限制。 背压中的大峰值或阶跃可能会影响分析仪读数。 1.3 典型的样品温度范围为-20至65 °C。虽然本标准不包括样品系统设计，但通常将样品传输线加热至50℃左右 °C，以避免与样品传输线壁沿线的水分吸附和解吸相关的浓度变化。 1.4 水分浓度范围为1到10 百万分之000（ppmv）。不太可能使用一个光谱仪单元来测量整个范围。例如，TDL光谱仪的最大测量值可能为1 ppmv，100 ppmv，1000 ppmv，或10 000 ppmv具有不同的准确度和不同的检测下限。 1.5 TDL吸收光谱测量摩尔比，如ppmv或摩尔百分比。体积比（ppmv和%）与压力无关。 在标准温度和压力（STP）等特定条件下，可以从ppmv中得出每体积单位的重量，例如每标准立方米的水毫克数或每标准立方英尺的水磅数。对于不同的地区和实体，标准条件的定义可能不同。露点可根据ppmv和压力估算。参考测试方法 D1142 和ISO 18453。 1.6 单位- 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.7 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 第节给出了一些具体的危害说明 8. 关于危险。 1.8 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 对天然气中的水分进行测量，以确保天然气采购合同中的水分水平足够低，并防止腐蚀。水分也可能有助于水合物的形成。 5.2 应用TDLAS测量天然气中水分的意义在于，TDLAS分析仪在许多天然气流中可能具有非常高的选择性和最小的干扰。此外，分析仪的传感部件不会被天然气弄湿，从而限制了硫化氢（H 2. S） 以及乙二醇或压缩机油等液体污染物。因此，TDLAS分析仪能够以相对快速的响应检测浓度变化。应注意，如果大量冷凝液进入样品池，TDLAS分析仪的反射镜可能会受到污染。在大多数情况下，无需重新校准或重新校准即可清洁后视镜。 5.3 本方法涵盖的主要应用程序列于 5.3.1 – 5.3.3 . 每种应用可能对气体取样有不同的要求和方法。此外，不同的天然气应用可能具有独特的光谱考虑。 5.3.1 未净化天然气存在于生产、收集场所和天然气处理厂的入口，其特点是潜在的高水位（H 2. O） ，二氧化碳（CO 2. )，硫化氢（H 2. S） 和重烃。 气体调节装置和垫木通常用于移除H 2. O、 CO公司 2. H 2. S、 和其他污染物。脱水后的典型水分浓度约为20至200 ppmv。有必要防止样品管线中的重烃和二醇等液体携带物，以防止细胞或样品成分中的液体聚集。 5.3.2 地下储气设施是用于储存大量天然气以供高峰需求期间使用的高压洞穴。地下储存洞室的压力可高达275巴。通常需要多级加热调节系统来克服样品中气体膨胀引起的显著温度下降。 5.3.3 在运输管道、天然气配送（公用事业）和天然气发电厂入口中发现了高质量的“销售天然气”。这种气体的特点是甲烷百分比非常高（90%-100%），含有少量其他碳氢化合物和微量污染物。

1.1 This test method covers online determination of vapor phase moisture concentration in natural gas using a tunable diode laser absorption spectroscopy (TDLAS) analyzer also known as a “TDL analyzer.” The particular wavelength for moisture measurement varies by manufacturer; typically between 1000 and 10 000 nm with an individual laser having a tunable range of less than 10 nm. 1.2 Process stream pressures can range from 700-mbar to 700-bar gage. TDLAS is performed at pressures near atmospheric (700- to 2000-mbar gage); therefore, pressure reduction is typically required. TDLAS can be performed in vacuum conditions with good results; however, the sample conditioning requirements are different because of higher complexity and a tendency for moisture ingress and are not covered by this test method. Generally speaking, the vent line of a TDL analyzer is tolerant to small pressure changes on the order of 50 to 200 mbar, but it is important to observe the manufacturer’s published inlet pressure and vent pressure constraints. Large spikes or steps in backpressure may affect the analyzer readings. 1.3 The typical sample temperature range is -20 to 65 °C in the analyzer cell. While sample system design is not covered by this standard, it is common practice to heat the sample transport line to around 50 °C to avoid concentration changes associated with adsorption and desorption of moisture along the walls of the sample transport line. 1.4 The moisture concentration range is 1 to 10 000 parts per million by volume (ppmv). It is unlikely that one spectrometer cell will be used to measure this entire range. For example, a TDL spectrometer may have a maximum measurement of 1 ppmv, 100 ppmv, 1000 ppmv, or 10 000 ppmv with varying degrees of accuracy and different lower detection limits. 1.5 TDL absorption spectroscopy measures molar ratios such as ppmv or mole percentage. Volumetric ratios (ppmv and %) are not pressure dependent. Weight-per-volume units such as milligrams of water per standard cubic metre or pounds of water per standard cubic foot can be derived from ppmv at a specific condition such as standard temperature and pressure (STP). Standard conditions may be defined differently for different regions and entities. The dew point can be estimated from ppmv and pressure. Refer to Test Method D1142 and ISO 18453. 1.6 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Some specific hazards statements are given in Section 8 on Hazards. 1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Moisture measurement in natural gas is performed to ensure sufficiently low levels for gas purchase contracts and to prevent corrosion. Moisture may also contribute to the formation of hydrates. 5.2 The significance of applying TDLAS for the measurement of moisture in natural gas is TDLAS analyzers may have a very high degree of selectivity and minimal interference in many natural gas streams. Additionally, the sensing components of the analyzer are not wetted by the natural gas, limiting the potential damage from corrosives such as hydrogen sulfide (H 2 S) and liquid contaminants such as ethylene glycol or compressor oils. As a result, the TDLAS analyzer is able to detect changes in concentration with relatively rapid response. It should be noted that the mirrors of a TDLAS analyzer may be fouled if large quantities of condensed liquids enter the sample cell. In most cases the mirror can be cleaned without the need for recalibration or realignment. 5.3 Primary applications covered in this method are listed in 5.3.1 – 5.3.3 . Each application may have differing requirements and methods for gas sampling. Additionally, different natural gas applications may have unique spectroscopic considerations. 5.3.1 Raw natural gas is found in production, gathering sites, and inlets to gas-processing plants characterized by potentially high levels of water (H 2 O), carbon dioxide (CO 2 ), hydrogen sulfide (H 2 S), and heavy hydrocarbons. Gas-conditioning plants and skids are normally used to remove H 2 O, CO 2 , H 2 S, and other contaminants. Typical moisture concentration after dehydration is roughly 20 to 200 ppmv. Protection from liquid carryover such as heavy hydrocarbons and glycols in the sample lines is necessary to prevent liquid pooling in the cell or the sample components. 5.3.2 Underground gas storage facilities are high-pressure caverns used to store large volumes of gas for use during peak demand. Underground storage caverns can reach pressures as high as 275 bar. Multistage and heated regulator systems are usually required to overcome significant temperature drops resulting from gas expansion in the sample. 5.3.3 High-quality “sales gas” is found in transportation pipelines, natural gas distribution (utilities), and natural gas power plant inlets. The gas is characterized by a very high percentage of methane (90 to 100 %) with small quantities of other hydrocarbons and trace levels of contaminates.