1.1 本规程涵盖反渗透装置浓缩液流的Stiff和Davis稳定性指数（S&DSI）的计算和调整。该指数用于确定在反渗透装置的操作和设计中是否需要控制碳酸钙水垢。本规程适用于含10个以上的浓缩物流 000 mg/L的总溶解固体。对于含有少于10 000 mg/L的总溶解固体，参考实践 第1739页 。 1.2 以国际单位制表示的数值应视为标准。国际单位制后括号中给出的值仅供参考，不被视为标准值。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者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。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 在反渗透装置的设计和运行中，预测浓缩物流的碳酸钙结垢特性非常重要。由于浓缩物流中总溶解固体的增加以及钙离子、碳酸氢根离子和游离CO的盐通道的差异 2. ，浓缩物流的碳酸钙结垢特性通常与进料溶液的碳酸钙的结垢特性大不相同。这种做法允许根据给水分析和反渗透操作参数计算浓缩物流的S&DSI。 5.2 正的S&DSI表示形成碳酸钙水垢的趋势，这可能会损害反渗透性能。本规程给出了调整S&DSI的程序。

1.1 This practice covers the calculation and adjustment of the Stiff and Davis Stability Index (S & DSI) for the concentrate stream of a reverse osmosis device. This index is used to determine the need for calcium carbonate scale control in the operation and design of reverse osmosis installations. This practice is applicable for concentrate streams containing more than 10 000 mg/L of total dissolved solids. For concentrate streams containing less than 10 000 mg/L of total dissolved solids, refer to Practice D3739 . 1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after 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 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. 1.4 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 In the design and operation of reverse osmosis installations, it is important to predict the calcium carbonate scaling properties of the concentrate stream. Because of the increase in total dissolved solids in the concentrate stream and the differences in salt passages for calcium ion, bicarbonate ion, and free CO 2 , the calcium carbonate scaling properties of the concentrate stream will generally be quite different from those of the feed solution. This practice permits the calculation of the S & DSI for the concentrate stream from the feed water analyses and the reverse osmosis operating parameters. 5.2 A positive S & DSI indicates the tendency to form a calcium carbonate scale, which can be damaging to reverse osmosis performance. This practice gives procedures for the adjustment of the S & DSI.