1.1 本规程涵盖所有基于石油、合成或天然基础油的液压油。它不适用于含有液压油的水。 1.2 在低温下测定粘度时，本规程使用毫帕秒（mPa·s）作为粘度单位。供参考，1 mPa·s相当于1厘泊（cP）。在高温下测定粘度时，本规程使用毫米平方/秒（mm 2. /s） 作为运动粘度的单位。供参考，1 毫米 2. /s相当于1厘斯托克（cSt）。 1.3 本规程适用于运动粘度约为4的流体 毫米 2. /s至150 毫米 2. /s，在40的参考温度下测量 °C和以下温度 −50 °C至 +16 液体粘度为750°C mPa·s。 注1: 粘度小于或大于中所述范围的流体 1.3 很少用作液压油。将系统的任何数学外推到更高或更低的粘度等级可能不合适。任何扩大该系统的需要都应根据其本身的优点进行评估。 1.4 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。 1.5 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 本规程的目的是建立由试验方法测量的粘度得出的粘度名称，该粘度与液压流体性能有重要关系。这使得润滑油供应商、润滑油用户和设备设计师在指定、指定或选择液压油粘度特性方面具有统一和通用的基础。 5.2 本规程不旨在取代分类 D2422 . 相反，它是一种增强，旨在更好地描述用作液压油的润滑剂的粘度特性。 5.3 该实践表明，除了在规定条件下的粘度和剪切稳定性外，不评估液压油质量。 5.4 虽然本规程不适用于其他功能流体，但在使用粘度指数（VI）改进剂来扩大流体有效工作温度范围的高剪切应力应用中，本规程可能有用。 5.5 本规程不适用于已经存在粘度分类系统的其他润滑剂，例如，SAE J300适用于汽车发动机机油，SAE J306适用于轮轴和手动变速器润滑剂。

1.1 This practice covers all hydraulic fluids based either on petroleum, synthetic, or naturally-occurring base stocks. It is not intended for water-containing hydraulic fluids. 1.2 For determination of viscosities at low temperature, this practice uses millipascal·second (mPa·s) as the unit of viscosity. For reference, 1 mPa·s is equivalent to 1 centipoise (cP). For determination of viscosities at high temperature, this practice uses millimetre squared per second (mm 2 /s) as the unit of kinematic viscosity. For reference, 1 mm 2 /s is equivalent to 1 centistoke (cSt). 1.3 This practice is applicable to fluids ranging in kinematic viscosity from about 4 mm 2 /s to 150 mm 2 /s as measured at a reference temperature of 40 °C and to temperatures from −50 °C to +16 °C for a fluid viscosity of 750 mPa·s. Note 1: Fluids of lesser or greater viscosity than the range described in 1.3 are seldom used as hydraulic fluids. Any mathematical extrapolation of the system to either higher or lower viscosity grades may not be appropriate. Any need to expand the system should be evaluated on its own merit. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 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 The purpose of this practice is to establish viscosity designations derived from viscosities measured by test methods which have a meaningful relationship to hydraulic fluid performance. This permits lubricant suppliers, lubricant users, and equipment designers to have a uniform and common basis for designating, specifying, or selecting the viscosity characteristics of hydraulic fluids. 5.2 This practice is not intended to be a replacement for Classification D2422 . Rather, it is an enhancement intended to provide a better description of the viscosity characteristics of lubricants used as hydraulic fluids. 5.3 This practice implies no evaluation of hydraulic oil quality other than its viscosity and shear stability under the conditions specified. 5.4 While it is not intended for other functional fluids, this practice may be useful in high-shear-stress applications where viscosity index (VI) improvers are used to extend the useful operating temperature range of the fluid. 5.5 This practice does not apply to other lubricants for which viscosity classification systems already exist, for example, SAE J300 for automotive engine oils and SAE J306 for axle and manual transmission lubricants.