1.1 该试验方法描述了两个基本等效的程序:一个是基于应力获得长期静水压强度类别，本文称为静水压设计基础（HDB）；另一个用于基于压力获得长期静水压强度类别（本文称为压力设计基础（PDB））。HDB基于材料的长期静水压强度（LTHS），PDB基于产品的长期静水压力- 强度（LTHS P ). HDB是一种材料属性，是通过评估由受试材料制成的测试管的应力断裂数据而获得的。PDB是一种特定于产品的属性，它不仅反映了制造产品的材料的属性，还反映了产品设计、几何形状和尺寸以及特定制造方法对产品强度的影响。PDB是通过评估压力破裂数据获得的。LTHS是通过分析压力与时间的关系来确定的- 破裂（即应力破裂）试验数据，涵盖不少于10000小时的试验期，并来自对受试材料制成的管道的持续压力试验。通过线性回归分析数据，得出最佳拟合的测井应力与测井失效时间的直线方程。使用该方程，通过外推法确定材料在100000小时截距（LTHS）下的平均强度。LTHS的合成值决定了材料所属的HDB强度类别。 LTHS P 类似地确定，除了该确定基于从特定产品导出的压力与时间数据。LTHS的分类价值 P 就是PDB。HDB/PDB是一系列优选的长期强度值之一。本试验方法适用于所有已知类型的热塑性管材和热塑性管道产品。它也适用于任何产生应力断裂数据的实际温度和介质，这些数据基本上呈直线- 当绘制在对数应力（每平方英寸磅力）或对数压力（每平方厘米磅力）与对数失效时间（小时）坐标上时，这种直线关系预计将持续至少100000小时。 1.2 除非实验获得的数据近似于直线，否则当使用对数坐标计算时，不可能为材料分配HDB/PDB。数据表现出高度分散或“膝盖”（向下移动，导致随后压力更陡）- 破裂斜率比早期数据所示的要低），但符合该测试方法的要求往往会给出较低的LTHS/LTHS预测 P 如果数据表现出过度分散或明显的“拐点”，则不符合本测试方法的置信下限要求，数据被归类为不适合分析。 1.3 该测试方法的一个基本前提是，当实验数据根据该测试方法要求定义了一条直线关系时，可以假设这条直线在实验期后持续至少100000小时（材料LTHS/LTHS的时间截距 P 已确定）。对于聚乙烯管道材料，该试验方法包括对该假设“验证”的补充要求。其他材料不包括此类验证要求（见 附注1 ). 因此，在所有这些其他情况下，由该测试方法的用户根据外部信息确定该测试方法是否符合材料长期健康安全/长期健康安全的预测 P 对于内部/外部环境和温度的每种特定组合。 注1: 对商用压力管道等级的聚氯乙烯（PVC）、聚丁烯（PB）和交联聚乙烯（PEX）材料获得的大量长期数据表明，这一假设适用于为这些材料的水和环境温度建立HDB。请参阅 附注2 和 附录X1 获取更多信息。 1.4 获得单个数据点的实验程序应如试验方法所述 D1598 ，这是该测试方法的一部分。当本试验方法的任何部分与试验方法不一致时 D1598 ，以本试验方法的规定为准。 1.5 本试验方法末尾包含一般参考文献。 1.6 本标准并不旨在解决与其使用相关的所有安全问题（如果有的话）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 1.7 以英寸-磅单位表示的值应被视为标准值。括号中给出的值仅供参考，不被视为标准。 注2: 塑料管道协会（PPI）的静水应力委员会对3000多组数据进行了分析，这些数据是通过用水、天然气和压缩空气测试的热塑性管道和管道组件获得的 2. PPI TR-4“PPI静水压设计基础（HDB）、静水压设计应力（HDS）、强度设计基础（SDB）、压力设计基础（PDB）和热塑性管道材料或管道的最低要求强度（MRS）等级清单”中目前商业上提供的化合物均未出现拐点- 在列出的温度下绘制类型图，即偏离直线，在等标量对数坐标系上绘制时，应力会在某个时间出现明显下降。在许多列出的材料上获得的环境温度应力断裂数据，其测试时间超过120000小时，没有显示出“膝盖”。但是，在一些不适合或不推荐用于管道化合物的热塑性化合物上获得的应力断裂数据被发现在23°C（73°F）时呈下降趋势，其中在该测试方法的最小测试时间10000小时之前出现了线性偏差。 在这些情况下，当采用这种测试方法进行分析时，获得的结果非常低，或者发现数据不适合外推。 通过PPI和其他方法对应力断裂数据的广泛评估也表明，在某些材料和某些测试条件下，通常在较高的测试温度下，在该测试方法所需的最低数据收集期10000小时之后，可能会出现线性偏差或“下降”。PPI研究表明，在聚乙烯管道材料预计会出现“下降”的情况下- 在73°F下10万小时之前，这些材料的长期现场性能比具有超出10万小时截距的预计“下降”的材料更容易出现问题。针对这些观察结果，1988年在该测试方法中增加了对PE材料的补充“验证”要求。本要求旨在拒绝使用本试验方法估算任何PE材料的长期强度，因为补充高温试验无法验证本试验方法的固有假设，即连续直线- 在23°C（73°F）下至少100000小时的线应力断裂行为。 当将此测试方法应用于其他材料时，应适当考虑以下可能性:对于所评估的特定等级的材料和特定的测试条件，特别是当涉及更高的测试温度和侵蚀性环境时，在数据收集期后的某个时间点可能会出现大幅“下降”。忽略这种可能性可能会导致该测试方法夸大材料的实际长期健康状况/长期健康状况 P 为了充分保证该测试方法的固有假设，即至少在100000小时内持续线性是适当的，用户应咨询并考虑该测试方法之外的信息，包括非常长期的测试或对类似材料的广泛现场经验。在无法充分保证实验数据所定义的直线行为的连续性的情况下，使用其他测试方法来预测长期- 应考虑术语强度（见 附录X1 ). 1.8 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====== 4.1 估算长期静水强度或压力的程序- 强度本质上是基于根据试验方法获得的数据，对应力-时间或压力-时间回归线的时间进行外推 D1598 .获得所选温度和环境的应力或压力破坏时间图:外推的方式是，在这些条件下估计长期静水压强度或压力强度。 注3: 试验温度最好从以下温度中选择:68°F（20°C）、73°F（23°C），140°F（60°C）和176°F（80°C）。 强烈建议在73°F（23°C）下生成数据以进行比较。 4.2 静水压或压力设计基础是通过考虑以下项目并根据以下标准进行评估来确定的 5.4 . 4.2.1 长期静水强度或100000小时的静水压力强度， 4.2.2 50年的长期静水强度或静水压力强度，以及 4.2.3 在100000小时时将产生5%膨胀的应力。 4.2.4 目的是考虑到基本压力- 材料的应变特性，因为它们与时间有关。 4.3 在一个温度下获得的结果不能确定地用于估计其他温度的值。因此，必须为每种特定种类和类型的塑料化合物以及每种温度确定静水压或压力设计基础。只要基于实验数据的计算值可用于感兴趣温度以上和以下的温度，就可以对特定温度下的材料长期强度进行估计。 4.4 静水压设计应力是通过将静水压设计基准值乘以使用（设计）系数获得的。 4.5 管道的压力额定值可以根据用于制造管道的特定材料的静水压设计应力（HDS）值及其尺寸，使用以下方程式计算 3.1.11 . 4.5.1 多层管道的压力额定值可以通过将压力设计基准（PDB）乘以适当的设计系数（DF）来计算。

1.1 This test method describes two essentially equivalent procedures: one for obtaining a long-term hydrostatic strength category based on stress, referred to herein as the hydrostatic design basis (HDB); and the other for obtaining a long-term hydrostatic strength category based on pressure, referred to herein as the pressure design basis (PDB). The HDB is based on the material's long-term hydrostatic strength (LTHS),and the PDB is based on the product's long-term hydrostatic pressure-strength (LTHS P ). The HDB is a material property and is obtained by evaluating stress rupture data derived from testing pipe made from the subject material. The PDB is a product specific property that reflects not only the properties of the material(s) from which the product is made, but also the influence on product strength by product design, geometry, and dimensions and by the specific method of manufacture. The PDB is obtained by evaluating pressure rupture data. The LTHS is determined by analyzing stress versus time-to-rupture (that is, stress-rupture) test data that cover a testing period of not less than 10 000 h and that are derived from sustained pressure testing of pipe made from the subject material. The data are analyzed by linear regression to yield a best-fit log-stress versus log time-to-fail straight-line equation. Using this equation, the material's mean strength at the 100 000-h intercept (LTHS) is determined by extrapolation. The resultant value of the LTHS determines the HDB strength category to which the material is assigned. The LTHS P is similarly determined except that the determination is based on pressure versus time data that are derived from a particular product. The categorized value of the LTHS P is the PDB. An HDB/PDB is one of a series of preferred long-term strength values. This test method is applicable to all known types of thermoplastic pipe materials and thermoplastic piping products. It is also applicable for any practical temperature and medium that yields stress-rupture data that exhibit an essentially straight-line relationship when plotted on log stress (pound-force per square inch) or log pressure (pound-force per square in. gage) versus log time-to-fail (hours) coordinates, and for which this straight-line relationship is expected to continue uninterrupted through at least 100 000 h. 1.2 Unless the experimentally obtained data approximate a straight line, when calculated using log-log coordinates, it is not possible to assign an HDB/PDB to the material. Data that exhibit high scatter or a “knee” (a downward shift, resulting in a subsequently steeper stress-rupture slope than indicated by the earlier data) but which meet the requirements of this test method tend to give a lower forecast of LTHS/LTHS P . In the case of data that exhibit excessive scatter or a pronounced “knee,” the lower confidence limit requirements of this test method are not met and the data are classified as unsuitable for analysis. 1.3 A fundamental premise of this test method is that when the experimental data define a straight-line relationship in accordance with this test method's requirements, this straight line may be assumed to continue beyond the experimental period, through at least 100 000 h (the time intercept at which the material's LTHS/LTHS P is determined). In the case of polyethylene piping materials, this test method includes a supplemental requirement for the “validating” of this assumption. No such validation requirements are included for other materials (see Note 1 ). Therefore, in all these other cases, it is up to the user of this test method to determine based on outside information whether this test method is satisfactory for the forecasting of a material's LTHS/LTHS P for each particular combination of internal/external environments and temperature. Note 1: Extensive long-term data that have been obtained on commercial pressure pipe grades of polyvinyl chloride (PVC), polybutylene (PB), and cross linked polyethylene (PEX) materials have shown that this assumption is appropriate for the establishing of HDB's for these materials for water and for ambient temperatures. Refer to Note 2 and Appendix X1 for additional information. 1.4 The experimental procedure to obtain individual data points shall be as described in Test Method D1598 , which forms a part of this test method. When any part of this test method is not in agreement with Test Method D1598 , the provisions of this test method shall prevail. 1.5 General references are included at the end of this test method. 1.6 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. 1.7 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only and are not considered the standard. Note 2: Over 3000 sets of data, obtained with thermoplastic pipe and piping assemblies tested with water, natural gas, and compressed air, have been analyzed by the Plastic Pipe Institute's (PPI) Hydrostatic Stress Board 2 . None of the currently commercially offered compounds included in PPI TR-4, “PPI Listing of Hydrostatic Design Basis (HDB), Hydrostatic Design Stress (HDS), Strength Design Basis (SDB), Pressure Design Basis (PDB) and Minimum Required Strength (MRS) Ratings for Thermoplastic Piping Materials or Pipe” exhibit knee-type plots at the listed temperature, that is, deviate from a straight line in such a manner that a marked drop occurs in stress at some time when plotted on equiscalar log-log coordinates. Ambient temperature stress-rupture data that have been obtained on a number of the listed materials and that extend for test periods over 120 000 h give no indication of “knees.” However, stress-rupture data which have been obtained on some thermoplastic compounds that are not suitable or recommended for piping compounds have been found to exhibit a downward trend at 23 °C (73 °F) in which the departure from linearity appears prior to this test method's minimum testing period of 10 000 h. In these cases, very low results are obtained or the data are found unsuitable for extrapolation when they are analyzed by this test method. Extensive evaluation of stress-rupture data by PPI and others has also indicated that in the case of some materials and under certain test conditions, generally at higher test temperatures, a departure from linearity, or “down-turn”, may occur beyond this test method's minimum required data collection period of 10 000 h. A PPI study has shown that in the case of polyethylene piping materials that are projected to exhibit a “down-turn” prior to 100 000 h at 73 °F, the long-term field performance of these materials is prone to more problems than in the case of materials which have a projected “down-turn” that lies beyond the 100 000-h intercept. In response to these observations, a supplemental “validation” requirement for PE materials has been added to this test method in 1988. This requirement is designed to reject the use of this test method for the estimating of the long-term strength of any PE material for which supplemental elevated temperature testing fails to validate this test method's inherent assumption of continuing straight-line stress-rupture behavior through at least 100 000 h at 23 °C (73 °F). When applying this test method to other materials, appropriate consideration should be given to the possibility that for the particular grade of material under evaluation and for the specific conditions of testing, particularly, when higher test temperatures and aggressive environments are involved, there may occur a substantial “down-turn” at some point beyond the data collection period. The ignoring of this possibility may lead to an overstatement by this test method of a material's actual LTHS/LTHS P . To obtain sufficient assurance that this test method's inherent assumption of continuing linearity through at least 100 000 h is appropriate, the user should consult and consider information outside this test method, including very long-term testing or extensive field experience with similar materials. In cases for which there is insufficient assurance of the continuance of the straight-line behavior that is defined by the experimental data, the use of other test methods for the forecasting of long-term strength should be considered (see Appendix X1 ). 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 ====== 4.1 The procedure for estimating long-term hydrostatic strength or pressure-strength is essentially an extrapolation with respect to time of a stress-time or pressure-time regression line based on data obtained in accordance with Test Method D1598 . Stress or pressure-failure time plots are obtained for the selected temperature and environment: the extrapolation is made in such a manner that the long-term hydrostatic strength or pressure strengthis estimated for these conditions. Note 3: Test temperatures should preferably be selected from the following: 68 °F (20 °C), 73 °F (23 °C), 140 °F (60 °C), 176 °F (80 °C), 180 °F (82 °C), and 200 °F (93 °C). It is strongly recommended that data be generated at 73 °F (23 °C) for comparative purposes. 4.2 The hydrostatic or pressure design basis is determined by considering the following items and evaluating them in accordance with 5.4 . 4.2.1 Long-term hydrostatic strength or hydrostatic pressure-strength at 100 000 h, 4.2.2 Long-term hydrostatic strength or hydrostatic pressure-strength at 50 years, and 4.2.3 Stress that will give 5 % expansion at 100 000 h. 4.2.4 The intent is to make allowance for the basic stress-strain characteristics of the material, as they relate to time. 4.3 Results obtained at one temperature cannot, with any certainty, be used to estimate values for other temperatures. Therefore, it is essential that hydrostatic or pressure design bases be determined for each specific kind and type of plastic compound and each temperature. Estimates of long-term strengths of materials can be made for a specific temperature provided that calculated values, based on experimental data, are available for temperatures both above and below the temperature of interest. 4.4 Hydrostatic design stresses are obtained by multiplying the hydrostatic design basis values by a service (design) factor. 4.5 Pressure ratings for pipe may be calculated from the hydrostatic design stress (HDS) value for the specific material used to make the pipe, and its dimensions using the equations in 3.1.11 . 4.5.1 Pressure ratings for multilayer pipe may be calculated by multiplying the pressure design basis (PDB) by the appropriate design factor (DF).