Strength and leak tests of newly constructed or modified pipeline sections or piping assemblies are required by code. This is often conducted by pressurizing incompressible medium, such as water, water-methanol or water-propylene glycol (PG) mixtures while the system is sealed. Major challenges are invariably encountered with leak tests, which rely on correlating changes in the test pressure to the test fluid temperature (DP/DT) to discern if a leak exists. Often, the temperature variations are never correlated to pressure variations for several reasons: 1) access to the test fluid temperature is not available for several reasons outlined in the paper, therefore, the measured external pipe wall temperature is taken instead and is assumed to be equal to the test fluid inside the pipe, 2) the pipe wall temperature variations are generally significant due to variation in the ambient temperature or wind speed (in the case of exposed pipe), 3) the pipe section may not be restrained from axial movement, 4) tables and calculations of DP/DT are readily available for pure water and often erroneously assumed to be applicable to other test media such as mixtures of water-methanol or water-PG, which are vastly different than pure water, and 5) some pipe sections may be partially exposed to ambient and partially buried. The present work addresses these factors via development of high-fidelity models based on governing equations that accounts for the respective effects in a more fundamental manner. It was found that it is paramount to use the correct test medium isothermal bulk modulus and its coefficient of volumetric thermal expansion at the test conditions as these two parameters have the most significant influence on DP/DT. Due to these properties, water-PG was shown to result in the highest DP/DT, which poses the greatest challenges during hydrotesting in the field. Additionally, it was found that the difference between the pipe external wall temperature and the test fluid average temperature for the case of exposed pipe increases as Biot number increases. The developed thermal transient models were compared to three field hydrotests of different pipe sizes, namely DN900, DN150 and DN50, all above ground subject to cross wind and variations in ambient air temperatures.

规范要求对新建或改建的管道部分或管道组件进行强度和泄漏测试。这通常是通过在密封系统的同时对不可压缩的介质（例如水，水-甲醇或水-丙二醇（PG）混合物）加压来进行的。泄漏测试始终面临主要挑战，这取决于将测试压力的变化与测试流体温度相关联（DP / DT）以识别是否存在泄漏。通常，由于以下几个原因，温度变化永远不会与压力变化相关：1）由于本文概述的几个原因，无法获得测试流体温度，因此，取而代之的是测得的外部管道壁温，并假定为等于管道内的测试流体; 2）由于环境温度或风速的变化（在裸露的管道中），管道壁温变化通常很明显; 3）管道截面可能不受轴向移动的限制，4）DP / DT的表格和计算容易获得纯净水，并且经常错误地假定适用于其他测试介质，例如与纯净水有很大不同的水-甲醇或水-PG的混合物，以及5）一些管道段可能会部分暴露于环境和部分埋葬。本工作通过基于控制方程的高保真模型的开发来解决这些因素，该方程以更基本的方式解释了各自的影响。发现在试验条件下使用正确的试验介质等温体积模量及其体积热膨胀系数是至关重要的，因为这两个参数对DP / DT的影响最大。由于这些特性，水-PG表现出最高的DP / DT，这在现场水力测试中提出了最大的挑战。另外，发现对于暴露的管道，管道外壁温度和测试流体平均温度之间的差异随着Biot数的增加而增加。将开发的热瞬态模型与三种不同管道尺寸的现场水压试验（即DN900，DN150和DN50）进行了比较，这些试验均在地面以上，受到侧风和环境空气温度的变化的影响。