<p>Strength and leak tests of newly constructed (or modified) pipelines and piping segments are required by code. Testing is often completed by pressurizing incompressible fluids (such as water, water-methanol or water-glycol mixtures) and monitoring the sealed pressure over time. However, when it comes to fully or partially exposed pipe leak tests, challenges are invariably encountered by virtue of several effects which are often unaccounted for. For example, temperature measurements at the pipe's external wall are generally assumed to be the same as that of the test fluid, and the effects of cross wind and ambient temperature variations are often neglected.&nbsp; Other influencing parameters such as the pipe restraint condition, and radial and axial variations in the fluid temperature are difficult to discern due to the limited number of measurement locations. To help bridge the gap with respect to a few of these effects, the present work demonstrates the use of integral transforms as a means for analytically solving the non-homogeneous 1D transient equations describing the temperature distribution of the test fluid in a cylindrical pipe. Specifically, the solution produced can accommodate the influence of non-homogeneous initial conditions (i.e., as a function of the radius) and the effects of ambient temperatures which can vary over the duration of the leak test. Furthermore, the analytical solution enables for a direct understanding and exploration of the functionality existing between the average fluid temperature (as well as the wall temperature) and several dimensionless groups (i.e., the Biot number and dimensionless time). Additionally, the analytical solution results are also shown to be in excellent agreement with those of a numerical scheme used previously to solve the problem. Furthermore, given the explicit nature of the analytical expression an eigenvalue optimization was completed, and the lowest number of terms required to provide a converged description of the average temperature was identified. As a final validation, the methodology developed was employed to estimate the average fluid temperature during a 4-hour hydro/leak test in the field involving a DN900 pipe segment with a wall thickness of 22.5 mm. The average temperature estimated (as a function of the variations in the temperature of the surrounding air) was then used to compute the corresponding pressure change (i.e., accommodating for the pipe's thermal expansion, the isothermal bulk modulus and the volumetric thermal expansion coefficient of the test fluid). Good agreement was observed between the predicted and measured pressure data during the test. From the results of this work, it can be noted that the external pipe wall temperature often differs from the average temperature of the fluid, which is the critical parameter required to estimate pressure changes and accurately discern leaks and accept/reject test results. Overall, the use of the analytical solution presented should help improve the accuracy and speed of leak discernment in hydrotesting applications.</p>

Innovation in Hydrotesting Above Ground Pipes: Analytical Solution via Integral Transforms for Discerning Test Fluid Temperatures Subject to Ambient Temperature Variations

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.