Mathematical model of pressure distribution in a main pipeline during pumping with the use of drug reducing agents, taking into account their degradation

Путевая деградация противотурбулентных присадок (ПТП) может стать причиной изменения основных параметров режима магистрального трубопровода - давления и расхода - относительно установившихся значений и осложнить контроль их отклонений от нормативных показателей. При этом до настоящего момента отсутствовала методика расчета режимов перекачки при использовании ПТП с учетом деградации. Авторами была поставлена цель по разработке методики для математического описания распределения давления в трубопроводе с учетом путевой деградации присадки, а также при различных концентрациях ПТП. Для достижения указанной цели предлагается дополнить уравнение баланса напоров с учетом эмпирической зависимости эффективности присадки от длины трубопровода. При расчетах давления в промежуточных точках трассы предлагается использовать данные опытно-промышленных испытаний по изменению эффективности ПТП. Для иллюстрации применения методики рассматриваются примеры перекачки нефти и нефтепродуктов с добавлением присадок в различных концентрациях. На основании экспериментальных данных получена адекватная математическая модель снижения эффективности ПТП по длине магистрального трубопровода для различных концентраций вводимой присадки. Path degradation of drug reducing agents (DRA) can cause changes in the main mode parameters of the main pipeline; pressure and flow rate, relative to the stable values, and complicate the adjustment of their deviations from the standard indicators. At the same time, up until now there has been no methodology for calculating pumping modes when using DRA that takes degradation into account. The authors set a goal to develop a methodology to mathematically describe the pressure distribution in the pipeline, taking into account the path degradation of the agent, as well as the parameters at different DRA concentrations. To achieve this goal, it is proposed to supplement the equation of the pressure head balance with the empirical dependency of agent efficiency on the length of the pipeline. When calculating the pressure at intermediate points of the route, it is proposed to use the pilot run data on the change in the DRA efficiency. To illustrate the application of the methodology, examples of pumping oil and petroleum products with added agents in various concentrations are discussed. On the basis of the experimental data, an adequate mathematical model of the DRA efficiency reduction along the length of the main pipeline for different concentrations of introduced agent was obtained.

How not to run out of oxygen: Primary FRCA forcibly put into practice by COVID-19 to maintain patient safety

Background SARS-CoV-2 is currently the cause of a global pandemic, putting significant strain on healthcare systems worldwide. Reports reaching the United Kingdom, ahead of the pandemic, and previous surge planning (H1N1 influenza) highlighted that pipeline oxygen supply could be strained. Therefore, this study was created to investigate the robustness of pipeline oxygen supply at Darent Valley Hospital. Coinciding news reports of hospitals declaring major incidents, due to oxygen failure, further backed the contingency planning. Methods The maximum sustainable flow from the vacuum insulated evaporator (VIE) was calculated, followed by a snapshot survey identifying the exact usage of oxygen (litres per minute) across the entire hospital, also highlighting areas of high demand. A flowchart protocol was created for clinicians and engineers to follow should pipeline pressure drop. Finally, a second audit, monitoring oxygen usage and pipeline pressure, throughout the surge period, was undertaken. Results The initial survey found a usage of 412.15 L/min, which increased to 1789 L/min during the surge, with the lowest pressure recorded at 3.6 bar. The output from the VIE plant was managed through cycling of its evaporators every 12 h, to prevent pipeline freezing. Conclusions Data and contingency planning ensured maintenance of pipeline pressure throughout a pandemic surge of 576 COVID-19 patients. It also served as the foundation of a business case that resulted in, planning, approval, and installation of a second VIE plant in four weeks, ensuring readiness for further surge activity and future pandemics.

Power Spectral Density Analysis of Pipeline Pressures for Probabilistic Assessment

Pipeline pressure-cycle fatigue analysis is typically performed by analyzing pressure data in the amplitude domain and then calculating incremental fatigue crack growth in accordance with the Paris Law. Alternatively, the stochastic pressure history is converted to an equivalent number of uniform-amplitude cycles using a cumulative damage rule. The fatigue life may then be estimated by integration of the Paris Law. This second approach is computationally less involved and therefore lends itself to a probabilistic analysis because of the large number of iterations necessary with techniques such as Monte Carlo analysis. However, studies have shown that for a broadband stochastic signal, applying linear cumulative damage can introduce large errors. The presence and magnitude of error cannot be easily determined by inspection of the pressure signal. This paper describes the analysis of the pipeline pressure signal in the frequency domain to determine the power spectral density. The result can be used to estimate correction factors to the estimated linear cumulative damage fraction. The corrections may then be applied with a simplified integration of the Paris Law in closed form to improve both accuracy and speed for probabilistic assessment. The computation time for a probabilistic assessment may potentially be reduced by a significant factor.