AFT Blog
The process of sizing a pump for the application of priming a piping system as well as for normal operation is slightly more involved than if the system was already primed and the pump was to be sized for a liquid full system. For a system priming application, the intermediate elevations at high points in a piping system are relevant in regard to the pump that is used. If a pump is not able to generate enough head in order to overcome the high intermediate elevation points in a system, then the pump will provide no benefit to the system, even...
When evaluating the hydraulic behavior of aged pipelines and/or pipelines that are exposed to particularly corrosive or dirty fluids, building and running a hydraulic model is a great first step, but more engineering may be required. This is because, over time, residue in the pipeline fluid can buildup in the pipeline and essentially decrease the pipe inner diameter while increasing the roughness of the pipe’s inner surface. Corrosion can also change the roughness of the pipe’s inner surface. Engineers know that these changes due to buildup and corrosion in the pipes can significantly affect the hydraulics of the system, so while building a hydraulic model of the system is essential to evaluate its behavior, calibrating the model to account for these changes can be just as important in getting an accurate representation of your system. AFT Fathom and AFT Arrow offer a goal seeking module to assist with this calibration process with one data set of flow data. To understand how this can be done, visit Dylan’s blog. My blog here will take Dylan’s discussion one step further and discuss how AFT Fathom and AFT Arrow can be used to calibrate a hydraulic model with not just one but with multiple data sets using the GSC (Goal Seek and Control) module.
Previously, we talked about the Graph Guide and how to create Stacked Graphs. Another way to see the interactions between parameters is to show them on one graph with dual Y-axes and a common X-axis scale. I am going to again start with the AFT Impulse model, ‘Pump Startup With Event Transient.imp’, which is installed in the Examples folder, and use the ‘One Pump Start With One Running’ scenario. In the previous blog, we used a Stacked Graph to examine the pressures and flows at two valves (J6 and J9), which opened during the simulation. This time, we will put them...
Using graphs that are stacked on top of each other is a great way to see the variation of several parameters at once and how one interacts with the others. There are several ways to create stacked graphs using the new graphing features in AFT applications, which I will cover here. I am going to start with the AFT Impulse model, ‘Pump Startup With Event Transient.imp’, which is installed in the Examples folder. I am going to use the ‘One Pump Start With One Running’ scenario. We will first compare the flow and pressure in the pipe path from the Supply...
The primary way to view results when using Impulse is through graphical data. With the release of AFT Impulse 6, the power of the graphing features has been greatly increased. With this enhanced capability comes additional complexity. It is a kin to the power and complexity of in-dash radio consoles in modern cars compared to the old stereo in my old Ford Pinto. To help users navigate the new capabilities of this powerful graphing tool, we have developed a ‘Graph Guide’ which points out the steps to accomplish many of the common tasks in creating, modifying and keeping graphs. The Graph...
The majority of steady-state, incompressible hydraulic models made in AFT Fathom that we see as Applications engineers typically converge very rapidly. However, every once in a while, that occasional AFT Fathom model arrives in our Support inbox that just won’t converge. At first glance, passing a graduate level course in compressible flow without ever missing an exam question may seem more likely than getting to the source of the convergence issue in one of these typically-monstrous models (like in Figure 1), but the tips below show that determining and correcting the problem preventing convergence is frequently straightforward and much easier than...
You’ve built your AFT Fathom or AFT Arrow model, defined all pipes and junctions, specified your fluid properties and defined your pressure boundary conditions. But for some reason, your predicted flows are still not matching measured data. AFT Fathom or AFT Arrow is properly solving the fundamental equations, but it is likely that something is off in the inputted data. In many cases, this is the pipe’s resistance. Many factors can alter a pipe’s resistance, but the two primary reasons resistance may be incorrect is (1) corrosion of the pipe over time, which increases a pipe’s absolute roughness and (2) the buildup of residue on the walls of the pipeline, known as scaling, which decreases a pipe’s inner diameter. This decrease in diameter is very important and will increase a pipe’s resistance dramatically. Now you have a dilemma. You can’t cut open your pipe to see how much scaling there is or how much your pipe has corroded. What is the condition of your pipe? Using AFT Fathom GSC or AFT Arrow GSC, you can find out!