AFT Blog

Welcome to the Applied Flow Technology Blog where you will find the latest news and training on how to use AFT Fathom, AFT Arrow, AFT Impulse, AFT xStream and other AFT software products.

World Languages and Waterhammer

The demand for our AFT Impulse waterhammer modeling software and associated training seminars has been growing steeply in recent years. I frequently travel internationally to teach  seminars on waterhammer. When I do I make it a point to find out what the engineer's local language calls waterhammer.

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How AFT Impulse Can Help Engineers Comply With ASME Codes

Summary Engineers are often responsible to design systems to comply with codes and standards. In recent years codes that apply to waterhammer and surge pressures have become more prominent. Increasingly AFT Impulse is being used to help engineers comply with such codes. Once AFT Impulse has calculated the maximum pressure due to a transient event, what shall the designer do with this value? The answer to this question depends on the code that is being used as the piping design basis. In this article, we’ll be discussing how two important piping design codes - B31.4 and B31.3 - deal with surge...

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May the Force Be With You: Evaluating Unbalanced Forces Caused by Waterhammer

A common task among pipe stress engineers is to evaluate loads on pipe systems caused by waterhammer. Since AFT Impulse 4.0 was released our users have had the ability to calculate waterhammer-induced unbalanced forces for use in any pipe stress analysis application. In addition, our users can create specially formatted transfer files for direct use in CAESAR II and TRIFLEX. However, the process of calculating such forces in AFT Impulse and then applying them in pipe stress software is not as straightforward as it sounds. Our customers have asked for assistance in this process. I have teamed with AFT's distributor in Canada...

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Multi Scenario Output

Viewing the output from multiple scenarios in the same window can be a valuable and time saving tool! You must have output available for each of the scenarios you would like review. One way to do this is by executing a batch run: Select “Start Batch Run…” from the file menu.Click “Add Scenarios” and select which scenarios you would like to include in your multi-scenario output.Click “Start Run” and sit back while each of the scenarios is run. In order to view output from multiple scenarios in the same window, follow these steps: Browse to the Output window of one of...

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How to Fill as Quadratic

Filters and screens impose a pressure drop that varies with flow rate. The variation is non-linear, but manufacturers will often provide only one data point for pressure loss at the design flow rate. Using a single point, or constant pressure drop, can produce significant inaccuracies in your model. With this in mind, AFT offers the “Fill As Quadratic” option for entering loss data. Using only a single point, “Fill As Quadratic” will create two additional points for you. This first is simply 0,0; zero flow produces zero pressure drop. The second point is 2 x Flow and 4 x Pressure Drop....

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Jumping From Pipe to Pipe or Junction to Junction

You can jump from junction to junction or from pipe to pipe by pressing F5 while in a specifications window.

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Problems With Heat Exchanger Specified Heat Rate In Constants?

Using “Specified Heat Rate In Constants” for the thermal model of heat exchangers can often cause problems in system models.  The reason why is because this thermal model type causes the heat exchanger to act like an “assigned heat input” junction as does an assigned flow junction does for providing constant flow rates.  Another problem is that this thermal model can cause unrealistic temperature changes across a heat exchanger.  When the heat rate is specified and the mass flow rate and heat capacity are calculated based on the system solution, the temperature change will be whatever is required to maintain the...

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