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Modeling Effects of System Wear

Posted in AFT Fathom, AFT Arrow, AFT Titan, AFT Impulse, AFT Mercury

AFT modeling software offers a variety of ways to analyze the effects of wear and aging on a piping system.

  • Model increased effective wall roughness due to scaling or corrosion by specifying a corresponding roughness factor. You can do this directly within the Pipe Specifications window by selecting 'Unspecified' in the 'Friction Model Data Set' area of the 'Pipe Model' tab then entering the specific roughness value to be used. Alternatively, you may set up alternate 'friction data sets' within the Pipe Material Database with descriptive names (e.g. "10 year old pipe") and then simply select them within the Pipe Specifications windows from the drop down list in the 'Friction Model Data Set' area of the 'Pipe Model' tab.
  • Heavy scaling reducing the effective pipe ID can be reflected by specifying a 'Scaling Factor' on the 'Optional' tab of the Pipe Specifications window (which you may want to use in conjunction with increased wall roughness).
  • Applying 'Design Factors' to pipe or junction friction losses or to pump performance, specified on the 'Optional' tab of pipe and junctions specifications windows. To model increased pressure drop for pipes and junction losses you'll specify a value greater than 1.0 (e.g. 1.20 means the calculated pressure drop will be increased by 20% in the analysis). Conversely, modeling pump or compressor performance degradation requires specifying a value less than 1.0 (e.g. for a value of 0.9, 90% of the pump or compressor/fan curve head will be used).

This is a great place to be using Scenario Manager where a child scenario can be made from the 'new' system model and the 'aging' factors applied. As you investigate varying design parameters (e.g. different pipes sizes, valve Cv's, etc.), make changes in the 'new' system scenario and they will be automatically reflected in the lower, 'aged' system model scenario.

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