AFT xStream™

AFT xStream™ 2

Steam & Gas Transient Analysis Software

AFT xStream is a powerful fluid dynamic simulation tool for high-speed, acoustic transients that occur in steam and gas piping systems. Uncertainty in design and operations costs money and time. Now you can accurately simulate how your steam and gas systems will respond to potentially disruptive transient events.

Simulate and Solve Your Challenging Steam and Gas Transient Problems

  • Accurately simulate high-speed transients in steam and gas piping systems including choked flow conditions
  • Evaluate overall system response and transient pipe forces after steam and gas turbine trips
  • Predict transient supply pressures, temperatures and flows to operating gas compressors and turbines when one trips offline
  • Simulate tank blowdowns and charging, and how long it takes to reach desired pressures
  • Predict transient pressures and flows due to heat exchanger tube ruptures
  • Easily change system input data including transient valve positions, compressor operation, control set points, pressures, temperatures and more
  • Initiate transients based on time or events in the system

AFT xStream is designed for fluid systems containing the below fluids and more:


Compressed Air

Process Gases

Hydrogen & Natural Gas

Typical Applications
  • Ensure pressure, temperature and flow extremes are within design allowables
  • Determine imbalanced pipe forces for sizing structural supports
  • Troubleshoot existing systems to determine the cause of operational problems

How does it work

AFT xStream™ incorporates a highly accurate steady-state solver which provides seamless transfer of initial conditions to the transient analysis. Steady-state solutions are determined using a modified Newton-Raphson matrix iteration plus proprietary methods developed by AFT. A specialized Method of Characteristics is used to solve the transient mass, momentum and energy equations of pipe flow.

Primary Features of AFT xStream™ 2

  • Built-in steady-state solver to automatically initialize system before the transient
  • Automatic pipe sectioning based on steady-state acoustic velocities
  • Compound transient event logic to model complex control sequences
  • Scenario Manager to track all design variants and operational possibilities in a single model file
  • Integrated graphing and reporting
  • Animation tools for visual interpretation of complex transient interactions
  • Generates force imbalance files that can be automatically read into CAESAR II ®, ROHR2, AutoPIPE and TRIFLEX ® pipe stress dynamic models
  • 2D flow diagram or isometric view interface
  • Built-in libraries of fluids (including NIST REFPROP and ASME Steam Tables) and fittings which can be extended and customized
  • Chempak™ add-on utility provides a thermophysical database of almost 600 
  • gases – allows you to define non-reacting 
  • pre-mixtures and simulate dynamic flow mixing

Primary Features of AFT

Reporting Features

Modeling Features

AFT xStream Add-On Module

With this software extension tools, you can quickly and efficiently complete projects. Modules work within your existing AFT xStream models.

Pulsation Frequency Analys

Helps identify pipe acoustical frequencies to avoid resonance from excitation, especially in systems with reciprocating compressors.