Applies To | |

Product(s): | AutoPIPE |

Version(s): | ALL; |

Environment: | N/A |

Area: | Modeling |

Original Author: | Bentley Technical Support Group |

Date Logged& Current Version | Dec. 201610.01.00.09 |

Does AutoPIPE consider external pressure or temperature for underwater / subsea piping?

First ask yourself, what piping code and year was selected to analyze the model? Does that selected piping code consider external Pressure? Answer, most ASME codes do not, however DNV does calculate that effect. In general, AutoPIPE adheres to the code calculations mentioned in the selected piping code and year selection (see AutoPIPE help for these detail calculations).

However, the external pressure can be approximately accounted for by subtracting it from internal pressure, and the external temperature can be approximated finding the average pipe temperature using heat transfer concepts. Otherwise use bounding values, like higher and lower temperatures as two separate load-cases.

AutoPIPE pressure extension analysis takes in to account the Poisson’s ratio affect due to internal pressure. The Poisson ratio effects due to external pressure may be approximated by setting the internal pressure as net pressure i.e. set internal pressure = Pi – Pe, where Pi is actual internal pressure and Pe is the external pressure on pipe.

See AutoPIPE FAQ#36: How do I calculate the DNV 2000 tension terms.

**Model Subsea (Underwater) Piping**