Does AutoPIPE consider external pressure or temperature for underwater / subsea piping?
AutoPIPE does not consider external pressure or temperature. However, the external pressure can be approximately accounted for by subtracting it from internal pressure. External temperature can be approximated finding the average pipe temperature using heat transfer concepts. Other wise 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