| Applies To | |
| Product(s): | AutoPIPE |
| Version(s): | ALL; |
| Area: | Results |
| Date Logged & Current Version | Feb. 2019 12.00.00.14 |
Problem:
Pressure consideration for DNV limits (as both internal and external pressure considered) v/s stress design “ASDC” (only internal pressure considered as differential) in AutoPIPE?
Solution:
It’s right that both internal and external pressure are considered for DNV limits such as calculation of internal/external overpressure of local buckling category. Where,
> Internal pressure, Pi = Pressure defined on Operating pressure & Temperature dialog
> External pressure, Pe = Pressure based on depth (No direct input)
> Min Pressure, Pmin= Minimum internal pressure, normally taken as zero for laid pipeline as per code
However, for stress design “ASDC” category AutoPIPE considers internal pressure for pressure extension analysis. In order to consider the external pressure, internal pressure can be set as an approximation as the differential of internal and external pressure. This is documented in program help page “Allowable Stress Design Check (DNV-2012)” note3: