MechEng901
Mechanical
- Apr 13, 2011
- 1
First post! and I have reviewed the existing forums with no prevail.
My concern is regarding combined circumferential stress calcs for a large diameter buried pipeline.
Minimum wall thickness calcs for pressure containment only have been carried out and comply with the allowable hoop stress limit of 72% (Location Class 1, Division 2) using standard wall thicknesses from API 5L.
There is now some lack of guidance in the ASME codes when considering external loading, there is a comment in the code(2010) that consideration must be taken for external loading and the total allowable circumferential stress (headed local stress) for this case is 90%SMYS.
However no guidance on the calcs, I have identified Marston loading equs, Sprangler and there is a technique with API 1102 (rail and highway crossings) for hoop stress under soil loading.
The problem is all these methods are providing vastly different results, the highest stresses produced using the technique within API 1102, but this results in numerous API 5L standard wall thickness upgrades being required.
Any guidance/experience with this would be appreciated.
Many Thanks,
MechEng901
My concern is regarding combined circumferential stress calcs for a large diameter buried pipeline.
Minimum wall thickness calcs for pressure containment only have been carried out and comply with the allowable hoop stress limit of 72% (Location Class 1, Division 2) using standard wall thicknesses from API 5L.
There is now some lack of guidance in the ASME codes when considering external loading, there is a comment in the code(2010) that consideration must be taken for external loading and the total allowable circumferential stress (headed local stress) for this case is 90%SMYS.
However no guidance on the calcs, I have identified Marston loading equs, Sprangler and there is a technique with API 1102 (rail and highway crossings) for hoop stress under soil loading.
The problem is all these methods are providing vastly different results, the highest stresses produced using the technique within API 1102, but this results in numerous API 5L standard wall thickness upgrades being required.
Any guidance/experience with this would be appreciated.
Many Thanks,
MechEng901
