A common misunderstanding is the interpretation of parameters (16) and (17) in AutoPIPE Vessel reports.
Key Clarification
Parameters (16) and (17) are NOT caused by pressure thrust.
They represent membrane stresses due to internal pressure, calculated independently of the Pressure Thrust option.
Meaning of APV Report Parameters
|
Parameter |
Description |
|
Radial Load |
P = [FR] + [PT] |
|
[FR] |
Radial Load (user input) |
|
[PT] |
Pressure Thrust = Ps × π(ro-t)2 |
|
(16) |
Longitudinal (axial) stress in the nozzle neck due to internal pressure (ASME UG‑27) |
|
(17) |
Circumferential (hoop) stress in the nozzle neck due to internal pressure (ASME UG‑27) |
|
(22) |
Longitudinal stress in the shell due to internal pressure (UG‑27) |
|
(23) |
Circumferential stress in the shell due to internal pressure (UG‑27) |
These stresses exist even when no external nozzle loads are applied.
Effect of Pressure Thrust Option
Turning the Pressure Thrust option:
-
- ✅ Does NOT change parameters (16) or (17)
- ✅ Adds an axial force component to nozzle load equilibrium
- ✅ Affects WRC load-based stresses, not pressure membrane stresses
This behaviour is intentional and verified, and matches AutoPIPE Vessel’s design philosophy.
See Also