 ### Equation for calculating collapse pressure of the subsea pipeline?

Can anyone please help with equation for calculating the collapse of the subsea pipeline due to external pressure?

0
4 years, 8 months ago

A buckle resulting from excessive bending or another cause may propagate (“travel” along the pipeline). Offshore hydrocarbon pipelines can fail by a propagating buckle caused by the hydrostatic pressure of the surrounding seawater on a pipeline with a diameter-to-wall-thickness ratio that is too high.

The minimum wall thickness, which will prevent the formation of propagating buckles, can be calculated as follows: Note: Buckle arrestors should be used if the minimum wall thickness does not satisfy above conditions.

0
4 years, 8 months ago

The pipeline can also see buckling due to combined bending and external pressure. Combined bending strain and external pressure load should satisfy in accordance with API-1111 as follows: To avoid buckling, bending strains should be limited as follows: Where: Note: A typical conservative value of 2.0 often used for safety factors f1

0
4 years, 8 months ago

The collapse pressure of the pipe must exceed the net external pressure everywhere along the pipeline in accordance with API-1111 as follows:  Where:

Pi = Internal Pressure

Po= External hydrostatic pressure

Pe = elastic collapse pressure of the pipe, in psi

Py = yield pressure at collapse, in psi

f0= Collapse factor (A 0.70 Collapse factor is required for seamless or ERW pipe)

E = modulus of elasticity, in psi

v = Poisson’s ratio (0.3 for steel)

t = Pipe thickness

D = Pipe outside diameter