Pipeline Expansion Analyses

[pipelinermike]

A pipeline is installed in 3300 ft water depths (1467 psi external pressure) in a void state, i.e. internal pressure is zero. The pipeline is unburied - laying on bottom and there is a riser to the surface on one end.

The following have been proposed:

1. Pressure expansion (end cap, Bourdon, etc) occurs only when the internal pressure exceeds the external pressure. When the internal pressure is less than ambient, e.g.
during flooding or filling, the pipeline would contract as described by the Poisson effect.

2. Pressure expansion occurs at any point from the initial, void state. The hoop stress, and consequently
equivalent stress, would have to be re-calculated to account for the external pressure.

This is a most critical decision for us, therefore please include references to any text, papers, etc. with your reply if you have them.

 

[jfduroch]

As far as I am concerned Regardless of the fact whether the pipe is empty of filled, the pressure components of the axial force Shall be accounted in the calculation for expansion. Please refer to DnV OS F101 that will provide you with the fully constraint axial force formula for your pipe. As It is buried, I suspect that Expansion and/or contraction will not be much IE you pipe will be very quickly fully constraint.
What is in fact your question ?
- do you want to calculate expansion/contraction ?
- do you want to check pipe axial constraint ?
please be more specific.

 

[sabaii]

Hi pipelinermike,
First and foremost, when you are looking at the expansion, you need to bear in mind with regard to your reference point. If you are looking from the vessel point of view, then expansion/contraction will take place due to the pressure of the water depth.