The friction lengths are limited by the virtual anchor length, Lhot and Lcold.
The effective force of the fully restrained flowline and the friction force along a typical flowline can be illustrated in Figure 3‑1, where the red curve represents the Seff,res and the blue line represents the friction force along the flowline length.
The friction eventually intersects with the Seff,res at the point A and B for the hot end and cold end, respectively. The slope of the friction force is equal to μ·WPiP, i.e. the pipe / soil axial friction force per unit length. At the section between the points A and B (virtual anchors), the flowline expansion load is balanced by the friction force. Thus, the flowline of the section A-B is fully restrained, and there is no expansion in this section. This scenario is often referred as “long” flowline.
Another flowline expansion scenario is illustrated in Figure 4‑2, where the friction force does not intersect with the Seff,res, and the friction forces of the hot end and the cold end are balanced with each other. In this case, the entire “short” flowline is mobilized by expansion and there is no virtual anchor restricting the flowline growth.
4. FEATURES OF THE PROCEDURE
The major sections in the procedure include Data Input, Calculation, and Results Summary as detailed in the following sections.
4.2 Data Input
The required design data are directly input in this section. The following input is to be given:
- Pipeline Data: Pipeline length, type (single pipe or pipe-in-pipe), dimensions, material grade, coating data, etc.
- Operational Data: Operational temperature/pressure, content density, residual lay tension, etc.
- Soil Data: axial pipe/soil friction coefficient.
- Environmental Data: Water depth (profile), ambient temperature, Sea water density, etc.
4.3 Viewing Results
Effective forces and the flowline growth along the flowline are shown in Figure 4‑1 and Figure 4‑2 as examples.