Page 201 - Pipelines and Risers
P. 201
174 Chapter 11
As long as the pullover load used as input to the analysis is a strong function of the gap
height, other variables such as span length and axial force in the 10-inch flowline prior to
impact, did not significantly affect the response.
The pullover loads and durations, based on Eqs. (1 1.19) to (1 1.26) for a 10-inch flowline, are
presented in Figure 11.7 below.
Among others, the following parameters influence the pullover loads:
Flexibility, which is governed by pipeline diameter, wall-thickness, span length and
supporting condition.
Geometrical effects, for instance due to the relative position and motion between the trawl
gear and the pipeline, front geometrical shape of trawl gear and the location where wire
rope is attached. See Figure 11.8.
Trawl pull-over loads
Span height
Figure 11.7 Pullover loads and duration for different span heights.
Figure 11.8 Geometrical effect on pull-over loads for pipelines on seabed and on a free-spanning pipeline.