Page 513 - Pipelines and Risers

480 Chapter 25

The calculation of the allowable collapse pressure is based on the parameters given in Table
25.2.
Tabk 25.2 Functional Moments and Force.
PARAMETER I VALUE I REFERENCE
M. I 0.6 MPa I ~relimin~ in-dace analvsis

The operational data presented in Table 25.3 has been used. The temperature drop in the
bundle is estimated, based on calculated temperature profiles, an inlet temperature of 7OoC,
and a bundle length of 400 m.
Table 253 Operational Data.

II PARAMETER I UNIT I VALUE 1
Design Pressure Bar 225
Temperature @ end bundlel "C 45
start pipeline
COP content

2. DefectLength
Intelligent pig inspections from the Emden gas pipeline show defect sizes after approx. 20
years of service which can be illustrated by the distribution function shown in Figure 25.1.
(Nodland, Bai and Damsleth, 1998). This function has been used to describe the expected
defect length in the line.

It should be noted that the defects in the Emden line have occurred following a history of
operational difficulties. After these have been sorted out, the defect growth and occurrences of
new defects have decreased significantly.

3. Wall Thickness Uncertainty
In this calculation example the parameter which is being investigated is the fabrication quality
of the pipeline. As additional complexity would be introduced into the limit state equations it
has been chosen to represent this difference in fabrication quality through the wall thickness
uncertainty variable. This parameter is represented by the following.