Page 35 - Pipelines and Risers

Introducfion 9

In order to efficiently conduct DTA, it is necessary to develop a Pipeline Simulator System
(see Chapter 1.5).

1.4 Pipeline Design Analysis

1.4.1 General
Pipeline stress analysis is performed to determine if the pipeline stresses are acceptable (in
accordance with code requirements and client requirements) during pipeline installation,
testing and operation. The analysis performed to verify that stresses experienced are
acceptable include:

- Hoopstress;
- Longitudinal stress; code specified
- Equivalent stress;
- Span analysis and vortex shedding;
- Stability analysis;
- Expansion analysis (tie-in design);
- Buckling analysis;
- Crossing analysis.

The first three design stages form the basis for the initial wall thickness sizing. These initial
sizing calculations should also be performed in conjunction with the hydrostatic
collapse/propagation buckling calculations from the installation analysis.

The methods of analyses are briefly discussed below, as an introduction to separate chapters.

1.4.2 Pipeline Stress Checks
0 HoopStress
Hoop stress (cQ,) can be determined using the equation (see also Figure 1.4):

where:
pi = internal pressure
pe = external pressure
D = outside diameter of pipeline
t = minimum wall thickness of pipeline
Depending on which codektandard, the hoop stress should not exceed a certain fraction of thc
Specified Minimum Yield Stress (SMYS).