JPE - Sept09 - cover2-4.pmd - Pipes & Pipelines International ...

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Background on case study
The Camisea system consists of a buried natural gas (NG)
pipeline and a buried natural gas liquid (NGL) pipeline.
The NGL pipeline transports liquid condensates from
Malvinas in the Peruvian Amazon to a fractionation plant
near Pisco, on the coast of Peru south of Lima (see Fig.1).
The pipeline starts in the jungle (“selva”) and climbs up the
east slopes of the Andes Mountains (“sierra”) to a height of
approximately 4,800m, from where it drops steeply towards
the coastal (“costa”) city of Pisco. The NGL pipeline is
approximately 561km long, and telescopes from a nominal
pipe diameter of 14 to 10.75in. The wall thickness of the
NGL pipeline ranges between 0.219 and 0.469in. The 734km
long and larger-diameter NG pipeline shares the same
right-of-way (RoW) along its initial 550km until it follows
the Pacific coast towards Lima. Both pipelines are
constructed of tubular high-strength steel (X70) in
conformance with the American Petroleum Institute (API)
5L standard, welded and inspected per API 1104, and
The Journal of Pipeline Engineering
Mountains, the Camisea transportation system, which is buried in a region where landslides and other
geological hazards are common.
In this paper an elastic plastic fracture mechanics analysis of a pipeline is presented that ruptured due to
external soil loading, to evaluate possible loading conditions and correlate the observed crack propagation
with possible external loading conditions. Next a fracture mechanics based performance criterion is derived
for the most commonly used in-line inspection (ILI) methods, to detect these circumferential cracks; i.e.
the magnetic flux leakage (MFL) tool.
Fig.1. Alignment of the NGL and NG pipeline of the Camisea system in Peru [5].
protected by a triple layer of polyethylene. All girth welds
were x-rayed 24hrs after welding and evaluated per API
1104 [5, 6].
Since the Camisea Transportation System was brought
into service in August, 2004, the NGL pipeline has
experienced six spill incidents involving a release of NGL;
however, no incident has been reported for the NG pipeline
(see Fig.1). Three of these failures occurred at girth welds
and were determined to result from soil loading due to
ground movement [5]. Overall the Camisea pipeline system
has experienced a spill incident rate of approximately 1.1
spill incidents 2 per 1000 km year, which is slightly larger
than the spill incident rate of contemporary South American
pipelines through similar regions that were constructed
with the newest geotechnical means. However, the spill
incident rate of the Camisea system should improve because
2 Using the combined length of the NG and NGL pipeline.
Sample issue