Pipeline integrity audit – Camisea Project

Patricia Rojas

Informations

• Publié par: Feduh
• Nombre de lectures: 23
• Langue: English

Extrait

Pipeline integrity audit – Camisea Project

May 2007

The IDB contracted Exponent, Inc., to perform a pipeline integrity analysis of the

project’s downstream component (transportation system), which consists of two buried

pipelines: a natural gas liquids (NGL) and a natural gas. The intent of the analysis was to

develop a risk profile for the two pipelines and identify the factors that contributed to the

five spills in the NGL pipeline that occurred between Dec. 2004 and March 2006.

Exponent is an engineering consulting firm specializing in failure analysis.

The Exponent pipeline integrity analysis evaluated the risk categories that influence the

likelihood and severity of potential pipeline failures. The company identified four

primary categories of risk affecting the integrity of the pipeline: geotechnical, being the

most significant risk factor; and secondary risk factors being river scouring, seismic

events, and mechanical pipe integrity. The higher risk level associated with geotechnical

hazards is a direct consequence of the steep topography, poor soil conditions, and

abundance of water along the pipeline right of way.

Exponent’s analysis identified the factors which contributed to the five spills to be

geotechnical/geological (3 spills), related to a hydrogen induced crack in a weld (1 spill),

and related to scour in a river crossing (1 spill).

Geotechnical and Geology-Related Risks

Exponent’s analysis of load capacity estimates for the Natural Gas Liquid pipeline (NGL)

indicates that while sufficient for internal pressures, it is susceptible to external loading

caused by soil movement. The audit establishes that TgP has adopted several approaches

to reduce this risk. TGP set in motion a geotechnical remediation program in 2006 that

evaluated and mitigated more than 100 sites along the right of way.

Exponent concluded that these measures were generally reliable and robust and being

applied in a consistent and effective manner, substantially reducing the risks associated

with external geotechnical forces. These risks are further reduced by different field

monitoring programs being implemented by TGP. Exponent found that sites in high to

very high geotechnical risks range have been reduced by 90%.

Exponent recommends the construction of additional geotechnical mitigation measures in

2007 to further reduce risks. TgP has incorporated this recommendation into the technical

action plan established with the IDB.

Scour-Related Risks

Based on its review of the scour analyses performed during the design of the project,

Exponent concludes that given the potential uncertainties and the objective to minimize

this risk, additional scour studies and investigation of potential scour mitigation measures

are warranted and currently being evaluated by TGP.

Seismic-Related Risks

Despite the pipe fabricator having commissioned several seismic hazard studies,

Exponent suggests that the potential for permanent ground displacements should be

evaluated more comprehensively and seismic risk management would benefit from an

update of the design ground motions with up to date scientific information.

TgP is engaged in a review of seismic risks to determine whether these are acceptable or

will require an evaluation of potential mitigation measures.

Pipe Integrity

TgP has performed an in-line inspection of the NGL pipeline in 2006 using the magnetic

flux leakage (MFL) inspection tool which has the capacity to detect metal loss and other

potential anomalies. This inspection show that, with the exception of a few locations,

corrosion damage is not an immediate hazard.

The MFL inspection tool was very effective at detecting internal and external corrosion

damage to the pipe, but less effectively at detecting small (less 0.1 mm) preexisting

circumferential cracks. To address this issue, TgP has committed additional resources in

2007 to explore potential options to improve its ability to detect potential small

circumferential cracks.

Construction-related risks

The analysis established that the pipes used for the Camisea transportation system were

purpose-built for this particular project. The pipes were manufactured per the American

Petroleum Institute’s API-5L standard and properly coated to protect them from external

corrosion.

According to Exponent’s report, the construction methods are consistent with general

pipeline construction practice. Risks to the integrity of girth welds and pipes have been

primarily mitigated by the use of x-raying and hydrostatic testing, which led Exponent to

conclude that risks associated with the construction of the pipeline, particularly as it

relates to welds and pipe material, are minimal and consistent with general pipeline

engineering practice.

Design-related risks

Exponent’s analysis established that the Camisea transportation system was designed to

comply with the engineering code requirements of the American Society of Mechanical

Engineers. According to the analysis, the pipe wall thickness is sufficient to contain

internal pressures along the entire length of the pipeline.

Summary

Overall, Exponent concludes that TGP actions have significantly reduced pipeline risk.

TgP has invested roughly $50 million dollars in 2006 for various improvements to reduce

risks to the pipelines, with the majority focused on geotechnical issues and has now

established, in conjunction with IDB, a technical action plan to further improve the

pipeline integrity management. Exponent states that based upon their investigation, TGP

is performing adequate pipeline integrity actions.

In order to continue monitoring the pipeline integrity aspects of the project closely, the

IDB has further retained Exponent to provide continued technical assistance, including

site visits and review of the implementation of the recommended actions.