Page 444 - Pipeline Pigging Technology

Risk assessment and inspection for integrity

RISK ASSESSMENT AND INSPECTION FOR

STRUCTURAL INTEGRITY

MANAGEMENT

GAS-TRANSMISSION companies are under increasing pressure from sev-
eral directions to develop and manage pipeline integrity programmes in a
responsible and cost-effective manner. The issues of pipeline reliability and
safety of an ageing North American pipeline system are receiving increased
public and regulatory attention. Record gas volumes on NOVA and other
pipeline systems result in operations close to the design capacity for much of
the year, increasing the business emphasis on reliability.
NOVA's operating experience over a period of 32 years has led to the
development and implementation of a comprehensive pipeline integrity
programme that provides a cost-effective contribution to the reliable opera-
tion of the gas-transmission system. This paper describes the methods used
to identify specific pipeline segments for integrity assessment, and the role of
in-line inspection with instrumented pigs, and other monitoring methods, to
ensure safety and reliability of operation by maintaining the structural
integrity of the pipeline system.

INTRODUCTION

The Alberta Gas Transmission system of NOVA, illustrated in Fig.l, has
been developed over a period of 32 years. It transports 13% of the gas
produced annually in Canada and the United States, and virtually all of the gas
exported from the Province of Alberta. The system includes 40 compressor
station sites, and approximately 15,600km (9,700miles) of buried pipeline,
mostly operating in Class 1 locations. The pipelines consist of approximately

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