Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Structural Reliability Analysis of a Subsea Pipeline Using API579-1 ASME FFS-1 as Normative Reference
Considering a Model of Depth Growth of Pits over the Operational Life
Mateus Mendes. Miguel; Edilson Gabriel. Veruz; Gilberto Francisco Martha. de Souza; Marcelo Ramos. Martins
Escola Politécnica da Universidade de São PauloSão Paulo, São Paulo, Brazil

Later, at the end of the 1960s, it was discovered that most of theBrazilian oil reserves were located at sea, unlike other countries. Thus,
faced with the challenge of the lack of technologies for this type ofexploration, Brazil took the initiative to produce locally a system ofinnovations that would allow the exploration of oil on the high seas, atechnology known as offshore. Later Brazil acquired the international
title in deepwater oil exploration technology (Neto & Dalla Costa,2007).
The oil exploration in deep waters brings among the challenges thedifficulty of inspecting subsea equipment to verify and guarantee its
integrity due to the occurrence of degradation processes that depend ontime.
Among the degradation processes that depend on time, the corrosion
process has a significant influence on the integrity of the equipment.
Papavinasam (2013) reports that in the USA alone, an annualexpenditure in the production sector is estimated at around 1.372 billion
dollars, of which 1.052 billion dollars (76%) are directly related tocorrosion control. Furthermore, in onshore activities, 30% of downhole
pipe failures are caused by corrosion. For this reason, the investment incorrosion control for offshore operations is much higher, as theinspection hurdles are greater.
After a survey on the Scopus platform 12/18/2021, using the keywords“Oil and Gas” and “Pitting Corrosion” as the starting point, it wasnoted that between 2016 and 2021 approximately 114 publications
were carried out in this area, which 32.5% were published in theMaterials Science area and 17.9% in the Engineering area. An averageof 19 publications per year was obtained, a very low number. However,a search with the keywords “Corrosion” and “Oil and Gas”, provided
that more than 2200 publications were made in the same period. Thisshows that the study of corrosion is relevant, but there are still few
researchers studying the phenomenon of pitting corrosion.
Given the relevance of oil and gas exploration in the world, several
researchers have carried out studies on control and maintenancemethods to ensure that production is optimized.
One of these studies is the one carried out by Unueroh et al (2016). In
it, a case study is carried out in which several types of corrosion foundin a 2A pipe system are characterized. In addition, he analyzed theapplication of the cathodic protection method for corrosion control,
concluding that it is an effective and efficient method when compared

ABSTRACTThis paper aims to analyze the behavior and influence of pitting
corrosion depth over the years in a subsea pipeline used for oil and gas
exploration by a structural reliability approach. The references used tomodel the pit depth and its probability distributions were thedistribution proposed by Velázquez et al (2009) together with the pit
depth growth model proposed by Melchers (2018). A normative reviewof the pitting corrosion assessment chapter of API 579-1 ASME Fitness
For Service (FFS) is intended to develop the limit state equation for thepitting failure mechanism. To calculate the failure probability, theAdvanced First Order Second Moment is used in the limit stateequation for an ASME SA106 pipe (grade B). The research allowed us
to understand the functioning of an operating sector governed bycomplex standards, such as API 579-1 ASME FFS, which has strict
criteria for reliability calculations, as well as performing an analysis ofthe growth in the failure probability over the years due to the influenceof pit depth. The model described was observed to have a high level ofrelevance for professionals seeking to better understand structuralreliability methodologies used in the oil and gas sector, as well as theinfluence that pitting corrosion can exert on a structural failure.

KEYWORDS:Corrosion; Pit Depth; API 579-1 ASME FFS;
Structural Reliability; Oil and Gas.

INTRODUCTION
The economic interest in oil emerged around the 19th century, initiallyused for street lighting before Thomas Edison systematized anddeveloped electrical energy and replaced previously used lighting
sources. Subsequently, with the development of gasoline and diesel
engines, commercial interest in oil grew considerably (Debeir, 1993).
According to Freeman and Soete (2013), the United States of America(USA) was the country that led the scientific learning process for oil
exploration, which was primarily carried out on land. In Brazil, the firstexploration attempts took place at the end of the 19th and beginning of
the 20th century, but onshore exploration had a little result and madethe country abandon the activities (Dias & Quaglino, 1993).

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