Reliability Criteria for New and Existing Platforms

Abstract

ABSTRACT Characterization and definition of an acceptable reliability for offshore platforms is a pivotal part of development of design and re-assessment criteria for such structures. This paper outlines several complementary engineering approaches to develop background to reach judgments concerning reliability targets for offshore platforms. These approaches are illustrated with development of reliability targets for design of new and re-qualification of existing PDQ (production-drilling-quarters) platforms. INTRODUCTION Uncertainties result in risks. Risks are an unavoidable reality of any activity. Risks associated with an activity can be reduced to zero only by eliminating the activity. Given that one does not want to abandon the activity, a decision must be reached on how much risk one is willing to take or tolerate. Risks can be expressed as the product of the likelihood of a hazardous event (associated with an activity), and the consequences that could be associated with that event. The consequences can involve property losses, injuries and fatalities, resource losses, productivity or utility losses, and general environmental injuries. Every source of risk can be reduced, and safety increased, by reducing the likelihood of a hazardous event, and/or by reducing the potential consequences associated with the hazardous event. Risks can be reduced only by a considerable expenditure of human effort, materials, services, and other resources. The amount of resources that can be expended on increasing safety is unlimited. However, the resource supply is finite. In addition, the resources are subject to many other competing demands In the context of offshore platforms, one shouldbe prepared to address two choices. First. one should be prepared to choose what risks will be tolerated or accepted. Second, one should be prepared to choose how and how much resources one is willing to invest to achieve the risks that will be tolerated. RISK-DECISION EVALUATIONS In a public-regulatory evaluation of risk, the public-regulatory responsibilities pertain primarily to life safety (injuries and fatalities), resource development, productivity, monetary stability, quality of life, and environmental protections, The primary focus should be from the standpoint of benefits and risks of the public. In the industrial framework, the same factors must be taken into account, but with a smaller segment of the public with its primary focus. In this case, the primary focus should be the benefits and risks to the stockholders and employees of the company. Both the society (country) and industry, in thelong run, must be profitable. That is, their production (value of goods and services) must exceed their costs (resources required for production). If this is not the case, then they will sooner or later go out of business (become bankrupt). Financial stability is dependent on profitability; just as the resources required for safety are dependent on profitability. In the past, the risks associated with alternative activities have been evaluated primarily on the basis of experience and judgment. If the activity failed, by experience, to provide a tolerable balance of risks and benefits, then the activity was re-evaluated, and changed, until a tolerable balance was achieved.