May 6, 2003
New risk assessment tools from ABS
In response, ABS is enhancing the development and implementation of its classification rules through the use of risk-based approaches. These allow a better understanding of the risks associated with the operation of purpose-built offshore structures rather than depending upon generic, prescriptive rules and inspection schedules, says William J. Sember, ABS vice president Offshore Development.
"By analyzing case-specific design features and knowing unique elements of the risks involved, industry can take more appropriate measures to mitigate those risks," says Sember. "Similarly, we can determine the types and schedules of inspections that are actually needed rather than those that have been required, sometimes without clear justification, by prescriptive rules."
New risk assessment procedures for innovative designs are developed in the ABS Risk Evaluations for the Classification of Marine-Related Facilities, and new technologies or approaches without much precedent are addressed in the ABS Guidance Notes for Novel Concepts.
A third new publication, the ABS Guide for Surveys Using Risk-Based Inspection Techniques, optimizes inspection resources for existing facilities while maintaining or lowering levels of risk.
The new guides are evolving classification tools that support accelerated innovation in the offshore industry, says James C. Card, senior vice president for Technology at ABS.
"We are poised to present a new set of evaluation metrics," says Card. "Together, these new guides give industry a roadmap to streamlining the process. The guides will allow the industry to work with a larger degree of flexibility rather than be limited to the existing prescriptive rules."
Card says the advantages of using risk evaluations for classification purposes include: an increased ability to review innovative designs; an increased confidence that alternative designs can provide levels of safety equivalent to those of traditional designs; and a better understanding of the hazards, mitigation measures and risks of proposed designs.
"Generally, if an alternative proposal can demonstrate an equivalent level of safety to an original rule, the new guide Risk Evaluations for the Classification of Marine-Related Facilities offers a sound and practical methodology on how to prepare and submit risk evaluations to support a request for classification," says Card.
For example, ABS analysis of an oil tanker model indicates that, in a dual engine room configuration, a single component in the cooling water system in each engine room, with appropriate crossovers, is as safe as the rule-required dual components. The resulting design adjustment, says Card, can deliver significant cost savings while still adhering to the highest safety standards.
The new guide Risk Evaluations for the Classification of Marine-Related Facilities provides alternative methods for supporting the security of life, property and the natural environment through the following subject areas: Objectives and definitions Concepts of safety equivalency Risk evaluation process Basic and detailed risk assessment protocols Documentation and submittal to ABS
In addition, the guide surveys and outlines the use of risk acceptance criteria for the offshore oil production industry, the U.S. Coast Guard, the U.S. Department of Energy and the International Maritime Organization (IMO), among others.
New technologies, concepts and designs have always posed a challenge for the framers of prescriptive standards, but the pace of technological development in the offshore sector is accelerating. As the marine and offshore industries frequently develop novel applications or processes that have no previous experience in newly proposed environments, the existing requirements encompassed in classification rules may not be directly applicable. Card advises that with safety analysis as the key component of the "approval in principle" philosophy, the ABS Guidance Notes for Novel Concepts outlines a new path in classification strategy.
"With the introduction of risk evaluation and novel concept guidance to vessels we cover both ends, from comprehensive approaches entailing significant risk to limited changes or alternatives within pragmatic parameters," says Card. For example, the transportation of Compressed Natural Gas (CNG) to distant markets entails a selection of novel containment alternatives within a comprehensive strategy. Long-range transportation of natural gas, particularly for frontier arenas where there is little or no infrastructure, becomes complicated and expensive because Liquid Natural Gas (LNG) requires special handling on both the delivering and receiving ends, and a limited number of ports can accept the fuel.
Natural gas associated with offshore oil fields, therefore, can be uneconomical to develop and often is either re-injected or flared. To render gas field development more viable for frontier arenas, ABS is currently working with operators and designers to develop various CNG vessels from concept to detailed design with a view to granting class approval in principle.
Various modular containment systems are proposed for these vessels. These systems may consist of either horizontal or vertical bottles ranging from 18 to 36 inches in diameter. An alternative concept uses six-inch diameter coils. These novel concepts provide for a wide range of cargo capacities from 200 to 2,000 million standard cubic feet per day of gas within the same basic design concept.
Rapid advancements in gas transportation methods also have led to significant size increases for LNG carriers and groundbreaking Liquefied Petroleum Gas Floating Production Storage and Offloading (LPG FPSO) vessels. While these complex new designs lack in-service historical experience, risk assessment techniques provide an analytical structure to address issues encountered during the conception, evolution, construction and operation stages.
"With this kind of flexibility, we are moving rapidly past established boundaries for classification services," says Card. These concepts, he adds, also apply to inspection and survey programs aimed at maintaining existing class status. -MORE-
The new ABS Guide for Surveys Using Risk-Based Inspection Techniques is applicable to offshore structures‹FPSOs, tension leg platforms, spars, semisubmersibles and MODUs‹as well as offshore production and processing systems and their associated utility and safety systems. Applications of this guide allow technological approaches that can be shown to demonstrate acceptable levels of safety.
The primary objectives of risk-based inspection (RBI) are to determine the potential consequences and the potential frequency of damage or undesirable events measurable by one or more inspection techniques. Inspection schemes have always considered some elements of risk, but with the availability of RBI in the offshore industry, both consequence and frequency are considered in conjunction within a holistic framework. RBI survey and inspection programs focus resources and activities upon systems and components associated with highest risk. By targeting predictable failure that could affect the safety of an installation, RBI encourages the timely identification of potential damage and repair needs, says Card.
"In the past, high maintenance costs could be incurred by inspecting equipment that processes hazardous materials and relatively non-hazardous equipment simultaneously. For example, non-hazardous equipment such as cooling water systems may often leak, but hazardous dry gas pipelines rarely leak," says Card."At a loss to explain this anomaly, a manager often would be left with little choice but to cut the maintenance and inspection budget," he adds."RBI for the offshore industry actually has arisen from just such circumstances."
Sember notes that prescribed annual inspections have become increasingly difficult for remote locations or areas lacking infrastructure. "Bigger, more expensive, purpose-built facilities have unique operating characteristics. If a deepwater production facility can produce 250,000 barrels of oil per day, it is critical that inspection programs fit in with operational schemes," says Sember.
"A formalized methodology for assessing the unique risks of specific locations and facilities also allows a better and higher level of confidence in safety equivalency," he says.
The ABS Guide for Surveys Using Risk-Based Inspection Techniques facilitates the combined efforts of engineers, surveyors and risk analysts to apply risk-based inspection programs in lieu of traditional class maintenance activities while achieving economical balance and preserving safety. The ABS Guidance Notes for Novel Concepts is better-suited to applications with high degrees of novelty. The document provides a checklist to help determine if proposed designs would be categorized as new or novel with regard to ABS classification.
If a client is proposing an alternative to one or a small number of current rule requirements, the methodologies outlined within the Risk Evaluations for the Classification of Marine-Related Facilities may be more appropriate to gain ABS approval.
"In summary, the ABS trio of guides offer industry a more flexible approach to classification by introducing risk-based methodology in its Rules and regulations," says Card.