Marvin Rausand

System reliability theory : models and statistical methods

Failure Models. Qualitative System Analysis. Systems of Independent Components. Component Importance. Markov Models. Counting Processes. Dependent Failures. Life Data Analysis. Accelerated Life Testing. Bayesian Reliability Analysis. Reliability Data Sources. Appendices. References. Indexes.

Reliability centered maintenance

Abstract Reliability centered maintenance (RCM) is a method for maintenance planning developed within the aircraft industry and later adapted to several other industries and military branches. This paper presents a structured approach to RCM, and discusses the various steps in the approach. The RCM method provides a framework for utilizing operating experience in a more systematic way. The requirements for reliability models and data are therefore highlighted. The gap between maintenance practitioners and scientists working with maintenance optimization models is discussed, together with some future challenges for RCM.

The basic concepts of failure analysis

This paper discusses basic concepts of failure analysis and gives advice on how to interpret, e.g., function, failure, failure mode, failure cause, and failure effect, using a gate valve as an example. A general approach to identification and classification of functions and failure modes is presented and the various steps of failure analysis are discussed. The OREDA (Offshore Reliability Data) database is used to illustrate the interpretation of the basic concepts. Limitations in the use of OREDA are pointed out and proposals for enhancements of this database are given.

Reliability performance of safety instrumented systems: A common approach for both low- and high-demand mode of operation

Safety instrumented systems (SISs) are usually divided into two modes of operation, low-demand and high-demand. Unfortunately, this classification is not easy to justify and the available formulas that are used to quantify the reliability performance in these two modes of operation are unable to capture combined effects of functional testing, spurious activations, and successful responses to demands. This article discusses some important modeling issues for SIS reliability performance quantification, and demonstrates their implementation in a Markov model. The accuracy of the Markov model for a simple case study of a pressure transmitter is verified through comparison with a scenario-based formula, and it is shown that the Markov approach gives a sufficiently accurate result for all demand rates, covering both low- and high-demand modes of operation.

Reliability assessment of reliquefaction systems on LNG carriers

The paper gives an introduction to reliability assessment of reliquefaction systems for boil-off gas (BOG) on LNG carriers with focus on redundancy optimization and maintenance strategies. The reliability modeling is based on a time-dependent Markov approach. Four different system options are studied, with varying degree of redundancy. Failures in the reliquefaction system may require flaring of the BOG, and the associated cost is compared with the cost of introducing redundancy and the cost of onboard maintenance. A model for maintenance optimization is developed and exemplified on a main unit of the reliquefaction system. Reliability and maintenance cost data for reliquefaction systems on LNG ships are very scarce. The input data have been collected from the best available data sources and adjusted by expert judgement. A tailor-made computer program has been developed and may be supplied to interested readers.

A new approach to production regularity assessment in the oil and chemical industries

Abstract This article presents a new approach to production regularity assessment in the oil and chemical industries. The production regularity is measured by the throughput capacity distribution. A brief survey of some existing techniques is presented, and the structure of the new approach is introduced. The proposed approach is based on analytical methods, i.e. no simulation is necessary. The system modeling is split into three levels: components, basic subsystems, and merged subsystems, and two modeling methods are utilized: Markov modeling and a rule-based method. The main features of the approach are as follows: (1) short calculation time; (2) systems of dependent components can be modeled; (3) maintenance strategies can be modeled; and (4) a variety of system configurations can be modeled. A simple case study is used to demonstrate how the proposed approach can be applied.

Spurious activation of safety instrumented systems in the oil and gas industry : Basic concepts and formulas

Spurious activation of safety instrumented systems in the oil and gas industry may lead to production loss, stress on affected components and systems, and hazards during system restoration. This article defines and clarifies concepts related to spurious activation. A clear distinction is made between spurious operation, spurious trip, and spurious shutdown. The causes and effects of spurious activation are discussed and related to the concepts used in IEC 61508, IEC 61511, and OREDA. A new set of formulas for calculating the spurious activation rate is presented, and compared with formulas that are frequently used in the oil and gas industry. The new approach is illustrated in a simple case study.

Common Cause Failure Modeling: Status and Trends

This chapter presents a status of common cause failure (CCF) modeling. The well known betafactor model is still the most commonly used CCF model. The strengths and limitations of this model are therefore outlined together with approaches to establish plant specific beta-factors. Several more advanced CCF models are also described with a special focus on the new multiple beta-factor model. Problems relating to data availability and estimation of the unknown parameters of the various models are discussed, and ideas for further research are suggested.

Risk of collision between service vessels and offshore wind turbines

Offshore wind farms are growing in size and are situated farther and farther away from shore. The demand for service visits to transfer personnel and equipment to the wind turbines is increasing, and safe operation of the vessels is essential. Currently, collisions between service vessels and offshore wind turbines are paid little attention to in the offshore wind energy industry. This paper proposes a risk assessment framework for such collisions and investigates the magnitude of the collision risk and important risk-influencing factors. The paper concludes that collisions between turbines and service vessels even at low speed may cause structural damage to the turbines. There is a need for improved consideration of this kind of collision risk when designing offshore wind turbines and wind farms.

Product performance and specification in new product development

This paper deals with product performance and specification in new product development. There are many different definitions of performance and specification in the literature. These are reviewed and a new classification scheme for product performance is proposed. The link between performance and specification is discussed in detail using a new model for the new product development process. The new model involves two stages, with each containing three main phases, and is useful for making decisions with regards to product performance and specification.