C McCollin

Reliability demonstration for safety-critical systems

This paper suggests a new model for reliability demonstration of safety-critical systems, based on the TRW Software Reliability Theory. The paper describes the model, the test equipment required, and test strategies based on the various constraints occurring during software development. The paper also compares a new testing method, single risk sequential testing (SRST), with the common probability ratio sequential testing method (PRST), and concludes that: (i) SRST provides higher chances of success than PRST; (ii) SRST takes less time to complete than PRST; and (iii) SRST satisfies the consumer-risk criterion, whereas PRST provides a much smaller consumer-risk than the requirement.

SERVQUAL and the process improvement challenge

Service quality is difficult to quantify as it is a function of differing customer perceptions over time, the ever changing market conditions, the measurement process and the interpretation of the data that have been gathered. The SERVQUAL questionnaire and gap analysis have been used to analyse service quality within diverse organisations over the last 30 years. The measurement instrument has been analysed, changed and criticized by numerous authors. However, as a stand-alone tool, it has remained much the same. With organisational emphasis on change in systems as well as new and innovative ways of using computer technology, SERVQUAL is more likely to become obsolete as a stand-alone tool as new ways of collecting and disseminating data become available. However, it might survive if integrated into an ever changing IT framework within a generic company structure such as e.g. the Six Sigma framework. In our paper we strive (1) to find out to what extent is SERVQUAL helpful in process improvement; and (2) to determine characteristics of methodology that would call for application of SERVQUAL for process improvement purposes. Copyright

An optimal statistical testing policy for software reliability demonstration of safety-critical systems

When software reliability demonstration of safety-critical systems by statistical testing is treated as a Test, Analyse and Fix (TAAF) process, an optimal testing policy can be found, which maximises the probability of success of the whole process, over a pre-determined period of time. The optimisation problem is formulated, solved by stochastic dynamic programming, and demonstrated by two numerical examples.

Historical Published Maintenance Data: What Can It Tell Us About Reliability Modelling?

The paper discusses physical assumptions versus statistical assumptions illustrated by some reliability data, which if modelled ignoring physical assumptions (which are more important) gives incorrect results. The importance of physical assumptions can be extended to each stage of systems and service to improve the modelling being done (or that should be done). Explanatory physical information regarding systems is available within reliability data. It just has to be searched for. Four typical data sets are analysed in detail in the paper. In these analyses, an attempt has been made to convert operational time to ‘failure’ to calendar time to maintenance event. There are many other data sets that this straightforward methodology can be applied to. Previous research has developed methods for analysing the operational time of individual equipment but a more comprehensive approach is required to model the whole maintenance system taking into account both the planned and unplanned events. Copyright

Maintenance Planning in a Saudi Arabian Hospital

Abstract Any organization needs maintenance activities on a regular basis to ensure safe and effective operations of its essential facilities. This is particularly true for a hospital where the primary concern is to provide a safe healthcare environment for patients. However, due to the high-risk nature of the operations involved, the maintenance department of a hospital has to develop means of ensuring equipment are operational as any unplanned interruption could adversely affect patient life. This means that potential risks contributing to equipment failure have to be identified and reduced or eliminated. Maintenance activities consume resources, it is therefore important to evaluate different maintenance approaches so that a solution that is fit-for-the-purpose can be implemented to meet specific key performance targets. Several research papers have discussed how optimization of maintenance methodologies may help to improve maintenance organization and reduce costs, thus ensuring long-term sustainability. Three important maintenance management concepts have been identified as suitable options to aid healthcare facility management. These options are Total Preventive Maintenance (TPM), Reliability Centred Maintenance (RCM) and Reliability Centred Failure Analysis (RCFA). The aim of this project is to understand past and current maintenance-related issues, to assess how they impact on business operations, and to identify a means to improve maintenance operations in Saudi hospitals through the development of a new framework incorporating aspects of the three concepts mentioned. Review of applications of engineering management theory and practice and their mapping from the industry sector to the healthcare sector have highlighted a number of key issues which require detailed consideration, namely management policies, working environment, social culture, working culture and decision support systems among others. It became apparent that the framework will need to include a different maintenance performance measurement structure appropriate for hospital environment using approaches including high and low level performance indicators, Six Sigma and Theory of Constraints (TOC).

An availability study for a SME

A case study of an availability analysis for a small commercial company is presented. The analysis was carried out to meet a customer requirement for the availability of an electronic ground-based system in a benign environment. Availability calculations were based on failure data provided and an explanation of the methodology and problems encountered and dealt with are discussed. The methodology includes failure classification according to MIL-HDBK-781A and how it may be used to promote and develop internal processes. A commentary on the background to reliability/availability specification is provided and a number of recommendations for monitoring reliability and availability are given.

Participant observation of a minor train crash

A two‐carriage train crash with a container lorry resulted in minor injuries to various people on board. A description of the event history of the incident including the types of injury and the reaction to shock are described. Corrective actions are discussed including guidelines for treatment to victims of shock, railway staff training in the event of an emergency, an event database and an egress ladder installed into carriage doors. Comparison is made to similar events and their corresponding recommendations, which suggests that a directory of incidents should be set up and maintained so that unambiguous corrective actions can be addressed.