Operational failure assessment of Remotely Operated Vehicle (ROV) in harsh offshore environments

For an effective integrity assessment of marine robotic in offshore environments, the elements’ failure characteristics need to be understood. A structured probabilistic methodology is proposed for the operational failure assessment (OFA) characteristics of ROV. The first step is to assess the likely failure mode of the ROV system and its support systems. This captures the interaction and failure induced events during operation. The identified potential failure modes are further developed into logical connectivity based on the cause-effect relationship. The logical framework is modeled using the fault tree analysis technique to predict the ROV operational failure probability in an uncertain harsh environment. The fault tree analysis captured the logical relationship between the primary, intermediate, and top events probability. The importance measure criteria were adopted to identify the most probable events, links, and their importance on the failure propagation. The model was demonstrated with an ROV for deep arctic water subsea operations. The result identified the control system, communication linkages, human factor, among others, as most critical in the ROV operational failure. The methodology’s application provides core information on the Mean time between failure (MTBF) of the ROV system that could aid integrity management and provides a guide on early remedial action against total failure.

Step Change in Delivering High Fracture Wells by Eliminating Expandable Liner

This paper discusses the journey of finding alternate solution for having to run the Expandable Liners operations in the Fahud field which is already one of the most operationally challenging fields to drill in Petroleum Development Oman (PDO), due to the presence of a gas cap in highly fractured and depleted limestone formations with total losses and the need for dynamic annulus fill to maintain primary well control. In Fahud field, there is a highly reactive shale formation within reservoir limestone formation. Due to high likelihood of total losses, this shale formation caused bore hole instability challenges while drilling. And with more depletion took place, the challenges became more frequently to occurred. In 2001, expandable tubular liner was introduced to address these bore hole instability challenges while drilling highly reactive shale formation under total losses in the 8-1/2″ section. The use of expandable technology was sustained over the years in delivering all wells drilled to traverse this reactive shale column. Previously before 2001, wells used to have fat well design by installations of extra casing to cover the formations and problematic zones. Also, Fahud field was not depleted as it is now, and the problematic shale zone used to drill by normal conventional way without any issue using inhibition frilling fluid. Petroleum Development Oman (PDO) identified expandable liner as a preferred alternative to ‘Fat’ well design. The ‘Fat’ well design would have a large hole size through potential loss zones, resulting in unmanageable volumes of water being required. Expandable liber was fast-tracked - various technical options were considered by PDO with expandable liner technology being identified as the best solution to address the problem of the shale column. However, the deployment of expandable tubular liner technology supported to drill & deliver wells but also has its associated challenges incurring additional time and cost with reasonable installation and low operations success rate due to number of operational steps required prior and after the expandable liner. Adding to that, all the challenges associated with each step. The installation of the expandable liner required eight operational steps with multiple trips to under-ream, install and expand, cement, caliper log and drill through the liner which increased the probability of something going wrong due to mainly the challenging well profile and multiple operations steps. The expandable liners technology was required when the target formation was below the reactive shale interval. The team carried out a study of previous deployments with the intention of identifying well planning and operational contributors to the installation difficulties and operations failures, with a view of eliminating the need for installing the expandable liner and drilling the well to the desired landing point at designed section total depth. Most of the unsuccessful installation rates were observed to be prevalent in wells with high angle applications. The team also observed that the length of the hole interval below the reactive shale column contributed to the number of unsuccessful installation and operational failure rates recorded. The team evaluated the impact of reducing well inclination on the ability to deliver the hole section without installing the expandable liner. Subsequently the team developed an optimization plan which involved keeping all build activities above and below the problematic interval and holding tangent at less than 45° inclination while drilling across the problematic shale. In conclusion, in 2020 the team delivered six wells (90% of wells crossing reactive shale formation delivered) using the above described approach and traversed the historically highly reactive shale formation without installing expandable liners. This resulted in a 20% reduction in total well construction time and 17% reduction in total well delivery cost per well. In addition to the time and cost saving, with the new approach, described in this paper, less water needed to be pumped for dynamic fill. This allowed bringing the wells quicker to production, thus reducing oil deferment.

ON THE QUESTION OF EVALUATING THE RELIABILITY OF MICROPROCESSORS

The paper considers the trends in the development of foreign microprocessors for comput-ers. Special attention is paid to a series of high-performance Loongson processors manufactured in China. The reliability indicators of processors and models for calculating the operational failure rate are given.

Probability of an Intermediate (Reduced Operational) State

This work examines with the form of the well-known sum: p + q = 1 – which is the sum of the probabilities of opposite events, in particular: the sum of the probabilities of the operational and non-operational (failure) states of a single element (a creation characterised by one output and any number of inputs). It was found that without significantly compromising the accuracy of the previous analyses, it was possible to introduce an additional component to the sum: iiipq3, a component that embodies the probability of an intermediate state, or a reduced operational state. With a constant value of the sum of the components in question, their variation as a function of probability q was determined, following which in the function of the same variable the variation of the entropy of an element's i state was examined using Chapman-Kolmogorov equations; here the focus was on investigating the intensity of the transition from the operational state to the non-operational state or an intermediate state, and from an intermediate state to the non-operational state. The meaning of intermediate probability was also referenced to the object: its diagnostic program, the entropy of structure, the full set of discriminable states, and the relevant transition intensities. It became indispensable in this respect to describe the object using the language of graph theory, in which the basic concepts are layers and an availability matrix. It should be noted that the subject object is an entity that comprises a set of individual elements, with a number and structure of connections that are consistent with the purpose of this entity.

Fuzzy Logic-Based Identification of Railway Wheelset Conicity Using Multiple Model Approach

The deterioration of railway wheel tread causes unexpected breakdowns with increasing risk of operational failure leading to higher maintenance costs. The timely detection of wheel faults, such as wheel flats and false flanges, leading to varying conicity levels, helps network operators schedule maintenance before a fault occurs in reality. This study proposes a multiple model-based novel technique for the detection of railway wheelset conicity. The proposed idea is based on an indirect method to identify the actual conicity condition by analyzing the lateral acceleration of the wheelset. It in fact incorporates a combination of multiple Kalman filters, tuned on a particular conicity level, and a fuzzy logic identification system. The difference between the actual conicity and its estimated version from the filters is calculated, which provides the foundation for further processing. After preprocessing the residuals, a fuzzy inference system is used that identifies the actual conicity of the wheelset by assessing the normalized rms values from the residuals of each filter. The proposed idea was validated by simulation studies to endorse its efficacy.

A Case Study in View of Developing Predictive Models for Water Supply System Management

Initiated by a case study to assess the effectiveness of the modernisation actions undertaken in a water supply system, some R&D activities were conducted to construct a global predictive model, based on the available operational failure and recovery data. The available operational data, regarding the water supply system, are the pipes’ diameter, failure modes, materials, functional conditions, seasonality, and the number of failures and time-to-recover intervals. The operational data are provided by the water company responsible of the supply system. A predictive global model is proposed based on the output of the operational data statistical assessment. It should assess the expected effectiveness of decisions taken in support of the modernisation and the extension plan.

Sandfontein: An Operational Re-examination of the Battle, Contextualised within General J.C. Smuts’ First Phase of the German South West African Campaign 1914

The battle of Sandfontein November 26, 1914 marked the fledgeling Union Defence Force’s first defeat. Historians have used this long-forgotten battle as a lens to view the divisive political and military aspects of the Union’s early history. Unfortunately, some of their scholarship has passed through a distorted lens. Official histories were the first to obfuscate military and leadership shortcomings and interfere with the operational context surrounding Sandfontein. Theirs was for political reasons—a mission to protect delicate reputations and mollify a divided population. Historians have erroneously assumed that General J.C. Smuts’ initial plan for the invasion of German South West Africa 1914 was modified to exclude Walvis Bay/Swakopmund’s occupation. Instead, delays in occupying Walvis Bay/Swakopmund placed the UDF’s forces at Lüderitzbucht in a precarious position. Sandfontein, a desperate attempt to distract the Schutztruppe, was an operational failure, rather than the tactical faux pas portrayed by historians.

SELECTION OF AN OPERATIONAL FAILURE RATE MODEL FOR INTEGRATED CIRCUITS BASED ON EXPERT ANALYSIS OF OPERATING EXPERIENCE

Evaluation of reliability indicators is necessary procedure in the design of a technical system. The article consider two failure rate models for integrated circuits and a number of conclusions, derived from model comparison with operating experience.

FAILURE ANALYSIS AND REDESIGNING OF INTERNAL FIXATION SCREWS

Its highly impossible for false proofing the super structures or mechanisms or the metallurgical methods after installation so they are perfectly engineered and dispatched only after a series of quality checks which has a proper methodology. If this is the scenario with the non living structure's components if they were engineered without errors. There must be some more intensity with the living organisms. living organisms are not engineered but the engineering of the ailments or aids which support the life of living organism must be error free and perfect also must be ready to use. In this context it's pity that there is no perfect operational procedure for internal fixation of fractures this thesis Is focused on that area and aimed to derive a reliable design of internal fixation screw which is designed in contrast with conventional screw This project is stimulation out from two case studies of operational failure implant removal.