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Positive displacement compressors are essential in many engineering systems, from domestic to industrial applications. Many studies have been devoted to providing more insights into the workings and proposing solutions for performance improvements of these machines. This study aims to present a systematic review of published research on positive displacement compressors of various geometrical structures. This paper discusses the literature on compressor topics, including leakage, heat transfer, friction and lubrication, valve dynamics, port characteristics, and capacity control strategies. Moreover, the current status of the application of machine learning methods in positive displacement compressors is also discussed. The challenges and opportunities for future work are presented at the end of the paper.

The operating lifespan of pipelines is limited, defined by their specific design codes and specifications, with the economic justification for this being determined primarily by the pipeline owner. During its operational lifespan, a pipeline’s integrity is affected mainly by the quality of the hydrocarbons being transported. The integrity of a pipeline can be maintained with regular inspections and maintenance/cleaning programmes followed from installation to commissioning. As production matures and declines, operators face several decisions concerning the pipeline’s future. There are several potential scenarios, and each should be assessed on a case-by-case basis for any specific pipeline in question. The industry best practices outline the minimum requirements for the safe decommissioning of pipelines. However, there currently need to be international specifications to be followed for the decommissioning of disused offshore pipelines. This paper aims to provide insight into the decommissioning and abandonment of offshore pipelines. Also, this article provides case studies for the decommissioning of subsea pipelines.

The leak of hydrocarbon-carrying pipelines represents a serious incident, and if it is in a gas line, the economic exposure would be significant due to the high cost of lost or deferred hydrocarbon production. In addition, the leakage of hydrocarbon could pose risks to human life, have an impact on the environment, and could cause an image loss for the operating company. Pipelines are designed to operate at full capacity under steady-state flow conditions. Normal operations may involve day-to-day transients such as the operations of pumps, valves, and changes in production/delivery rates. The basic leak detection problem is to distinguish between the normal operational transients and the occurrence of non-typical process conditions that would indicate a leak. To date, the industry has concentrated on a single-phase flow, primarily of oil, gas, and ethylene. The application of a leak-monitoring system to a particular pipeline system depends on environmental issues, regulatory imperatives, loss prevention of the operating company, and safety policy rather than pipe size and configuration. This paper provides a review of the recommended guidance for leak detection of subsea pipelines in the context of pipeline integrity management. The paper also presents a review of the capability and application of various leak detection techniques that can be used to offer a roadmap to potential users of the leak detection systems.

The sustainability of a manufacturing process can be measured by three main factors which impact both ecological and financial constraints. These factors are the energy required to achieve a specific job, the material utilized for the job, and the time taken to complete that job. These factors have to be quantified and analysed so that a proper manufacturing system can be designed to optimize process sustainability. For this purpose, a computer package, which utilizes life cycle inventory models has been presented for CNC (Computer Numerical Control) milling and turning processes. Based on utilization of resources and production stages, the job completion time for the turning and milling processes can be divided into process (i.e., machining), idle and basic times. As parameters are different for evaluating the process times, i.e., depth and width of cut in case of milling, initial and final diameters for turning, two different case studies are presented, one for each process. The effect of material selection on the sustainability factors has been studied for different processes. Our simulations show that highly dense and hard materials take more time in finishing the job due to low cutting speed and feed rates as compared to soft materials. In addition, face milling takes longer and consumes more power as compared to peripheral milling due to more retraction time caused by over travel distance and lower vertical transverse speeds than the horizontal transverse speed used in a peripheral retraction process.

The optimization process of compressors is usually regarded as a ‘black-box’ problem, in which the mathematical form underlying the relationship between design parameters and the design objective is impractical and costly to be obtained. To solve the ‘black-box’ problem, Bayesian optimization has been proven as an accurate and efficient method. However, the application of such a method in the design of compressors is rarely discussed, particularly no work has been reported in terms of the positive displacement type compressor. Therefore, this paper aims to introduce the Bayesian optimization to the design of positive displacement compressors through the optimization process of the novel limaçon compressor. In this paper, a two-stage optimization process is presented, in which the first stage optimizes the geometric parameters as per design requirements and the second stage focuses on revealing an optimum setting of port geometries that improves machine performance. A numerical illustration is offered to prove the validity of the presented approach.

With the growing demand for high-voltage submarine cables for power transmission in the gas and oil industry and the sheer density of subsea fields, subsea cables’ crossing is unavoidable. However, such cables are not without risks and the deterioration of subsea cables’ crossing is a common issue. In such situations, the articulated padding is usually utilized to provide vertical separation between the crossing subsea cables and the crossed assets. The articulated padding is a lightweight item usually comprised of two polyurethane half discs attached via corrosion-resistant alloy banding or bolts and installed around the crossing cables. In this paper, modified articulated padding is introduced in which the minimum thickness of the load-bearing surface of the padding was increased and the padding profile was changed from a circle to a dodecagon, allowing the most common loading to be changed from a point load to a line load. The modified articulated padding was verified using a physical testing program and finite-element numerical modeling. The physical testing program included a radial load test, an axial load test, a combined radial and axial oscillation load test, and an abrasion test. The results of these tests demonstrated that the modified articulated padding has superior resistance to axial and radial loads when compared to previously used articulated padding. It was also verified that the stress levels in both the modified and previously used articulated paddings remain within the component material limits. However, the factor of safety achieved by the modified articulated padding was more than twice that of the previously used articulated padding. Finally, several Remotely Operated Vehicle (ROV) surveys were also conducted to demonstrate the robustness of the modified articulated padding.

A coordinate measuring machine (CMM) is meant to digitise the spatial locations of points and feed the resulting measurements to a CAD system for storing and processing. For reliable utilisation of a CMM, a calibration procedure is often undertaken to eliminate the inaccuracies which result from manufacturing, assembly and installation errors. In this paper, an Immersion digitizer coordinate measuring machine has been calibrated using an accurately manufactured master cuboid fixture. This CMM has been designed as an articulated manipulator to enhance its dexterity and versatility. As such, the calibration problem is tackled with the aid of a kinematic model similar to those employed for the analysis of serial robots. In addition, a stochastic-based optimisation technique is used to identify the parameters of the kinematic model in order for the accurate performance to be achieved. The experimental results demonstrate the effectiveness of this method, whereby the measuring accuracy has been improved considerably.

Purpose - This paper seeks to describe a design approach which can be used to manufacture better-performing reciprocating compressors. This design approach relates the drive kinematic characteristics to the thermodynamic performance of the compressor.Design methodology approach - The presented approach is based on employing a stochastic optimisation algorithm to find the best piston trajectory within one cycle of operation and couple that with a gradient-based technique to find the best dimensions of the mechanism which can realise this trajectory.Findings - The mathematical models presented to implement the proposed design approach have been coded in a computer program which has been employed for simulation purposes. A case study given at the end of the paper asserts the usefulness of the proposed method and proves that a few percentage points increase in a defined set of performance indices has been gained from the optimisation exercise.Research limitations implications - The presented models are only relevant to reciprocating compressors.Practical implications - The promising results obtained in this paper will lead to the creation of better performing and more reliable compressor drives, designed to fulfil a set of desired performance criteria.Originality value - The paper offers originality in two different aspects. The mechanism design process has been undertaken in full consideration to the thermodynamic performance of the compressor; and the coupling of the stochastic and the gradient-based optimisation methods to produce the desired outcome.

Purpose - This paper aims to replace the complicated iterative procedure used to prevent interference in limaçon-to-limaçon machines by a simplified mathematical equation which can be solved by a straightforward substitution of the required clearance value.Design methodology approach - The input data to the iterative procedure and the obtained results have been employed in regression models to construct the sought after equation. Searching for a proper form of this equation involved numerical experiments to study the effects of the various model parameters on the system response.Findings - The numerical experiments conducted proved to be an effective model construction technique, and the regression model proposed has been found extremely accurate in the specified parameter space.Research limitations implications - The proposed equation is applicable within the parameter range chosen for the study. This range is the one often used for industrial applications. Should the parameters selected for a specific design fall outside the specified range, the proposed model structure may have to be varied to maintain a desirable level of accuracy.Practical implications - The interference study is a part of the iterative procedure employed to design the dimensions of the limaçon-to-limaçon machine. This iterative procedure searches for the proper design amongst hundreds of various possible solutions. The results of this paper will ensure a much faster convergence for the design procedure, since the interference study will be eliminated from the iterative section of the analysis.Originality value - The paper offers a valid and accurate model that can be efficiently used for the intended purpose.

A procedure is proposed for the solution of a set of n linear equations in n unknowns. The procedure involves a vector technique designed to rid the system of three unknowns in each elimination step such that eventually a one-, two- or three-equation set may be obtained and simply solved. The remaining unknowns may then be directly obtained by back-substitution. The method presented is intended to make it easier for engineering students to write their own code to solve systems of linear equations. The familiarity of engineering students with vector techniques enables them to fully assimilate and utilise the concepts presented in this paper.