Related Downtime Research Articles

The influence of infragravity waves, wind, and basin resonance on vessel movements and related downtime at the Outer Port of Punta Langosteira, Spain

The coupling of low-frequency oscillatory modes of a harbor with horizontal motions of moored ships can amplify the latter, causing operational and safety problems. The objectives of this study were to analyze infragravity waves and their effect on moored ship motions; to validate the Wavelet Transform Analysis (WTA) method for studying port-ship resonance in the Outer Port of Punta Langosteira, Spain; and to study the climatic forcing of downtimes. The excited resonant modes of the basin (102 and 132 s) were determined using a numerical model and high-frequency water level measurements at different points of the harbor. Yaw and sway motions of three bulk carriers were analyzed in the frequency-time domain using WTA. The results showed that the oscillation periods of the studied vessel motions are directly related to the water depth to vessel draft ratio. In addition, when the wind speeds exceeds 20 km/h, the ship moves away from the fenders, which lead to a lengthening of these periods. Based on our findings, yaw may induce oscillations of the same period in sway. Additionally, operational thresholds were proposed based on outer and inner waves data that will lead to optimize ship stays, avoiding downtimes, and to advance the safety of loading and unloading operations.

End-of-Life Detection of Power Electronic Converters by Exploiting an Application-Level Health Precursor

Extensive studies have been conducted in regards to estimating the useful life of power electronic converters in order to prevent failure related downtime. The state-of-the-art of converter reliability is based on the physics-of-failure approach, which involves some concerns such as the uncertainty introduced by extrapolating the accelerated test results to other usage conditions, which results in failure probability distributions inhibiting a variance of several years. In order to overcome this issue, the state-of-the-art is currently seeing an increase in research output, which are in favour of basing the reliability studies on physics-of-degradation based methods. The existing methods are restricted to only consider a single component and due to the impracticability of monitoring each single component, there is an essential need for methods, which can monitor the health state of the entire converter. This paper proposes a method which uses the converter operating efficiency to monitor parameter shifts of multiple components, which can be used to gain precision when stating the converter lifetime. A supervised classifier is used to detect the end-of-life while simultaneously coping with the fundamental issue of the loading influencing the efficiency. The method proves to have high accuracy even when measuring inaccuracies are taken into account.

Diagnostics of the Thermal Condition of the Cable Gear Used in the Drive of a Wood Chipper

Early detection of the causes of malfunction of toothed gears, cable gears, and various types of drives enables the prevention of breakdowns and related downtime. The work concerns the possibility of using terminography in order to assess the thermal state of the V-belt of the tension transmission used in the drive of a wood chipper. This device is exposed to dynamic loads and one of the main elements transmitting the drive is a cable gear with a V-belt. The paper presents the use of thermography to evaluate the operation of a cable gear with a heat-welded V-belt. As a diagnostic characteristic, the dependence of temperature changes of the belt and pulleys on the variable load of the chipper over time was adopted. The variable load on the device results from the feeding time of the branches and their cross-section. The aim of the work was to investigate the influence of variable transmission load on the durability and life of the V-belt. It has been found that for the cable transmission it is desirable to ensure that the temperature of the belt around the circumference is similar and changes little.

Enabling Artificial Intelligence as Input Variable Control to Prevent Package Thickness Related Defect in Compression Molding

This paper aims to identify the causes of package thickness related defects in compression mold process. Related defects include wrong package thickness, exposed wire and/or die and mold bleed out.
 There are three scenarios why package thickness problem is encountered in compression molding. These include wrong mold recipe selected against the actual lot, wrong lot loaded against the current recipe loaded and product input to mold having irregularities such as presence of stray die or damage on strip side rails and end rails. Applying artificial intelligence (AI) the mold machine to detect all abnormalities identified at input and prevent it from proceeding to molding.
 Applying AI was able to eliminate occurrence of all package thickness related defects and machine related downtimes.

Laboratory tests of operational durability and energy – efficiency of conveyor belts

The paper presents the results of laboratory tests into the resistance of conveyor belts to simulated wear-related defects such as punctures and longitudinal cuts. Puncture and cut resistance of a conveyor belt have a significant influence on how long the belt can be operated without repairs and the related downtime, and as a result they allow increased operational safety of conveyor belts. The paper also presents a test method and the test results of indentation rolling resistance, which allows evaluating energy-efficiency of conveyor belts. The results here presented confirm that the test rigs and test methods developed at the Wroclaw University of Science and Technology are useful in evaluating the energy-efficiency of conveyor belts and their resistance to simulated wear-related damage.

Statistical Analysis of Component Failures: A 16 Year Survey on More Than 550 Wind Turbines

A good prediction of the failure ratio of wind turbine (WT) components is pivotal to define a correct maintenance program and reduce the downtime periods. Even a small failure can lead to long downtime periods and high repairing costs. The installation sites, which generally have limited accessibility, and the necessity of special facilities to reach the components inside the nacelle, also play a key role in the correct management of WTs. In this study, a detailed survey on the failures occurred to the WTs managed by the Italian operator “e2i energie speciali” (more than 550 machines) over 16 years was performed and the results were analyzed in detail. Each failure was classified by considering the damaged component and the related downtime period. The analysis allowed the determination of several useful results such as the trend of failure occurrence with machine age and the identification of components and macrocomponents which are more critical in terms of both number of occurrences and downtime periods. The combination of component failure occurrences and related downtime periods was also computed to estimate which component is most critical for WT operation.

Improving acquisition efficiency by managing and modelling seismic interference

Renaud Laurain, Francisco Ruiz-Lopez and Seija Eidsvig present an SI QC workflow which reduces the seismic interference related downtime.

ROBUST INTERVAL-BASED MINIMAX-REGRET ANALYSIS METHOD FOR FILTER MANAGEMENT OF FLUID POWER SYSTEM

Fluid contamination is one of the main reasons for the wear failure and the related downtime in a hydraulic power system. Filters play an important role in controlling the contamination effectively, increasing the reliability of the system, and maintaining the system economically. Due to the uncertainties of system parameters, the complicated relationship among components, as well as the lack of effective approach, managing filters is becoming one of the biggest challenges for engineers and decision makers. In this study, a robust interval-based minimax-regret analysis (RIMA) method is developed for the filter management in a fluid power system (FPS) under uncertainty. The RIMA method can handle the uncertainties existed in contaminant ingressions of the system and contaminant holding capacity of filters without making assumption on probabilistic distributions for random variables. Through analyzing the system cost of all possible filter management alternatives, an interval element regret matrix can be obtained, which enables decision makers to identify the optimal filter management strategy under uncertainty. The results of a case study indicate that the reasonable solutions generated can help decision makers understand the consequence of short-term and long-term decisions, identify optimal strategies for filter allocation and selection with minimized system-maintenance cost and system-failure risk.

An application of rock engineering systems for estimating TBM downtimes

TBM performance prediction is essential for estimation of project duration and costs in mechanized tunneling projects. An accurate machine prediction is dependent on rock mass and geological exploration conditions including rock strength, discontinuity conditions, hardness, underground water, poisonous gases, instability and mixed face conditions. The relative contribution of these conditions would have a significant effect in TBM downtimes and reduce the machine utilization considerably. Nonetheless, there are few documents in the literature regarding the prediction of TBM utilization factor. Utilization factor is one of the key performance parameters that links the advance rate and penetration rate, mostly affected by the type of operation, management, maintenance, and geological conditions. Rock engineering system (RES) is a valuable analytical tool for characterizing the important parameters for the interaction mechanisms among variables in rock engineering problems and other engineering practices. The main objective of this study is application of RES for calculating geology and rock mass related downtimes index (GRDi) based on predominant rock mass properties and rock mass related downtimes. This approach was applied to a database of three long mechanized tunnels. Developed database contains geological maps, detailed engineering geology information and daily site reports including length of excavated tunnel in each rock mass units, daily boring time and different rock mass related downtimes. Results of this study showed that GRDi is a robust approach for generating a better fit and producing more reliable and accurate estimation of TBM downtimes compared to conventional statistical methods (R2=0.849).

Evaluation of TBM Utilization Using Rock Mass Rating System: A Case Study of Karaj-Tehran Water Conveyance Tunnel (Lots 1 and 2)

Successful application of a TBM in a project requires investigating both the ground conditions and the machine and backup system design features. Prediction of the machine performance is very important as it has a big effect on the duration of the project and the costs. In this respect, both penetration rate and advance rate must be estimated. Utilization factor, which depends on the type of operation, management, maintenance, geological conditions, mucking delays and other downtimes, correlates the advance rate and penetration rate. Adverse rock mass conditions such as mixed face condition, water problem and instability of rock have a great role in TBM downtimes and reduce the machine utilization considerably. Based on detailed engineering geological reports and maps and daily site reports taken from Karaj-Tehran Water Conveyance Tunnel ( Lots 1 and 2), this paper evaluates, main rock mass properties utilized for the estimation of TBM performance and discusses their effect on the machine utilization. . More specifically it uses the developed database also contains daily boring time, different rock mass related downtimes, daily advance and length of bored tunnel in each engineering geological units. It is concluded that the percentage of the rock mass related downtimes can be estimated via RMR within reliable coefficient of determination.

Effects of key structural parameters on solid–liquid separation behavior of hydrocyclone separator applied to hydraulic oil purification

Contamination control in fluid power system is a challenge due to the fact that it has been one of the major reasons of wear, failure, and the related downtime. A novel hydraulic oil purifier proposed in this study is considered to be capable of removing the solid particle contaminant, moisture, and gas simultaneously, which consists of two parts: hydrocyclone separator and rotating packed bed (i.e. Higee). A hydrocyclone separator used to be applied to chemical industry is tried to be designed according to experiential parameters in a typical fluid power system for the first time. And then, the mathematical model of the hydrocyclone separator has been established. The distribution of the hydraulic oil and solid particles in swirling flow field inside the base hydrocyclone separator has been simulated with the help of computational fluid dynamics software Fluent. The effects of the cone angle and cylindrical length on the separation performance of the hydrocyclone separator have been subsequently investigated. Based on the simulation results, the hydrocyclone separator with 25° cone angle and 60 mm cylindrical length has been considered as the most satisfied configuration. Simulation analysis of the optimal configuration flow field reflects a relatively pleasant solid–liquid separation performance considered to be beneficial to controlling the contamination level of fluid power system. The research outcome will lay a foundation for the development of the new hydraulic oil purifier proposed in this study.

Analysis of Unit Supporting Time and Support Installation Time for Open TBMs

Estimation of advance rate and utilization of tunnel boring machines (TBM) are some of the important steps in planning a TBM tunneling project. Estimation of the utilization factor depends on realistic analysis of downtime components. Among the different parameters influencing TBM downtime, tunnel support is the most influential factor, which can take up to 50% of the total excavation time in some cases. Although, there are some rock mass classification systems specifically developed to link ground conditions with the type and amount of support installed in TBM tunneling, the related downtime for support installation has not been studied in detail. Unit supporting time (UST) is the time required for the installation of ground support per unit length of tunnel. Support installation time (SIT) is the time required for installation of a single ground support element. In this paper, approximate ranges of UST and SIT are discussed and analyzed on the basis of recorded ground SIT from a number of TBM tunneling projects. The primary goal of this paper is to link UST with rock mass classifications that have been specifically developed to assess ground support requirements for different tunnel sections using open-type TBM. An accurate estimate of UST and SIT allows for realistic determination of the related downtime and TBM utilization rate.