Reliability analysis of helicopter emergency flotation system

The reliability of the emergency flotation system of helicopters is analysed by using fault tree analysis and the Monte Carlo method. We constructed a fault tree with the failure of system as the top event and obtained the minimal cut set, the ranking of the structural importance of the bottom events and the probability of the occurrence of the top event. Based on the system fault tree, a Monte Carlo simulation model of the emergency flotation system is established by using Matlab/Simulink. The results show that the Monte Carlo method is feasible and effective for the reliability analysis of the emergency flotation systems of helicopters. Furthermore, the comparison between the criticality importance and mode importance of each subsystem suggests that the control component is the weakest part of the emergency flotation systems, thereby providing a basis for system reliability design and fault diagnosis.

Analisis Penurunan Capaian Target Produksi Bijih Nikel Menggunakan Metode Fault Tree Analysis di PT Ifishdeco Provinsi Sulawesi Tenggara

Abstrak Proses produksi berarti menghasilkan suatu produk yang bernilai guna. Dalam suatu perusahaan pertambangan, produksi merupakan hal yang sangat penting, sehingga diperlukan perencanaan yang matang. Perusahaan menargetkan jumlah bahan galian yang akan diproduksi baik dalam jangka panjang, menengah maupun jangka pendek. Operasi produksi PT. Ifishdeco menggunakan bantuan alat gali muat excavator Komatsu PC 300 dimana terjadi penurunan produksi bijih nikel sebesar 19,94%. Target produksi sebesar 149.934 mt, namun capaian produksi hanya sebesar 116.603mt. Oleh karena itu, penelitian ini dilakukan untuk mengetahui faktor utama dan nilai probabilitas penyebab turunnya capaian produksi. Salah satu metode yang dapat digunakan untuk menganalisis faktor utama penyebab penurunan capaian produksi adalah menggunakan Fault Tree Analysis (FTA). Persamaan logika top down dari Fault Tree Analysis disubstitusi ke dalam aljabar Boolean hingga diperoleh minimal cut set. Minimal cut set merupakan persamaan akhir yang merincikan top down. Top event penurunan capai target produksi memiliki empat top down, yaitu faktor pengisian, kesiapan fisik alat, efektivitas kerja, dan waktu edar alat gali muat. Berdasarkan nilai probabilitas basic event tertinggi yang bernilai 1, maka faktor utama penyebab penurunan capaian produksi adalah dari faktor umur pakai alat tua, penjadwalan perawatan tidak teratur, kualitas alat buruk, dan proses selective mining. Abstract Analysis of Decrease in Nickel Ore Production Targets Using the Fault Tree Analysis Method in PT Ifishdeco, Southeast Sulawesi Province. Production process meant produce product with beneficial value. At the mining company, production was very important, so it needed to be well-planned. Company was making target amount of digging material to be produced in long term, middle term, and short term. Production operation at PT Ifishdeco utilized digger loader equipment namely excavator Komatsu PC 300. There was decreasing in nickel ore production of 19,94%. Production target was 149,934 mt, but the company was only able to meet 116,603 mt. Objective of this study was to know main factor and probability value which caused the low production performance. One of methods to be used to analyze the main factor was Fault Tree Analysis (FTA). Top down logical equations of Fault Tree Analysis was substituted into Boolean algebra to get minimal cut set. Minimal cut set was a formula of the top down and used to calculate probability. Top event of the decreasing of the production target had four top downs which were filling factor, mechanical availability, effectivity of use, and cycle time of digger loader. Based on the highest probability of basic event which value was equal to 1, the main factor caused the decreasing of productivity were lifetime of equipment, unscheduled of maintenance, low quality of equipment, and selective mining. Kata Kunci: Excavator, Work Effectivity, Boolean, Cut Set, Probability

Genome-scale metabolic rewiring improves titers rates and yields of the non-native product indigoidine at scale

High titer, rate, yield (TRY), and scalability are challenging metrics to achieve due to trade-offs between carbon use for growth and production. To achieve these metrics, we take the minimal cut set (MCS) approach that predicts metabolic reactions for elimination to couple metabolite production strongly with growth. We compute MCS solution-sets for a non-native product indigoidine, a sustainable pigment, in Pseudomonas putida KT2440, an emerging industrial microbe. From the 63 solution-sets, our omics guided process identifies one experimentally feasible solution requiring 14 simultaneous reaction interventions. We implement a total of 14 genes knockdowns using multiplex-CRISPRi. MCS-based solution shifts production from stationary to exponential phase. We achieve 25.6 g/L, 0.22 g/l/h, and ~50% maximum theoretical yield (0.33 g indigoidine/g glucose). These phenotypes are maintained from batch to fed-batch mode, and across scales (100-ml shake flasks, 250-ml ambr®, and 2-L bioreactors).

Qualitative Analysis of Commercial Services in MEC as Phased-Mission Systems

Currently, mobile edge computing (MEC) is one of the most popular techniques used to respond to real-time services from a wide range of mobile terminals. Compared with single-phase systems, commercial services in MEC can be modeled as phased-mission systems (PMS) and are much more complex, because of the dependencies across the phases. Over the past decade, researchers have proposed a set of new algorithms based on BDD for fault tree analysis of a wide range of PMS with various mission requirements and failure behaviors. The analysis to be performed on a fault tree can be either qualitative or quantitative. For the quantitative fault tree analysis of PMS by means of BDD, much work has been conducted. However, for the qualitative fault tree analysis of PMS by means of BDD, no much related work can be found. In this paper, we have presented some efficient methods to calculate the MCS encoding by a PMS BDD. Firstly, three kinds of redundancy relations-inclusive relation, internal-implication relation, and external-implication relation-within the cut set are identified, which prevent the cut set from being minimal cut set. Then, three BDD operations, IncRed, InImpRed, and ExImpRed, are developed, respectively, for the elimination of these redundancy relations. Using some proper combinations of these operations, MCS can be calculated correctly. As an illustration, some experimental results on a benchmark MEC system are given.

A literature review on network reliability analysis and its engineering applications

The applications of networks can be observed in numerous engineering realms mainly computers and communication, transportation, electric transmission and oil and gas distribution. Estimating the reliability of such networks is a critical task for the well-being of society as well as a nation. The paradigm of network reliability has evolved considerably over the past few decades. The purpose of this article is to present the developments in network reliability domain in a laconic manner. This paper discusses the various metrics used to evaluate network connectivity along with their mathematical backgrounds. The various algorithms namely State Enumeration, Sum of disjoint product, Minimal Cut Set, Factoring theorem, Cellular Automata, Subset Simulation, Percolation theory, Binary Decision Diagrams, and Universal Generating Functions are enumerated in this review study. The application part of algorithms with their advantages, limitations and scope are presented. Finally, the methodologies used for assessment of network reliability are discussed. This article aims at providing a holistic view of the network reliability practices, which may prove to be helpful for researchers across the globe.

The influence of switching actions with redundant components on the main reliability substations

In this paper is presented a substations reliability analysis based upon substation’s component outage or failure modes. The switching actions can be modelled in the reliability evaluation indices we used the three-state model of the substation components (for example circuit breaker). The reliability indices are evaluated using the minimal cut-set method for each components of substation.

An Application of Fault Tree Analysis for Decommissioning of Subsea Flexible Pipeline in Brazil

The decommissioning of underwater structures has expanded in recent years, as the number of facilities at the end of their useful lives is increasing and legislation becomes more severe. Unlike the production units which already have their decommissioning plans consolidated, subsea pipelines represent the greatest technological, environmental and financial challenge of this stage. Currently, there are few studies to evaluate failures in the decommissioning of flexible pipelines. In addition, these studies generally use simplified analyses. Therefore, this study aims to elaborate a failure analysis for a Reverse Reeling option, in order to contribute to the decision-making process and reduction of failures. For this, a Fault Tree Analysis will be developed followed by the subsequent elaboration of its minimum cut sets. The main results present a total of 13 first-order minimal cut set, 5 second-order minimal cut set and 7 third-order minimal cut set.

Preliminary Hazard Analysis dan Fault Tree Analysis untuk Identifikasi Penyebab Kegagalan Sistem Pelumas Mesin Induk Kapal Penangkap Ikan

Kapal penangkap ikan di Indonesia sebagian besar menggunakan mesin diesel sebagai tenaga penggeraknya. Mesin diesel merupakan mesin mekanis dimana singgungan komponen tidak dapat dihindari, sehingga sistem pelumas mutlak diperlukan untuk mengurangi tingkat kerusakan komponen yang bersinggungan. Penurunan kemampuan sisteem pelumas berdampak pada kerusakan mesin. Tujuan penelitian ini untuk mengidentifikasi penyebab kerusakan sistem pelumas mesin diesel kapal penangkap ikan sehingga memudahkan untuk membuat keputusan dalam melakukan tindakan perawatan dan perbaikan sistem pelumas. Metode untuk mengidentifikasi tiap kegagalan yang mungkin terjadi menggunakan Preliminary Hazard Analysis (PHA) dan Fault Tree Analysis (FTA). PHA merupakan perangkat untuk mengidentifikasi potensi bahaya yang mengakibatkan kegagalan sistem, FTA merupakan perangkat untuk mengidentifikasi penyebab kegagalan sistem. FTA bekerja dengan menentukan kegagalan yang disebut sebagai “top event”, selanjutnya top event diidentifikasi hubungan faktor penyebab berbagai peristiwa kegagalan dengan pohon kesalahan yang menggunakan gerbang logika sederhana “and” dan “or”. Terbentuknya FTA dapat menentukan faktor penyebab kegagalan dengan minimal cut set. Berdasarkan hasil analisis, terdapat tiga penyebab utama mesin diesel mengalami kegagalan karena sistem pelumas adalah gagalnya komponen sistem pelumas yaitu Kebocoran internal, (Screen pelumas + alarm tekanan + manometer + petugas), dan (Pompa pelumas + alarm tekanan + manometer + petugas).