Repair Downtime Research Articles

Crashworthiness and dimensional stability analysis of zero Poisson's ratio Fish Cells lattice structures

The present article introduces Zero Poisson's Ratio (ZPR) Fish Cells metamaterial and investigates the effects of Poisson's ratio on the crashworthiness of Positive (PPR), Negative (NPR), and Zero Poisson's ratio lattice structures. High-fidelity Finite Element (FE) models of the proposed sandwich structures are built, based on identical domains for unit cells. Impact performances of lattice structures are addressed for low (2 m/s) and high (5 m/s) impact velocities in three orthogonal directions. The parameters investigated for crashworthiness include impactor's penetration depth, von Mises stress distribution, edges deformation and dimensional stability. Numerical results demonstrate that, unlike PPR and NPR models, the Fish Cells ZPR model possesses greater lateral stability and structural integrity with minimal edge deformations in all three directions. This leads to reduced lateral impact transfer to adjacent components and localised damaged zones, increasing the life span of structural components while reducing maintenance and repair downtime. Experimental analyses are conducted on the Fish Cells metamaterial through a drop tower test for demonstrating agreement with simulations and validation of the proposed modelling approach.

Optimized Design of Source Energy for Manufacturing Machine by Digital Numerical Control

The quality of the power supplied to the machining center is a key factor in determining the accuracy of the machine’s operation. The precision of the machining center is to ensure that the spindle accuracy is less than 3 microns. This study proposes a digital numerical control system to control the quality of the power supply and control the accuracy of the spindle axis of the machining center to monitor the measurement results in real time. The computer vision system is set up according to the artificial intelligent (AI) technique to recognize human face objects and control the position of the processor respectively on each line. The online measurement system follows the digital numerical control (DNC) system applied at each processing line, measuring product dimensions, measuring conditions for setting up machining tools, and measuring machine coordinates. The system operates fully automatically, eliminating dependence on operator skill, and facilitating operation in control of machining conditions. Improve machining center operator satisfaction. After implementation of the improvement options, total cost down 1.740 USD per year, the monthly repair cost due to broken drill, spindle alignment decreased from $5000 to $3,300 per month. The scrap rate related to the hole size decreased from 0.47% to 0.23% (cost down $35 per month). Downtime for repair reduced from 20 hours per month to 7.5 hours per month (cost down $10 per month). Broken drill rate was reduced from 0.20% to 0.06% (cost down $100 per month).

Reengineering of the roller hardening machine of the sheet-rolling shop of JSC Ural Steel

In connection with the planned increase in the production of heat-treated rolled products of large thickness and bridge steel at JSC "Ural Steel", it became necessary to increase the productivity of thermal equipment. For this purpose, the roller hardening machine of the sheet rolling shop was re-engineered. Currently, the lifting and lowering of the lifting frame of the hardening machine is carried out by a spindle drive consisting of an electric motor, a bevel gearbox, spindle gears and cardan shafts. In the process of operation, the equipment of the electromechanical drive for lifting and lowering the pressure frame often fails due to the presence of a large number of rubbing elements, and significant labor costs are required to restore the working condition of the unit. To increase the reliability of the hardening machine, it is proposed to carry out its reengineering by replacing the electromechanical drive of lifting and lowering the pressure frame with a hydraulic drive. Replacing the electric drive with a hydraulic drive is advisable because the existing design already has hydraulic equipment, and at the same time a number of advantages are achieved: stepless regulation of the speed of the output link and ensuring small stable speeds; small size and weight; reversing the movement of the output link of the hydraulic transmission; high performance; Protection against overloads, due to the presence of safety valves, etc. The economic efficiency of design solutions is to reduce the cost of one ton of flat products due to a reduction in repair downtime (by 54 hours) and an increase in production (by 0.9%).

Loss assessment of rigid-frame bridges under horizontal and vertical ground motions

Previous investigations have attributed some reinforced concrete (RC) bridge piers suffered significant damages during large earthquakes due to vertical ground motion effects. This has motivated this study to investigate the use of concrete-filled steel tube (CFST) columns as a more resilient and sustainable alternative to resist combined horizontal and vertical ground motions. The classic performance-based earthquake engineering (PBEE) framework is used to examine the seismic performance of a rigid-frame bridge with construction options of circular RC, circular CFST, and square CFST columns. The hysteretic response of each column is calibrated to the results of hybrid testing of columns under combined horizontal and vertical ground motions. The incremental dynamic analysis (IDA) is conducted using a suite of 50 near-fault records. The results are used to compare the observed damage states and quantify the repair sustainability metrics including repair cost (economic), repair downtime (social), and repair carbon emissions (environmental), as well as the loss of resilience. The losses are integrated with the hazard curves to compute the expected annual losses, all defined as a set of decision variables in the PBEE framework. The results confirm the outstanding seismic performance of CFST columns and highlight their benefits in improving the resilience and sustainability of critical and post-disaster bridges that are prone to strong multi-directional ground motions.

Understanding abrasion-corrosion to improve concrete mixer drum performance: A laboratory and field approach

Two of Brazil's most important economic activities are mining and agribusiness, representing 17.3% of its GDP in 2017. It is crucial to note that water is vital for these prominent sectors and is the principal corrosive agent for carbon steel. The problems concerning wear resistance are closely linked to performance and, therefore, economic issues. Thus, increasingly efficient materials are being used, which are wear-resistant; however, in most cases, corrosion resistance and, more importantly, the combined effect of wear and corrosion are neglected, which accelerate equipment failure. This study specifically focussed on one sector that beneficiates mineral: the concrete industry; laboratory and field tests were performed that compared abrasion-corrosion of A36 common carbon steels, advanced high-strength steels (AHSSs), and ASTM 410 ferritic stainless steels. Initially, a piece of laboratory equipment, which approached actual service conditions, was built by adapting a manual concrete mixer. In the field, samples were placed in sand processing equipment and inside a concrete mixer drum in a truck. In the laboratory, rubber wheel and free-ball microabrasion tests were performed. Both the field and laboratory samples were collected and extensively analysed using SEM and hardness tests. Finally, a complete stainless-steel concrete mixer drum was built, adapted to a truck, and field-tested for five years (beginning in 2015). The useful life of the equipment increased up to three times compared to that made with A36 carbon steel, which is standard in this application. The ferritic stainless steel had better wear performance that AHSSs in a watery concrete environment, despite its lower hardness. In 2020, several companies began using ferritic stainless steel for the maintenance of concrete mixing drums. Manufacturers have also used it as an alternative when a longer service life, reduced downtime for repair, and weight reduction are required.

ДОСЛІДЖЕННЯ НАДІЙНОСТІ ПАРКУ АВТОСАМОСКИДІВ В УМОВАХ ОМЕЛЯНІВСЬКОГО КАР’ЄРУ

Purpose. The aim of the study is to identify the reasons for the decrease in the productivity of dump trucks in the conditions of the Yemelyanovskoye open pit. In the course of the study, data on the movement and maintenance of BelAZ 548 dump trucks in the conditions of the Yemelyanovsky quarry were analyzed. Data processing was carried out by statistical methods. Methods. The publication provides statistical data on the distribution of time for the operations of the cycle of the BelAZ 548 dump truck in the conditions of the Yemelyanovskoye open pit. This type of dump truck is paired with an EKG-5A excavator, which has a bucket volume of 5 m3. In connection with the long-term operation of dump trucks at the Yemelyanovsky quarry, the time spent on the repair of BelAZ is 18…25 % of the calendar time fund. The existing system of maintenance and repair of mining trucks is characterized by the fact that from 8760…8784 hours of the annual calendar fund, the productive time averages 2500…3600 hours, while for 1 hour of productive work of dump trucks, the repair downtime ranges from 0,3…1,1 hours. The production base of the Yemelyanovsky quarry allows for repair work, but in the absence of original spare parts, the dump trucks very quickly return to the repair shops. Also, the performance of dump trucks is affected by the changing conditions of the functioning of vehicles leading to overloads of units and parts of dump trucks. When constructing a mathematical model of the aging dynamics of BelAZ-548 vehicles with a carrying capacity of 40 tons, it was assumed that the output parameters are independent, with the help of which the failure parameter λ(t) changes. Results. Scientific novelty: for the first time for the Yemelyanovsky quarry, the dependence of the performance of the BelAZ 548 dump truck on the transportation distance, which has a linear character, was obtained. And for the first time, the dependence of the failure parameter λ (t) of BelAZ-548 dump trucks on the service life t, which is described by a logarithmic function, was established. Practical significance: it was found that the main breakdowns of BelAZ 548, which make up 90% of all malfunctions, are breakdowns of the engine, drive axle, suspension system, wheels and tires, electrical equipment, transmission system and brake system. Key words: dump truck, downtime, breakdowns, failure parameter, work cycle.

From Mirrors to Free-Space Optical Communication—Historical Aspects in Data Transmission

Fast communication is of high importance. Recently, increased data demand and crowded radio frequency spectrum have become crucial issues. Free-Space Optical Communication (FSOC) has diametrically changed the way people exchange information. As an alternative to wire communication systems, it allows efficient voice, video, and data transmission using a medium like air. Due to its large bandwidth, FSOC can be used in various applications and has therefore become an important part of our everyday life. The main advantages of FSOC are a high speed, cost savings, compact structures, low power, energy efficiency, a maximal transfer capacity, and applicability. The rapid development of the high-speed connection technology allows one to reduce the repair downtime and gives the ability to quickly establish a backup network in an emergency. Unfortunately, FSOC is susceptible to disruption due to atmospheric conditions or direct sunlight. Here, we briefly discuss Free-Space Optical Communication from mirrors and optical telegraphs to modern wireless systems and outline the future development directions of optical communication.

Meningkatkan Kinerja Mesin Extrude Hydron Menggunakan Metode Preventive Maintenance

Background Hydron extrude machines in line 4 have a high enough total downtime, until the October 2019 period with a total of 264, 33 hours. Damage that often occurs in extrude machines from each Extrude Hydron engine subsystem, namely vacuum filter, vacuum hose and digital vacuum indicator. Aim to focus on steps to reduce damage. And from maintenance ensures the level of reliability and readiness while minimizing maintenance costs. Method on the extrude hydron machine is to use visual inspection and quantitative presentation. Results and Discussion Damage that occurs in vacuum filter components that often need to be caused by dust contamination, Automatic sensors (Limit Switch Piston, Pneumatic Limit Switch Cylinderr) are contaminated with dust particles. In repairing the damage that occurs is based on field conditions, so that the repair downtime is quite long due to the availability of spare parts and technical personnel. Conclusion in minimizing damage to extrude hydron machines using preventive maintenance

Predictive Maintenance of Oil and Gas Equipment using Recurrent Neural Network

Oil and gas industry projects involving equipment acquisition and installation are usually capital intensive. The recent crude oil price fall has tightened the expenditure and therefore reinforced the importance of effective maintenance management across the oil and gas industry. Rotating mechanical equipment such as induction motor, compressors and pumps, are essential elements in industrial processes. Effective maintenance of these equipment is crucial to avoid several damage and downtime for repair. Predictive maintenance has attracted huge attention in this industry driven by sensors and data acquisition. This paper focuses on developing machine learning algorithm based on recurrent neural network (RNN) using long short-term memory (LSTM) to carry out predictive maintenance of Air booster compressor (ABC) motor. The resulting experiment demonstrates the performance of RNN-LSTM algorithm implemented for fault prognosis model of rotating equipment predictive maintenance. The application of these algorithms could mitigate risk and reduce cost in the oil and gas operation.

Linking seismic resilience into sustainability assessment of limited-ductility RC buildings

While sustainability addresses the economic, social and environmental impacts distributed over the life cycle of a structure; commonly, ordinary events such as construction, normal operation and ageing are considered and the resilience of the structure to extreme events (natural disasters and man-made hazards) is often ignored. This study aims to introduce a framework to systematically integrate seismic-resilience into sustainability assessment of structures/infrastructures. A case study of a multi-story limited-ductility reinforced-concrete (RC) building with soft-story collapse mechanism is presented. This mode of failure is often expected in regions of low to moderate seismicity, where the detailing is poor. A numerical model is constructed based on the results of a number of multi-axis hybrid simulations allowing to realistically capture the three-dimensional response and the damage states of the RC building first-story columns from linear-elastic range to collapse. In addition, the application of carbon-fiber reinforced polymers (CFRP) as a cost-effective and rapid repair strategy in restoring the building columns is studied. The CFRP repair is proposed as an alternative to the demolition of the full building when subjected to large deformations; thereby, significantly enhancing post-disaster reparability and resilience of the structure. The developed numerical models are then used to quantify the sustainability metrics including repair cost, repair downtime and repair environmental impacts. These metrics are quantified by consecutive hazard, structural response, damage state, and recovery loss analyses in accordance to the PEER PBEE methodology. The results are then used to quantify the resilience parameters, including loss of performance and recovery, using the probabilistic resilience-based earthquake engineering (RBEE) approach.

Financial analysis for optimization of hydropower plants regarding hydro-abrasive erosion: A study from Indian Himalayas

The hydro-abrasive erosion poses challenges for smooth and efficient operation of existing as well as new hydropower plants (HPP). The loss in revenue is caused due to reduced generation on account of reduced efficiency, erosion of plant machinery, down time for repair and maintenance as well as additional expenditure on restoring the machinery and efficiency. In this study, simultaneous measurement of suspended sediment properties (particle size, concentration, shape and mineral content), hydro-abrasive erosion and reduction in efficiency was carried out in a HPP located in Indian Himalayas. The measured values were used, with available models, to calculate gradual loss of efficiency of the turbine and other losses due to repairs, replacements and shutdowns caused by hydro-abrasive erosion. In the financial analysis, costs involved in preventive measures such as coating was included to find out an optimum strategy regarding hydro-abrasive erosion. The losses in operating the uncoated turbine were found about 16% whereas the cost of coating was calculated as 11% of the uncoated turbine cost at the study HPP. The gradual efficiency loss, a major loss, increased rapidly with operation time and amounted to 37% of the total loss. A criterion for decision making was also developed.

Statistical fault diagnosis of wind turbine drivetrain applied to a 5MW floating wind turbine

Deployment of large scale wind turbine parks, in particular offshore, requires well organized operation and maintenance strategies to make it as competitive as the classical electric power stations. It is important to ensure systems are safe, profitable, and cost-effective. In this regards, the ability to detect, isolate, estimate, and prognose faults plays an important role. One of the critical wind turbine components is the gearbox. Failures in the gearbox are costly both due to the cost of the gearbox itself and also due to high repair downtime. In order to detect faults as fast as possible to prevent them to develop into failure, statistical change detection is used in this paper. The Cumulative Sum Method (CUSUM) is employed to detect possible defects in the downwind main bearing. A high fidelity gearbox model on a 5-MW spar-type wind turbine is used to generate data for fault-free and faulty conditions of the bearing at the rated wind speed and the associated wave condition. Acceleration measurements are utilized to find residuals used to indirectly detect damages in the bearing. Residuals are found to be nonGaussian, following a t-distribution with multivariable characteristic parameters. The results in this paper show how the diagnostic scheme can detect change with desired false alarm and detection probabilities.

New Tool for the Evaluation of the Scheduling of Preventive Maintenance for Chemical Process Plants

A new methodology designed to assess the economic value of the scheduling rules for preventive maintenance on a chemical process plant is presented. The methodology is based on the use of a Monte Carlo simulation, which takes into account scenarios that include equipment failure, resources limitations, repair downtime, performance of failed but not repaired equipment due to lack of resources, and some other maintenance rules. The well-known Tennessee Eastman Plant problem is used to illustrate results.

Optimization of Man-Machine System in Weaving Mill

In a weaving mill, an application of the queuing model seems to be relevant to optimize the number of looms to be attended by operators. As the service time for knotting yarn obeys the Erlang distribution, the equation of state probability in the queuing theory will be complicated, and numerical calculation will be very troublesome. Therefore, in most cases, the service time for knotting yarns has been assumed that it obeys the exponential distribution. However, an attempt has been made, in this paper, of the queuing calculation by using each distribution, and got the down time ratio of the loom and the ratio of idle time of operators. The difference of the results of each distribution is so small that the exponential distribution can be used.In this paper, to analyze the unoperating looms due to yarn breakage, the waiting time for an operating round, not considered in the usual queuing theory, is introduced in addition to the ratio of down time for repair and waitingline. The operator's one round time which is one of the parameters to determine an optimal number of operating looms depends on the number of operating looms, their walking time and service factor of their work. According to the expansion of service factors, one round time will be increased greatly and the number of operating looms will be limited.