Дослідження надійності та періодичності заміни повітряних фільтрів двигунів

Modern livestock development trends in the agricultural production structure include the use of feed mixers and distribution equipment. However, a stream of malfunctions and failures is reported for mixer-feeders due to factors that are specific to agricultural enterprises in Ukraine, which reduce the operational reliability of feed mixers and distributors. The study aims to evaluate the quantitative indicators of the in-service reliability of mixer-feeders and develop methods to improve them. The reliability test plan [NMT] was used, which implies a certain number of research objects (N), objects undergoing repair in case of performance loss (M), and tests terminated when the operating time (T) is reached. Initial information was collected and processed, and empirical data on the time between failures of KUHN PROFILE 12.2 DS and PROFILE 14.2 DS mixer-feeders in Ukraine were analysed. The analysis established that the faulty condition of mixers-feeders in the initial operation period is caused by the second complexity group failures. Failures related to the loss of the grinding and mixing mechanism, which limits the average time between failures of the feed mixture and distribution equipment, were identified among the second complexity malfunction group. A statistical analysis of the mixer-feeder failure occurrence was carried out. The failure probability of the grinding-mixing mechanism of the feed mixer was determined to be within the normal distribution law. The main parameters of the given theoretical distribution law were determined by calculation results. The calculations determined that the average time between failures is 3152.0 motor-hours; the standard deviation is 902.6 motor-hours; and the coefficient of variation is 0.40. An average time between failures of the study objects was proved to be consistent with the normal distribution law following Kolmogorov’s agreement criterion. Calculations determined that the average reliability index value, according to the normal distribution law, is within the confidence intervals: 1964.2 motor-hours – lower confidence limit; 4339.8 motor-hours – upper confidence limit. The obtained results may be used to improve the mixer-feeder operational reliability

Objective: Arterial stiffness is independent and clinically relevant prognostic biomarker, which can be measured by different techniques, including carotid-femoral Pulse wave velocity (cfPWV), Branchial-ankle PWV baPWV. The aim of this study is to investigate if there is an agreement between ankle-branchial and Carotid-femoral pulse wave velocity. Design and method: The carotid- femoral and Branchio-ankle Pulse wave velocity of 30 patients coming for routine clinical checkup of cardiovascular risk evaluation were measured with SphygmoCor CVSM (Atcor Medical, Australia) and WatchBP Office Vascular (Microlife, Widnau, Switzerland). The mean of left and right leg measurements was used for calculating baPWV, whereas the mean of two measurements on the right side (median for 3) was used for cfPWV. The Bland-Altman Analysis was used for finding the agreement between the two types of pulse wave velocities. Results: 30 patients (63% men, age 66.89 ± 12.75 years, BMI 25.73 ± 3.84 kg/m2, MBP 92.866 ± 10.13 mmHg). CfPWV was 9.80 ± 2.56 m/s and baPWV was 14.24± 2.37 m/s. cfPWV and baPWV were linearly correlated with each other (r = 0.598, p = 0.0005). Both were positively correlated with age (cfPWV: r = 0.6083, p = 0.0004; baPWV r = 0.4716, p = 0.0103). The two metrics showed significant bias (bias CI95% 4.836, 95.0% lower confidence limit 0.901, 95.0% upper confidence limit 8.77). Conclusions: In a population of individuals undergoing cardiovascular screening, a significant bias between Cf-PWV and Ba-PWV was found, in accordance with previous studies. cfPWV and baPWV are correlated each other and showed a similar correlation with age. Larger head-to-head studies are needed to explore differences in relationship with risk factors.

Gradual vascular access port or tunneled central venous catheter occlusion during total parenteral nutrition is a common complication of unknown etiology, usually unresponsive to treatment with urokinase, ethanol, or hydrochloric acid. After establishing safety with regard to catheter materials and efficacy in dissolving the occluding substance in vitro, we treated a total of 13 vascular access ports (10 patients) that had occluded gradually during "three-in-one" total parental nutrition by slow perfusion with 10 to 20 mL of 0.1 mmol/mL sodium hydroxide solution. We found a mean increase in flow (results are flow rates under gravity-dependent vascular access port inlet pressure of 1.5 kPa) from 37 microL/s (95% upper confidence limit, 45 microL/s) to 75 microL/s (95% lower confidence limit, 64 microL/s; p < .001). For normal use, a flow of 50 microL/s is sufficient. There were no side effects. Five vascular access ports remained in excellent function during a follow-up period of 9 months. The others had reocclusions, but the partial reocclusions could be treated successfully.

As a result of tool wear in machining processes there is a change in the dimensions of parts produced. To minimize the cost of producing parts out of specifications and to minimize the overall tooling cost, the optimal tool resetting and replacement intervals need to be determined. In this paper, the optimal cost models are proposed for tool replacement and resetting by using renewal functions. The tool life as well as tool reset times are modelled as inverted normal distributions. Numerical solutions are presented for the proposed models. To illustrate the application of the models, a case study of machining a part on a Mazak CNC machine is presented. The dimensional changes of various surfaces of the machined parts are monitored along with the corresponding tool wear as a function of time. The data obtained have demonstrated the validity of the proposed models, their underlying assumptions, and they illustrate the utilization of such an analysis in a flexible manufacturing system, where such CNC machines are the integral part of the system.

An optimization problem to obtain the optimal replacement interval is studied. The system is minimally repaired at failure and is replaced by a new one at age T. The model assumes that the time horizon associated with the number of replacements is random. The total expected cost is calculated, and the optimal replacement interval minimizing the cost is found. A numerical example is used to compare the costs associated with an infinite time line and a random time line, which this model used.

Preventive maintenance scheduling plays a vital role in any maintenance program. Deciding optimal maintenance interval and replacement interval are the two most important tasks in maintenance optimization. Conventionally, this was done using probability theory that relies on the statistical representation of available information. Possibility approach is, in recent years, gaining popularity, as more often available information is insufficient to identify statistically representative probability distributions. Possibility theory, a variant of fuzzy set theory, is one method that does not require detailed statistical data. This paper tackles the problem of determining the optimal maintenance policy/schedule, based on possibilistic approach. Optimization procedure is dynamic in nature and we have used total budget limit and minimum dynamic reliability as constraints. Fuzzy numbers in dynamic reliability calculations have been used. A detailed algorithm for maintenance and replacement interval optimization is given and results are also presented.

A (τ, T) replacement policy is commonly used to prevent system failure. In previous research, it was assumed that the maintenance time can be ignored since it is negligibly short compared with operation time. However, neglecting maintenance time when optimizing maintenance policies for systems for which the maintenance time is not relatively short can lead to sub-optimal or even incorrect solutions to the problem, resulting in higher maintenance costs. An optimal (τ, T) replacement policy is presented for series systems in which the units deteriorate following different stochastic processes independently. The failure of each unit in the time interval [τ, T) occurs in accordance with a nonhomogeneous Poisson process, the failure is immediately removed by a minimal repair and the system continues operating. The failure of any unit in time interval [τ, T) causes the entire system to fail, which is immediately detected, and corrective maintenance is performed on the whole system. If a failure does not occur during time interval [τ, T), the system receives preventive replacement at T A (τ, T) replacement policy was formulated that considers both preventive and corrective maintenance times and that determines an optimal preventive replacement interval that minimizes the expected long-run cost per unit time. A numerical example illustrates that implementing the proposed (τ, T) replacement policy can effectively reduce maintenance costs.

The present invention relates to an audio amplifier using a pulse width modulation, and more particularly, to a pulse width modulation type audio amplifier which an average switching frequency or a cutoff frequency of a low pass filter is variable in accordance with frequency of input signal. The present invention has a method for using average switching frequency of an output pulse by lowering the average switching frequency in accordance with the bandwidth of the input audio signal for relative narrow bandwidth than that of an input audio signal having a usual bandwidth of 20 kHz like as a pulse width modulation type radio signal and a low bandwidth signal for a subwoofer, a method for lowering a cutoff frequency of a low pass filter for restoring an output pulse to a continuous time signal together an average switching frequency of the output pulse, and a method for using respective average switching frequencies different to each other for each channel having respective different bandwidths in a multi-channel amplifier. By using the average switching frequency as lower as possible in accordance with the bandwidth of the input audio signal, the power efficiency is enhanced and the electromagnetic interference affecting peripheral devices can be minimized.

"The paper discusses the influence of mechanical factors on the performance and aging process of rocking machines, specifically focusing on oilfield equipment such as the downhole rod pump jack. The authors emphasize the importance of analyzing the condition and aging process of oilfield equipment to ensure reliability, safety, and efficiency in oil production processes. The mechanical factors discussed in the paper include vibrations, loads, wear, and corrosion. Vibrations can be caused by improper balance, bearing failures, or other factors, and they have a negative impact on equipment performance and can lead to breakdowns. High mechanical loads associated with raising and lowering sucker rods can cause wear and damage to the pump jack. Operating in harsh environments with sand, abrasive particles, or chemicals can also cause wear on surfaces and equipment parts. Corrosion of metal components can occur due to moisture, chemical attack, or improper storage and maintenance, leading to deterioration and breakage of equipment. The consequences of these mechanical factors on the aging of an oil pump jack include accelerated aging, decreased performance, and an increased risk of accidents. Continuous exposure to vibration, stress, wear, and corrosion accelerates the aging process, resulting in deterioration and reduced equipment life. Damage and breakdowns caused by mechanical factors lead to decreased efficiency, negatively impacting oil production processes. Moreover, insufficient maintenance and failure to address mechanical influences increase the risk of accidents, downtime, and damage to other parts of the manufacturing process. To assess the health and aging status of an oil pump jack, various analysis and diagnostic methods are used, including visual inspection, strength testing, monitoring of parameters, and non-destructive testing. Visual inspection helps identify visible damage, wear, and defects. Strength testing evaluates the reliability of pump jack parts and identifies potential issues. Monitoring parameters like vibrations, temperature, and pressure allows for detecting deviations from normal operation and preventing breakdowns. Non-destructive testing methods such as ultrasonic testing, magnetic particle testing, and radiography help identify hidden defects and damage. The authors recommend several strategies to maintain the reliability and efficiency of an oil pump jack. These strategies include implementing a preventive maintenance program with regular inspection, testing, and parts replacement based on manufacturer’s recommendations and equipment condition analysis. Determining optimal service and part replacement intervals based on historical data, monitoring results, and manufacturer’s recommendations is crucial. Additionally, utilizing more durable materials, anti-corrosion coatings, improved designs, and technologies can increase equipment resistance to mechanical stress and improve performance. The paper also describes the device and components of a pump jack, such as the installation base, platform, balancer, electric motor, crank, connecting rod, and control station. It emphasizes the importance of considering various characteristics when selecting and evaluating the effectiveness of a pump jack, including working load, maximum plunger stroke, reducer dimensions, output torque, and swing frequency. The kinematics of the pump jack drive system are discussed, highlighting the need for reconfiguration to adapt to changing operating conditions and optimize oil production performance. Overall, the paper emphasizes the importance of analyzing mechanical factors, managing the aging process, and implementing maintenance strategies to ensure the reliable and efficient operation of oilfield equipment, specifically the pump jack used in oil production processes.

The purpose of this paper is to propose, motivate and discuss a policy for optimal scheduling replacement intervals of technical systems only on the basis of maintenance cost parameter: a system is replaced by a new one as soon as the maintenance cost within a replacement cycle reaches or exceeds a given level. It is shown that with respect to the long‐run total maintenance cost rate, this policy is superior to the well‐known economic lifetime approach. The simple structure of this policy, the fact that maintenance cost data is usually available and that no lifetime data are required, facilitate its practical application.

Most vehicles in operation are equipped with air filters made of cellulose fiber. Dust particles that are not retained by the air filter reach inside the engine, intensifying its wear. The air filter condition affects economic performance, power and reliability of the internal combustion engine. Properly maintenance of the air filters positively affects engine durability and reduces maintenance costs. The air filter condition is assessed by the restriction generated. This paper investigates to what extent the air filters replaced according to the maintenance schedule recommended by the manufacturer (depending on the distance traveled by the vehicle while using the air filter or the operating time of the air filter) were replaced at the appropriate time. Restriction values generated by seven types of new and used air filter are being presented. The results show that replacing filters according to the maintenance manual and repair is made in most cases prematurely or too late. The paper also draws attention on the default mounting of the air filter that could lead to its damage and consequently allowing unfiltered air entering the engine.

PurposeThe purpose of this paper is to develop a risk‐based integrity model for the optimal replacement of offshore process components, based on the likelihood and consequence of failure arising from time‐dependent degradation mechanisms.Design/methodology/approachRisk is a combination of the probability of failure and its likely consequences. Offshore process component degradation mechanisms are modeled using Bayesian prior‐posterior analysis. The failure consequences are developed in terms of the cost incurred as a result of failure, inspection and maintenance. By combining the cumulative posterior probability of failure and the equivalent cost of degradations, the operational life‐risk curve is produced. The optimal replacement strategy is obtained as the global minimum of the operational risk curve.FindingsThe offshore process component degradation mechanisms are random processes. The proposed risk‐based integrity model can be used to model these processes effectively to obtain an optimal replacement strategy. Bayesian analysis can be used to model the uncertainty in the degradation data. The Bayesian posterior estimation using an M‐H algorithm converged to satisfactory results using 10,000 simulations. The computed operational risk curve is observed to be a convex function of the service life. Furthermore, it is observed that the application of this model will reduce the risk of operation close to an ALARP level and consequently will promote the safety of operation.Research limitations/implicationsThe developed model is applicable to offshore process components which suffer time‐dependent stochastic degradation mechanisms. Furthermore, this model is developed based on an assumption that the component degradation processes are independent. In reality, the degradation processes may not be independent.Practical implicationsThe developed methodology and models will assist asset integrity engineers/managers in estimating optimal replacement intervals for offshore process components. This can reduce operating costs and resources required for inspection and maintenance (IM) tasks.Originality/valueThe frequent replacement of offshore process components involves higher cost and risk. Similarly, the late replacement of components may result in failure and costly breakdown maintenance. The developed model estimates an optimal replacement strategy for offshore process components suffering stochastic degradation. Implementation of the developed model improves component integrity, increases safety, reduces potential shutdown and reduces operational cost.

Filters come in many forms from air filters and shock absorbers to digital filters. Using ideas from everyday filters like air filters, we can understand electronic filters. Electronic filters are familiarly used in audio systems as well as in all physiological measurement systems. During the recording of any signal, some undesirable signals termed “noise” are inevitably picked up. If the signal and noise are well separated in their frequency composition, we can use frequency filters that permit the passage of the desired signal while attenuating the other interfering signals. If the desired signal and the unwanted noise are not distinct, then we have to decide how best to reduce the noise while retaining as much as possible of the signal. This is the concept of an optimal filter. In many natural systems and artificial systems, where the output is affected by variations in the system properties or by disturbances added to the output, the desired response may be better achieved if the system is able to correct itself using some information about the actual output and its deviation from the desired output. Such systems are called feedback systems. The formal analysis of feedback system is useful in not only understanding the benefits of such feedback but also potential problems.

Power transformer malfunctions cause significant power outages and, as a result, material damage. This critical issue must be resolved. Power transformers must be protected from various fault conditions and power system failure. Fuzzy logic is used in this study to detect and protect power system transformer faults. In the simulation system that diagnoses transformer faults and monitors its operating conditions, the fuzzy logic (FL) toolbox in MATLAB/ SIMULINK software was used. The input variables, current and rate of change of current with time, have been identified as "Error" and "Error-Dot" in the programme. The study's findings show that when the output response is zero, the current in the transformer is normal. This is obtained by injecting [0] and [0] input values into the system, resulting in a response of "6e(-017)," which is close to zero. If the output response is greater than zero, the transformer current is rising above normal and the protection scheme should be notified. This condition is achieved by giving the system input values of [-1.5] and [5] and expecting a response of "+5". If the response is less than zero, the transformer current is less than normal, and the protection scheme should be notified. The study concluded that electrical faults and mechanical failures in power transformers can be quickly identified using Fuzzy logic. Thus, power transformer damage is avoided by controlling relays more effectively and quickly. This has resulted in significant savings in maintenance and repair costs. It is assumed that the study was a success. Keywords: Fuzzy logic, Transformer, fault, Detection, Current, Protection

<ns3:p>Two-stage (multi-cyclone-pore-partition) air filters are what protects a vehicle's engine from sucking in mineral dust particles that cause an accelerated wear of internal components. Information on the air filtration process taking place in a two-stage system (multicyclone-baffle filter) of a vehicle's internal combustion engine is not provided often in the available literature. The purpose of this study was to experimentally evaluate paper filters operating directly behind and without a multicyclone system. An original methodology was used, consisting in testing a single cyclone and a paper filter with a suitably sized surface area. While testing the assembly (cyclone-paper filter test), parameters corresponding to those under which two-stage air filters actually operate were maintained, including filtration speed in the paper filter, dust concentration in the air and the cyclone’s inlet velocity. Filtration efficiency and accuracy, as well as pressure drop value were among the parameters determined as a function of dust mass delivered to the unit (cyclone-paper filter) or directly to the filter. The study showed that a paper filter operating downstream from a cyclone operates four times longer before reaching the permissible pressure drop value. During the initial (short) filtration period, separation efficiency values obtained were much lower (w0 = 93.3% without and wc0 = 53.6% with the cyclone, respectively) than the required threshold of 99.5%. The air behind the paper filter contained dust grains with a size of 35-40 m, compared to the required parameter of 2-5 m. Further operation of the filter is characterized by a high separation efficiency of 99.9%, a high accuracy dpmax of 2-5 m and a continuously increasing pressure drop, with the said drop being more intense in the filter without the cyclone system.</ns3:p>