This training course is designed to give a detailed examination of the detection, location and diagnosis of faults in rotating and reciprocating machinery using vibration analysis. The basics and underlying physics of vibration signals are first examined. The acquisition and processing of signals is then reviewed followed by a discussion of machinery fault diagnosis using vibration analysis. Hereafter the important issue of rectifying faults that have been identified using vibration analysis is covered. The course is concluded by a review of the other techniques of predictive maintenance such as oil and particle analysis, ultrasound and infrared thermography.
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Practical machinery vibration analysis and predictive maintenance. Machinery — Vibration 2. Vibration — Measurement 3. Machinery — Maintenance and repair I. Title Ltd, Pondicherry, India www. The basics and underlying physics of vibration signals are first examined. The acquisition and processing of signals are then reviewed followed by a discussion of machinery fault diagnosis using vibration analysis.
Hereafter the important issue of rectifying faults that have been identified using vibration analysis is covered. The book is concluded by a review of the other techniques of predictive maintenance such as oil and particle analysis, ultrasound and infrared thermography. The latest approaches and equipment used together with current research techniques in vibration analysis are also highlighted in the text.
These categories are briefly described in Figure 1. This approach works well if equipment shutdowns do not affect production and if labor and material costs do not matter. When unexpected production interruptions occur, the maintenance activities require a large inventory of spare parts to react immediately. Without a doubt, it is the most inefficient way to maintain a production facility.
Futile attempts are made to reduce costs by purchasing cheaper spare parts and hiring casual labor that further aggravates the problem. The personnel generally have a low morale in such cases as they tend to be overworked, arriving at work each day to be confronted with a long list of unfinished work and a set of new emergency jobs that occurred overnight. Here the repair or replacement of damaged equipment is carried out before obvious problems occur.
This is a good approach for equipment that does not run continuously, and where the personnel have enough skill, knowledge and time to perform the preventive maintenance work.
The main disadvantage is that scheduled maintenance can result in performing maintenance tasks too early or too late. Equipment would be taken out for overhaul at a certain number of running hours. It is possible that, without any evidence of functional failure, components are replaced when there is still some residual life left in them. It is therefore quite possible that reduced production could occur due to unnecessary maintenance.
In many cases, there is also a possibility of diminished performance due to incorrect repair methods. In some cases, perfectly good machines are disassembled, their good parts removed and discarded, and new parts are improperly installed with troublesome results. Predictive maintenance basics 3 1.
Mechanical and operational conditions are periodically monitored, and when unhealthy trends are detected, the troublesome parts in the machine are identified and scheduled for maintenance.
The machine would then be shut down at a time when it is most convenient, and the damaged components would be replaced. If left unattended, these failures could result in costly secondary failures.
One of the advantages of this approach is that the maintenance events can be scheduled in an orderly fashion. It allows for some lead-time to purchase parts for the necessary repair work and thus reducing the need for a large inventory of spares. Since maintenance work is only performed when needed, there is also a possible increase in production capacity. A possible disadvantage is that maintenance work may actually increase due to an incorrect assessment of the deterioration of machines.
To track the unhealthy trends in vibration, temperature or lubrication requires the facility to acquire specialized equipment to monitor these parameters and provide training to personnel or hire skilled personnel. The alternative is to outsource this task to a knowledgeable contractor to perform the machine-monitoring duties. If an organisation had been running with a breakdown or preventive maintenance philosophy, the production team and maintenance management must both conform to this new philosophy.
It is very important that the management supports the maintenance department by providing the necessary equipment along with adequate training for the personnel. The personnel should be given enough time to collect the necessary data and be permitted to shut down the machinery when problems are identified. Each failure is analyzed and proactive measures are taken to ensure that they are not repeated. RCFA detects and pinpoints the problems that cause defects. It ensures that appropriate installation and repair techniques are adopted and implemented.
It may also highlight the need for redesign or modification of equipment to avoid recurrence of such problems. As in the predictive-based program, it is possible to schedule maintenance repairs on equipment in an orderly fashion, but additional efforts are required to provide improvements to reduce or eliminate potential problems from occurring repeatedly. Again, the orderly scheduling of maintenance allows lead-time to purchase parts for the necessary repairs.
This reduces the need for a large spare parts inventory, because maintenance work is only performed when it is required. Additional efforts are made to thoroughly investigate the cause of the failure and to determine ways to improve the reliability of the machine. All of these aspects lead to a substantial increase in production capacity. It is also possible that the work may require outsourcing to knowledgeable contractors who will have to work closely with the maintenance personnel in the RCFA phase.
Proactive maintenance also requires procurement of specialized equipment and properly trained personnel to perform all these duties. Presently, the predictive and proactive maintenance philosophies are the most popular.
Breakdown maintenance was practiced in the early days of production technology and was reactive in nature. Equipment was allowed to run until a functional failure occurred. Secondary damage was often observed along with a primary failure. This led to time-based maintenance, also called preventive maintenance. In this case, equipment was taken out of production for overhaul after completing a certain number of running hours, even if there was no evidence of a functional failure.
The drawback of this system was that machinery components were being replaced even when there was still some functional lifetime left in them. This approach unfortunately could not assist to reduce maintenance costs.
Due to the high maintenance costs when using preventive maintenance, an approach to rather schedule the maintenance or overhaul of equipment based on the condition of the equipment was needed. This led to the evolution of predictive maintenance and its underlying techniques.
Predictive maintenance requires continuous monitoring of equipment to detect and diagnose defects. Only when a defect is detected, the maintenance work is planned and executed. Today, predictive maintenance has reached a sophisticated level in industry.
Till the early s, justification spreadsheets were used in order to obtain approvals for condition-based maintenance programs. Luckily, this is no longer the case. The advantages of predictive maintenance are accepted in industry today, because the tangible benefits in terms of early warnings about mechanical and structural problems in machinery are clear. The method is now seen as an essential detection and diagnosis tool that has a certain impact in reducing maintenance costs, operational vs repair downtime and inventory hold-up.
In the continuous process industry, such as oil and gas, power generation, steel, paper, cement, petrochemicals, textiles, aluminum and others, the penalties of even a small amount of downtime are immense. It is in these cases that the adoption of the predictive maintenance is required above all. Through the years, predictive maintenance has helped improve productivity, product quality, profitability and overall effectiveness of manufacturing plants. Predictive maintenance in the actual sense is a philosophy — an attitude that uses the actual operating conditions of the plant equipment and systems to optimize the total plant operation.
It is generally observed that manufacturers embarking upon a predictive maintenance program become more aware of the specific equipment problems and subsequently try to identify the root causes of failures. This tendency led to an evolved kind of maintenance called proactive maintenance. This ensures that they eliminate the causes that may give rise to defects in their equipment in the future. This evolution in maintenance philosophy has brought about longer equipment life, higher safety levels, better product quality, lower life cycle costs and reduced emergencies and panic decisions precipitated by major and unforeseen mechanical failures.
This makes the maintenance work faster and smoother. As machines are stopped before breakdowns occur, there is virtually no secondary damage, thus reducing repair time. For instance, vibration in paper machines has a direct effect on the quality of the paper.
In all probability, the proactive and predictive maintenance philosophy is adopted for critical equipment. Vibration-monitoring instruments are provided with continuous, full-time monitoring capabilities for these machines.
Some systems are capable of monitoring channels simultaneously so that rapid assessment of the entire machine train is possible. For example, centrifugal fans in corrosive service. In many cases, the preventive maintenance philosophy, and at times even a less sophisticated predictive maintenance program is adopted for such equipment.
These essential machines do not need to have the same monitoring instrumentation requirements as critical machines. Vibration-monitoring systems installed on essential machines can be of the scanning type, where the system switches from one sensor to the next to display the sensor output levels one by one.
Usually it is acceptable to adopt the breakdown maintenance philosophy on general purpose equipment. However, in modern plants, even general purpose machines are not left to chance. These machines do not qualify them for permanently installed instrumentation or a continuous monitoring system.
They are usually monitored with portable instruments. Industrial or in-plant average life statistics are not used to schedule maintenance activities in this case. Predictive maintenance monitors mechanical condition, equipment efficiency and other parameters and attempts to derive the approximate time of a functional failure.
Predictive maintenance basics 7 A comprehensive predictive maintenance program utilizes a combination of the most cost-effective tools to obtain the actual operating conditions of the equipment and plant systems.
PRACTICAL MACHINERY VIBRATION ANALYSIS AND PREDICTIVE MAINTENANCE
The book will be providing all interested readers with a remarkably detailed examination of the detection and location as well as the proper diagnostics of possible faults occurring in reciprocating and rotating machinery pieces by means of the vibration analysis. At first, the authors examine the fundamentals and underlying physics theory of the vibration signals. The acquisition and further processing of such signals has been reviewed. The authors have also identified the key issues of the rectification of the relevant faults using the vibration analysis.
Practical Machinery Vibration Analysis and Predictive Maintenance
By Cornelius Scheffer and Paresh Girdhar. Upload Sign In Join. Home Books Science. Create a List. Download to App.
Machinery Vibration Analysis and Predictive Maintenance provides a detailed examination of the detection, location and diagnosis of faults in rotating and reciprocating machinery using vibration analysis. The basics and underlying physics of vibration signals are first examined. The acquisition and processing of signals is then reviewed followed by a discussion of machinery fault diagnosis using vibration analysis. Hereafter the important issue of rectifying faults that have been identified using vibration analysis is covered. The book also covers the other techniques of predictive maintenance such as oil and particle analysis, ultrasound and infrared thermography. The latest approaches and equipment used together with the latest techniques in vibration analysis emerging from current research are also highlighted. Cornelius is one of those rare engineers who combines a deep understanding of the theoretical aspects of condition monitoring with a passion for the practical applications of the technology.