Mechanical failure prevention and condition monitoring have been one of the concerns of mechanical engineers in recent years due to the personal safety, cost of failure, reliability and downtime issues of equipment. Rotating machines are one of the most important actuators in the industrial applications as well as in every day applications. Rolling element bearings are very critical components of rotating machines and the presence of defects in the bearing may lead to failure of machines. Hence, early identification of such defects along with the severity of damage under operating condition of the bearing may avoid malfunctioning and breakdown of machines. Defective bearings are source of vibration and these vibration signals can be used to assess the faulty bearings. This chapter presents the brief review of recent trends in research on bearing defects, sources of vibration and vibration measurement techniques in time domain, frequency domain and time-frequency domain. Detailed explanation of defect detection through scalar indicators in time domain.
TopIntroduction
Different types of machinery are present in the industries. The majority of these machines have rotating components. Machines must perform as per their designed specification and installed capacity to obtain high production rates. Thus, machines must be in proper condition to ensure that they run without significant downtime. Machine condition monitoring deals with the maintenance aspect of these machines based on their past and present condition. Maintenance reduces the risk due to machine failure in a cost effective manner. In order to know the condition of machine sensors are installed around the machine and relevant information is collected, analyzed and decisions are made to take corrective actions so that machine can run as per its design objective. In a plant without proper protocol, in place the end result could be an eventual loss of the plant. Generally, prevention of failure can be identified as the process of fault detection, diagnosis, and prognosis:
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Fault detection is the process in which the measured system data and system status information is observed and it is compared with a normal range of observed attributes to determine whether some measurements fall outside the range representing the healthy condition of the system.
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In Diagnosis condition of failing components is determined, and failure causes is identified.
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In Prognosis impending component failures or abnormal system states are predicted before they actually occur, and estimates remaining useful life of machine.
During the operation machine gives out information or signal in the form of noise vibration, temperature, lubrication oil condition, and the like. These signals are acquired from the machine by installing transducer to measure the mechanical parameter of the machine.
TopPrinciples Of Maintenance
A machine that has been designed and manufactured to perform a certain function, is expected to do so when installed in a plant for its designed life span. However, for reasons beyond ones control, such a machine may fail to do so because of reasons like faulty design of the machine, inferior material and workmanship, incorrect installation and wrong operational procedure, among many others. The machine thus has to be maintained to avoid such failures. All over the world, three different types of maintenance techniques for machines have been adopted by the plant operators, known as the reactive maintenance, preventive maintenance, and predictive maintenance. The benefits of the maintenance are as follows:
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It eliminates unnecessary maintenance,
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Reduce lost production caused by failure,
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Reduce repair part inventory,
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Improve product quality,
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Increase production life of plants,
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Increase production capacity,
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Reduce overall maintenance cost.
Reactive Maintenance
Reactive maintenance is also known as breakdown maintenance is an expensive maintenance method. In this type we need to react because machine is failed completely. The reactive maintenance method result in inefficiencies with significant loss due to unplanned downtime, overtime cost and damaged machinery. Attributes of reactive maintenance programe are as follows:
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Expenses involved are high,
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Spare parts inventory costs are high,
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Machine downtime is high.