Condition Monitoring and Fault Diagnosis of Primary Air Fan

Abstract

Improper channelisation of kinetic energy induces vibrations in machinery. Vibration of mechanical equipment is generally not preferred. Hence, the source of vibration that will lead to failure need to be identified well in advance and corrected to avoid down time of the machine. Vibration has become a scientific tool for fault diagnosis. This paper emphasises monitoring the condition of a primary fan located at a large utility thermal power plant, consisting of 8 units and each, in turn is generating 210 MW. Tri-axial measurements are taken during the period of investigation. Regular logging of the data has provided a basis for performance trend monitoring. Fault diagnosis has been taken-up using ISO 2373 Standards. At the end of the investigation, remedial measures are suggested to bring down the offensive vibration. 1.INTRODUCTION :- Condition Monitoring is the analysis and interpretation of signals sensed by the transducers installed on operational machinery to assess their health. The analysis of the information provided by the transducers is done by using established techniques and interpretation of the evaluated output is considered further to establish what actions are to be taken. Condition monitoring also known as Predictive Maintenance is the technique of monitoring the operating characteristics of the equipment in such a manner that changes in monitored characteristics can be used to predict the need for maintenance well in advance before a serious deterioration or breakdown occurs. It is a quality assurance program for continuous process which inturn increases the production rate reducing downtime of the equipment. Condition monitoring can also be a test and quality assurance system for continuous processes as well as discrete component manufacture. It maximizes the performance of the company's assets by monitoring their condition and ensuring that they are installed and maintained correctly. The technique aims at detecting condition leading to catastrophic breakdown and loss of service, reducing maintenance overhauls, fine tuning of operating equipment, increasing production and operating efficiency and minimizing the replacement parts inventory. This is because a readily monitorable parameter of deterioration can be found in every plant machinery and probabilistic failure of an element in future is highly reduced or almost eliminated thus maximizing the item's life by minimizing the effect of failure. The dynamic behaviour of shafts rotating in bearings has attracted an enormous amount of research interest in the past three decades and have addressed such problems as critical speeds, rotor stability and its responses, nonlinear behaviour of the lubricating oil film etc., There is a growing awareness within production and maintenance circles of the benefits to be enjoyed from vibration based condition monitoring applied to rotating shafts. To increase reliability and accuracy of the monitoring techniques, the parameter identification methods offer potential benefits. The methods have been successfully used in active and adaptive controls of complex machinery. Due to demands of high-speed operation and the use of light structures in primary fans, dynamic measurements are necessary and vibration testing has therefore found wide spread use. The basis for such a health monitoring is to make some relevant calculations together with practical measurements. Primary fan rotors are of steel and stiff. However stiff they deflect by a small amount. This distortion creates 1