1. INTRODUCTION 2. NEED 3. CONDITION MONITORIN MONITORING G TECHNIQUES 4. EXPERT SYSTEM FOR DIAGNOSIS 5. CASE STUDY 6. CONCLUSION
Condition Monitoring gives information regarding machine health at any given timestamp, in terms of the conditions of signatures. This obviously will help to spot initiation or existance of any misbehavior of the machine so as to diagnose it timely to avoid a big mishap as well as a huge financial and perhaps human loss. Ultimately, Condition Monitoring helps to reduce machine downtime and operating cost enhancing its life.
MONITOR THE FOLLOWING PARAMETERS: Vibration & Noise Temperature Wear Behavior Corrosion Material Defect Acoustic Emission Performance Trend
Ferrography is a technique that is used to seperate
out the ferrous wear debris magnetically. In this method, the larger particles are accumulated at the entry point while the smaller ones at the later part of a tube. A light is passed through this tube which itself passes through magnet. Light is received by a Photo-electric transducer. The light density of the outcoming light decides the strength of particles present in the oil. Normal wear gives more number of smaller particles but a severe one will have greater count of larger particles.
Acoustic emission monitoring basically involves analysis of the sound signals emitted from machines which are in use in the full load condition. It should be noted that the source of AEE is the elastic stress field in the loaded components. Hence, if the structure or a component is not loaded, it can’t emit AEE and method will not be fruitful to be employed. AEM analyses six different AE signal parameters.
Acoustic emission signal parameters: Peak Amplitude Ring Down Count Integrated Event Energy Event Duration Rise Time Spectral Amplitude
Performance Monitoring involves measuring and recording performance parameters & use them for detecting any change in the performance. Parameters ,for say an IC engine, apart from Vibration, may include Power, Fuel Consumption, Pressure, Efficiency, Temperature, Lub-oil consumption rate, Exhaust analysis, etc.
Faults
ηc
P2/P1
T2/T1
Mass flow rate
Vibration
Clogged Filter Surge
Fouling Blade Damage Bearing Failure
Variable
Highly Fluctuating
T Bearing D
Bearing Pressure
Application
Suitable Technique
Gear Drive
Vibration & Noise Monitoring, Wear Analysis
Rolling Bearings
Vibration Monitoring,
Journal Bearings
Temperature Monitoring, Wear Analysis
Reciprocating Engines/Compressors
Vibration, Wear, Performance Trend
Turbines
Vibration, Temperature, Wear. Performance
Pressure Vessels/Process Plant
Thermography, Acoustic Emission, Corrosion
Expert systems attempt to act as a substitute for human experience within the management system. The expert system is developed with sets of rules and logic provided by real human experts. The expert system is available at all times for the many complex questions that arise, whereas human experts are often in great demand. The expert system can also consolidate the knowledge of a number of human experts into a system that is more effective than any one expert working alone. The decisions made by the expert system are consistent and can be explained.
This case study is related to one of the two pumps that supply lube and control oil to a high speed, turbine driven compressor, which is a crucial machine to the running of a continuous process, petro-chemical plant. The pump had been in service for approximately 20 years and the records indicated that it had not required any remedial work on the pump during this time. The machine is on a vibration based condition monitoring schedule and is monitored on a 5 weekly cycle.
This case study is of a two stage in-line reciprocating compressor which is driven by a two speed (960/400 rpm) electric motor via a 9 belt pulley system giving a compressor speed of either 345 rpm or 144 rpm respectively. This machine forms part of a monthly vibration monitoring schedule and is one of a team of three identical units that produce CO2 for the chlorine liquefaction process.
Variety of techniques and systems are available for Condition Monitoring. The main factor to be considered is the question of investment as against the probable loss due to sudden breakdown of machinery which may result in considerable downtime. Condition Monitoring surely proves out to be very effective process that enables us to predict the fault almost 100% perfect, so that necessary actions may be taken to avoid a huge loss both in terms of money, time and sometimes LIFE also.
1.
Nakra B.C., Choudhry K.K., Instrumentation Measurement & Analysis, Tata-McGraw-Hill Publications, 3rd Edition
2.
http://www.avtechnology.co.uk/case_study_files/case_study_12.pdf
3.
Neale Michael John, Tribology Handbook, Butterworth-Heinemann Publications, 2nd Edition (On www.google.co.in)
4. 5.
http://www.avtechnology.co.uk/case_study_files/case_study_45.pdf http://www.electricity-today.com/et/may00/cond.html
