Machinery Dignostic_Introduction pdf info
- 1. BE MECH SEM VII DLOC - 4 MEDLO7041: Machinery Diagnostics By Mr. Sanjay Lohar Asst. Professor, Dept. of Mechanical Engineering, VCET
- 2. Teaching Scheme (Theory) Department Level Optional Course – 4 Course Code Course Name Teaching Scheme (Contact Hours) Credits Assigned Theory Pract Tut. Theory Pract. Tut. Total MEDLO 7041 Machinery Diagnostics 3 -- -- 3 -- -- 3 Course Code Course Name Examination Scheme Theory Term Work Practical Total Internal Assessment End Sem Exam Duration Test 1 Test 2 Average MEDLO 7041 Machinery Diagnostics 20 20 20 80 3 -- -- 100
- 3. Syllabus Theory Module Contents Module 1 1.1 Basics of Vibration Periodic and random motion, Spectral Amplitude Scaling: RMS, Peak and Peak-to-Peak Conversionand Selection, Time and frequency domain analysis, Phase analysis, Orbit analysis, Understanding signal pattern, Importance of speed in accurate diagnosis,Importance of side bands in frequency spectrums. 1.2 Introduction to Vibration based Condition Monitoring MaintenancePrinciples, Vibration based fault Prognosis, Goal of Vibration Monitoring,Steps in Vibration Monitoring,Benefits of Vibration based conditionmonitoring. Module 2 Vibration Measurement Vibration measuring instruments: displacement, velocity, acceleration;Force measurement, Laser based measurements: laser vibrometer Sensor Selection Criteria, Sensor – Mounting Locations and Techniques
- 4. Syllabus Theory Module Contents Module 3 Data Acquisition & Signal Processing Classification of signals,Signal analysis, Fast Fourier Transform (FFT), Essential Settings in Data Acquisition System (Plot Formats, Frequency Span and Frequency Resolution,Average Types and Number of Averages, Windowing, Spectrum Scaling), Signal conditioning Module 4 Machinery Fault Diagnosis I Natural frequency and resonance tests (Practical approach), Time and Frequency domain analysis to identify unbalance, bent shaft, Misalignment, Soft foot conditions, Mechanical looseness
- 5. Syllabus Theory Module Contents Module 5 Machinery Fault Diagnosis II Rolling element bearing and Journal Bearing fault diagnosis, Faults related to Gearbox, vane defects in pumps, Fault in Fans and Blowers. Module 6 Applications of Condition Monitoring Case studies related Balancing Problems in Turbines, ConditionMonitoring in Sugar mills, Health Monitoring of Journal Bearing, ConditionMonitoring of Industrial Pumps. (Aspects to be covered: Selection of sensors, recommended location of sensor, direction of measurement, selection of plot type, Data validationand Identification of Faults)
- 6. M/c health monitoring techniques o Thermography o Wear Debris Analysis o Ultrasonic testing o Radiography o Acoustic Emission o Vibration Analysis ….. Mostly Prefered
- 7. M/c health monitoring techniques • Vibration (Accelerometer) • Wear Debris (Spectrophotometer) • Oil (Particle count meter) • Temperature (IR detectors) • Electrical Current (Hall effect sensor) • Process Parameters (Orifice, Pressure gage)
- 8. Benefits of Vibration Analysis
- 9. Top 5 benefits of vibrationmonitoring •Screen quickly, act quickly. Expanding your maintenance program to include condition monitoring tools gives you deeper, more actionable insights. ... •Organize information for data-driven decisions. ... •Identify potential failures early. ... •Reduce maintenance spend. Vibration monitoring is one of the most effective ways to detect and prevent equipment failure or downtime. 70% of trouble shooting of fault diagnosis or fault identification is done by monitoring vibration produce by machine It can screen most faults including imbalance, misalignment, looseness, and late-stage bearing wear, providing precise warning of impending failure.
- 10. Desirable Vibration • Ultrasonic Cleaning of precision components • Jack Hammer • A guitar string is a good example: When plucked it will vibrate at its natural frequency. • Response of machine to diagnose faults Undesirable Vibration • Fatigue failure • Loosening of hardware or assembly • Human discomfort in operating Jack hammer • Vibration that cause noise
- 11. Failure
- 12. What is Machine Failure
- 13. Types of Machine Failure
- 17. Cause of Machine Failure • Operator Error • Wrong amount of Maintenance • Physical wear and tear • Reliability culture Failing
- 18. Operator Error
- 19. Wrong amount of Maintenance
- 20. Physical wear and tear
- 22. All over the world, plant operators adopt three different types of maintenance techniques for machines, known as the reactive maintenance, preventive maintenance, and predictive maintenance. The benefits of planned maintenance • Eliminate unnecessary maintenance • Reduce rework costs • Reduce lost production caused by failures • Reduce repair parts inventory • Increase process efficiency • Improve product quality • Extend the operating life of plant systems • Increase production capacity • Reduce overall maintenance costs • Increase overall profit Strategies to prevent Machine Failure
- 23. Reactive Maintenance Another name for reactive maintenance is breakdown maintenance. Obviously, in this type of maintenance, no maintenance is done on the machine, and only when the machine fails it is replaced by an entirely new machine. So, in a plant, machines that are very critical and expensive obviously cannot be left to fail by performing reactive maintenance. Usually, the less expensive and noncritical machines can be good candidates for reactive maintenance. For example, in a steel plant one obviously cannot afford to have the blast furnace under a reactive maintenance program, but perhaps a water cooler in the workers’ cafeteria may be a candidate for reactive maintenance
- 24. Attributes of a reactive maintenance program High expenses involved High spare parts inventory cost High overtime labor costs High machine downtime Low production availability
- 25. Preventive Maintenance In preventive maintenance, the maintenance on a particular machine is done in a regular periodic manner at a fixed frequency. This type of maintenance is also known as periodic maintenance Preventive maintenance per the schedule mentioned in the service manual of the vehicle supplied by the manufacturer at a fixed time interval or distance covered by the vehicle However, if this was a vehicle fleet owner having thousands of vehicles, and if all the vehicles had to undergo preventive maintenance as per the OEM schedule, there could be instances where the cost of service would be very high and could have been avoided if only the vehicles whose engine oils had gone bad were replaced and serviced.
- 26. In the armed forces, we would always like the weapons to fire whenever required to do so, army vehicles and naval vessels to move immediately on an order from the field commander, and so on. In such scenarios, cost is not a major criterion, but functionality of the system is. Soldiers would prefer that their gun not malfunction in front of an adversary because it has not been maintained. Which Maintenance you will recommend??? In the armed forces, maintenance of weapons to fire , army vehicles and naval vessels
- 27. Predictive Maintenance In predictive maintenance, maintenance is done on a machine depending on its need. The decision to conduct maintenance or not to conduct maintenance depends upon the machine’s past and present condition. However, in order to know a machine’s condition, additional instrumentation is required on the machine to measure its “health” parameters. This instrumentation includes transducers, signal conditioners, data acquisition units, computer- based signal analysis systems, and software-driven diagnostic routines. Preventive maintenance is a need-based maintenance that depends on the condition of the machine. This type of maintenance is also known as condition-based maintenance.
- 28. Predictive Maintenance Once the machine’s condition is known, it becomes convenient, using simple mathematical models, to determine the reasons behind any impending failure of the machine or diagnose its fault condition. Also, through simple mathematical regression models, the fault prognosis can be done and the remaining useful life of the machine with its present condition can be predicted. Worldwide, it has been reported that over an extended time, predictive maintenance is more economical than preventive maintenance, though it is initially expensive because of the additional requirement of an instrumentation system
- 29. Budget Head Predictive Maintenance Preventive Maintenance Capital MaintenanceEquipment Cost Rs. 5,00,000/- Zero Machine Downtime,Repair & Labor cost per shutdown for repair Rs. 50,000/- Rs. 50,000/- Maintenancecost at end of 1st year Rs. 5,00,000/- Rs. 2,00,000/*- Maintenanceat end of 10 years Rs. 20,00,000/- Maintenancecost at end of 20 years Rs. 7,50,000**/- Rs. 40,00,000/- * Assuming four shutdowns a year **Assuming there are 5 shutdowns between 1st and 20th Year.
- 30. The advantages of the predictive maintenance technique over the other two are many. For instance, it is economic in the long run, it provides a scope for fault prognosis, the maintenance schedule can be controlled according to the availability of resources, the spare parts inventory can be reduced, and the faults in a machine can be minimized. In the long run, this type of maintenance leads to high production rates and increased profitability. • Lower maintenance costs • Fewer machine failures • Less repair downtime • Reduced small parts inventory • Longer machine life • Increased production • Improved operator safety Advantages of the predictive maintenance technique
- 31. Attributes by which a predictive maintenance • User-friendly hardware and software • Automated data acquisition • Automated data management and trending • Flexibility • Reliability
- 32. A successful maintenance program in a plant must have the following • Clearly defined objectives and goals • Measurable benefits • Management support • Dedicated, accountable personnel • Efficient data collection and analysis procedure; viable database • Communication capability • Evaluation procedures • Verification of new equipment condition • Verification of repairs • Overall profitability
- 33. Bath Tub Curve
- 34. Bath Tub Curve
- 35. The infant mortality zone with high failure rates occurs in the early stages of the machine. There could be several reasons for such high failure rates; some of them are faulty installation at the site, ignorance and unfamiliarity of the machine operator, improper electrical power supply, nonavailability of a user or training manual, improper specifications, and choice of the machine. Once the above reasons are sorted out, the machine’s failure rate reduces significantly; this state of the machine continues for a considerable time, which is known as the Useful life of the machine. Finally, toward the end of the useful period, the failure rate of the machine again increases, which can be due to excessive wear and tear on the machine and fatigue failure of the machine component. Though by maintenance the failure rates can be controlled and reduced, a time comes when the cost of maintenance or upkeep is so high that it is better to completely replace the machine with a new one.
- 36. The availability of the machine is defined as the ratio of the useful period (also known as uptime) to the total lifespan of the machine. Maintenance engineers strive to increase the availability of a machine by decreasing the machine’s downtime. The total lifespan of a machine is the summation of the uptime and downtime of the machine.
- 37. Failure Modes Effects and Criticality Analysis (FMECA) FMECA is a methodology widely used in the industry to identify and analyze all potential failure modes of the various parts of a system, determine the effects these failures may have on the system, and how to avoid the failures or mitigate the effects of the failures on the system.
- 38. FMECA can be used for the following objectives: • Assist in selection of design alternatives with high reliability • Ensure that all conceivable failure modes and their effects on operational success of the system have been considered • List potential failures and identify the severity of their effects • Develop early criteria for test planning and test equipment requirement • Provide historical documentation for future reference • Provide a basis for maintenance planning • Provide a basis for quantitative reliability and availability analysis
- 39. Implementation of FMECA for Machinery Maintenance In a large plant, it would be economical or logical to have all equipment under reactive maintenance or predictive maintenance. A FMECA analysis early in the planning stage of maintenance lets one determine the critical machines that will require more attention than the rest
- 40. Risk Priority Number for FMECA Risk matrix or a risk priority number (RPN). The RPN is defined as the product of the following three numbers: O: The rank of occurrence of a failure mode S: The rank of severity of the failure mode D: The rank of ease of not detecting the failure The ranks of O, S, and D can be anywhere from 1 to 10. So, the minimum value of the RPN is 1 and the maximum value is 1000. Machines with a high RPN may undergo predictive maintenance and the machines with a low RPN may undergo reactive maintenance. Risk Priority Number = O × S ×D
- 41. The advantages of permanent, or online, monitoring are: • It is sometimes more economical to have permanently mounted transducers on widely distribute and difficult-to-access machines, such as wind turbines, and automated manufacturing machines, and then the additional cost of transmitting the collected signals back to a centralized monitoring system is economically justified • It reacts very quickly to sudden change and gives the best potential for protecting critical and expensive equipment. • It is the best form of protection for sudden faults that cannot be predicted. An example is the sudden unbalance that can occur on fans handling dirty gas, where there is generally a build-up of deposits on the blades over time. This is normally uniformly distributed but can result in sudden massive unbalance when sections of the deposits are dislodged
- 42. • Since the reaction has to be very quick, permanent monitoring is normally based on relatively simple parameters, such as overall RMS or peak vibration level, and the phase of low harmonics of shaft speed. In general, such simple parameters do not give much advance warning of impending failure. The disadvantages of permanent monitoring are: • The cost of having permanently mounted transducers is very high, so previously could only be justified for the most critical machines in a plant, or where it is difficult for operators to access the machines • Where the transducers are proximity probes, they virtually have to be built into the machine at the design stage, as modification of existing machines would often be prohibitive
- 43. • Much lower cost of monitoring equipment. • The potential (through detailed analysis) to get much more advance warning of impending failure, and thus, plan maintenance work and production to maximize availability of equipment. • It is thus applied primarily where the cost of lost production from failure of the machine completely outweighs the cost of the machine itself. The advantages of intermittent monitoring are:
- 44. • Sudden rapid breakdown may be missed, and in fact where failure is completely unpredictable this technique should not be used. • The lead time to failure may not be as long as possible if the monitoring intervals are too long for economic reasons. This is in fact an economic question, balancing the benefits of increased lead time against the extra cost of monitoring more frequently. The disadvantages of intermittent monitoring are: