1 A complete approach to condition monitoring • Engineering • Planning support • Installation • Customer service • Training • Instrument use • Software 2 DOWNTIME CORRECTIVE MAINTENANCE TIME BASED MAINTENANCE PREDICTIVE MAINTENANCE PROACTIVE MAINTENANCE 3 Work Time 1 Many breakdowns - little planning 2 Introduction Predictive Maintenance 3 Few breakdowns - planning 4 Causes of machine failure • 50% Bearing problems • 20% Misalignment • 20% Unbalance • 10% Other reasons 5 5000 h 50 000 h 6 Causes of bearing failure • 40% Lubrication • 30% Vibration • 20% Installation faults • 10% Fatigue failure 7 8 9 10 11 Lubrication Bearing Installation Machine Bearing Alignment Damage Operating Condition 12 GEOMETRIC STATIC AND PRELOAD ALIGNMENT QUALITY OF BEARING DYNAMIC BEARING GEOMETRIC LOAD HOUSE & SHAFT QUALITY LUBRICANT LUBRICANT TOTAL LOAD ROLLING TEMPERATURE SUPPLY VELOCITY LUBRICANT FILM 13 14 Shock Pulse Method 15 Vibration 10 - 1000 Hz 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Input data and Output results 30 Instrument operation 1. Shaft diameter (Bearing inner diameter, Maximum 1999mm) 2. Rotational speed of bearing (RPM, 10 – 19999 RPM) 3. dBi – Decibel initial value is calculated by the instrument after giving shaft diameter and RPM input. (-9 to 40) 31 Output results from the instrument 1. Normalized results - Needs certain input data to evaluate the bearing condition. 2. Un Normalized results- No need of any data input. Instrument displays the absolute shock pulse magnitude in decibel scale 32 Output results • Normalized results - Tester: 1. dBm : Decibel maximum value, Decibel shock value of the shock pulses whose occurrence rate is 5 pulses per second. (-9 to 60 dBN) dBm = dBsv – dBi 2. dBc: Decibel carpet value, Decibel shock value of the shock pulses whose occurrence rate is 300 pulses per second. (-9 to 60 dBN) 33 34 Output results • Un Normalized results - 1. Analyser : Only LR and HR values are displayed when “0” NORM NO. input is given to the instrument. These values can be trended to evaluate the bearing condition. 2. Tester : Only decibel shock values are displayed when “--” dBi input is given to the instrument. These values can be trended to evaluate the bearing condition. 35 Evaluation Of Shock Pulse Readings 36 Three steps in evaluation of readings • Trending • Comparing • Normalising 37 Three steps in evaluation of readings • Trending 1. Collect SPM & VIB readings over a period of time. 2. Plot the graphs and see the variation. • Comparing 1. Compare readings of similar machines. 2. Compare SPM readings with VIB readings and analyze. • Normalizing 1. Establish own limits after hands on experience on the same machine 38 Pressure variation translated into shock pulse pattern The filtered transducer signal reflects the pressure variation in the contact area. When the oil film in the bearing is thick, the shock pulse level is low, without distinctive peaks. The level increases when the oilfilm is reduced, but there are still no distinctive peaks. Damage causes strong pulses at irregular intervals. One can liken the three shock pulse patterns to the vibrations felt in a car while driving on a) a smooth road surface, b) a rough road surface, c) a road full of potholes. 39 Shock pulse pattern of a good bearing Good Bearing : Code : A (Green Zone) Lub No : 1 – 40 1. Low dbc and dbm values 2. dbm – dbc = dB 3. dB value is ideal 4 – 8 dB 4. Trend shows no variation or minor change in dbc/dbm 40 Shock pulse pattern of a Poor lubricated bearing Poor Lubricated Bearing : Code : B (Yellow Zone) Lub No : 0 or 1 Cond : 20 to 30 1. High dbc values, close to dbm 2. dbc – dbm = dB 3. dB value is < 4 dB 4. Trend shows gradual increase in HR reading. 5. Increase in bearing temperature 41 Shock pulse pattern of a damaged bearing Damaged Bearing : Code : C or D (Yellow or Red) Cond No. : 30 to 65 1. High dbm values, Distinctive peaks in shock pulse pattern. 2. dbm–dbc = dB 3. dB value is > 10dB 4. Trend shows gradual increase in LR reading. 5. Increase in bearing temperature 42 43 44 45 46 47 1 48 2 49 3A 50 3B 51 4 52 5 53 6 54 55 56 57 58 59 60 Shock Pulse Method Good bearing Dry running Damaged bearing 61 Bearing life 62