Presented By: Michael Miller RE Mason

Transcription

1 Presented By: Michael Miller RE Mason

2 Operational Challenges of Today Our target is zero unplanned downtime Maximize Equipment Availability & Reliability Plan ALL Maintenance HOW? We are trying to be competitive today with a plant that is typically more than 40 years old and so are our competitors. Extend Machinery Life & Rebuilds We are running our equipment beyond its design capacity to handle the variety of materials that we must process Increased throughput without RISK of machine failure? Vibration Basics (Miller) 2

3 Answer These Tough Questions... What maintenance does the machine need during the next planned shutdown? Do I have the parts, do I have the people? Can the equipment run beyond the next scheduled outage? What work can I safely schedule out until the next shutdown? Vibration Basics (Miller) 3

4 What is Vibration? Vibration The motion of a body about a reference point At its simplest, vibration is displayed as displacement over time Vibration Basics (Miller) 4

5 Why Use Vibration Analysis? "Of all the parameters that can be measured non-intrusively in industry today, the one containing the most information on machinery health is the vibration signature." Art Crawford Acknowledged expert in the field of vibration analysis Vibration Basics (Miller) 5

6 Overall Versus Spectrum Overall can let you know that there is a problem Hey Fred, something is wrong with your car! Spectrums can tell you what the problem is Hey Fred, your water pump is bad! Vibration Basics (Miller) 6

7 The Units Displacement accentuates the low frequencies Mils Acceleration accentuates the higher frequencies (g s) Velocity is consistent across a larger range of frequencies Most vibration is analyzed in Velocity since the energy level is consistent throughout the frequency range. Vibration Basics (Miller) 7

8 How do we measure vibration? Three types of sensors Displacement, Velocity, Acceleration Signal processor of some type (CSI 2130) Local or portable display for field analysis Remote Software for viewing and storing collected vibration data Vibration Basics (Miller) 8

9 Displacement Probes Typical Applications Sleeve bearings Most turbine and large motor driven machinery Main turbine generators Boiler feed water pumps Applications in which X Y data is required for measurements such as Shaft centerline from DC gap data Orbits from vibration data Not practical for bearing or gear analysis Vibration Basics (Miller) 9

10 Electromagnetic Induction Vibration Basics (Miller) 10

11 Velocity Pickup Velocity Sensor Application Mounted on case of machine or shaft riders Used on sleeve and roller bearings depending on the application When integration to displacement is required Hi temperature Up to 900 F or higher Vibration Basics (Miller) 11

12 Theory of Operation Velocity Pickups Mechanical Moving coil Bobbin N Bobbin Spring Pole Self powered Directional Magnet S Vibration Basics (Miller) 12

13 Accelerometer Accelerometer Applications Case mounted or magnet mounted Primarily Roller element Bearings and Gears When analysis and diagnostics are important Vibration Basics (Miller) 13

14 Accelerometer Insulator Conductive Plate Insulator Amplifier Preload Bolt Inertial Mass Piezoelectric Crystal Vibration Basics (Miller) 14

15 Frequency Amplitude Vibration Basics (Miller) 15 Time Time Amplitude Amplitude

16 Signal Processing The Mystery Amplitude 0 Turning Speed Time Turning Speed Time Waveform Vibration Basics (Miller) 16

17 Signal Processing Amplitude 0 Turning Speed 2x TS Time Add twice turning speed vibration Vibration Basics (Miller) 17

18 Signal Processing Amplitude Turning Speed 2x TS 7x TS Time Add blade pass vibration Vibration Basics (Miller) 18

19 Signal Processing Amplitude Turning Speed 2x TS 7x TS Brg Time Add Bearing Vibration Vibration Basics (Miller) 19

20 Signal Processing Total Vibration Vibration Basics (Miller) 20

21 Signal Processing break down complex waveform in to waveform components The Fast Fourier Transform (FFT) takes the complex waveform and breaks it down into the component sine waves FFT The amplitudes for each sine wave is then plotted at the frequency of the sine wave, creating the Spectrum Vibration Basics (Miller) 21

22 Signal Processing The FFT or Spectrum Spectrum (FFT) Twice Turning Speed 1 Turning Speed Blade Pass 0.4 Bearing Frequency Amplitude Frequency Vibration Basics (Miller) 22

23 So What can Vibration Analysis Detect? Detect and Track progressing stages of Bearing Failure Identify Imbalance and Misalignment Vibration Analysis is used to correct Imbalance Identify/correct Resonance Identify Mechanical Wear in couplings, bearings, support structures, etc. Detect other defects such as: Lube failure / soft foot / broken rotor bars Pump cavitation, and many more Vibration Basics (Miller) 23

24 What is a Vibration Program? Expertise, Technology, and Work Processes that Prevent Unexpected Downtime By assuring machines do not fail catastrophically Extend Machine Life and Optimize Performance By detecting & correcting root cause conditions that cause excessive wear Allow You To Work Efficiently By trending progressing faults and Coordinating repairs to occur at planned outages Do the right work At the right time With the right methods Vibration Basics (Miller) 24

25 A Few Case Histories to Get You Thinking Paper Mill: On line vibration monitoring detected a cracked shaft Press section Trend increased drastically over 36 hour period Would have otherwise failed catastrophically Offshore Oil Platform: On line vibration monitoring saves compressor twice! Bearing problem detected through vibration analysis. Bearing was replaced. New fault detected 6 hours later Thermal expansion created bearing misalignment Vibration Basics (Miller) 25

26 AFew Case Histories to Get You Thinking Cement Mill: On line vibration monitoring solves mystery Air handler with intermittent high vibration Resonance occurs when baffle open at ~61%. Power Plant: On line vibration extends maintenance intervals Preventive turbine maintenance every 5 years Unnecessary maintenance can induce faults! Extend from 6 10 years with on line monitoring Average repair cost around $1 million Vibration Basics (Miller) 26

27 Where Should Vibration Analysis be Used? Plant Equipment Predictive Critical to production Preventive Support equipment Reactive Easy/Inexpensive to replace Vibration Basics (Miller) 27

28 Establishing a Vibration Program Define program focus / resources Determine collection method(s) Create database Collect data Detect developing faults Diagnose nature and extent of fault Document business and maintenance implications Vibration Basics (Miller) 28

29 1) Define Program Focus Identify Critical Machines Effect on production Availability of back up machine Cost to repair Time to repair Determine Resources Fully in house staffed Fully out sourced Combination: Startup, Initial contract service, etc. Vibration Basics (Miller) 29

30 2) Determine Collection Method(s) Route based periodic General plant equipment Walk around survey Manual measurement Monthly reading typical Readily accessible Online monitoring Critical equipment Installed sensors Automatic monitoring Define measurement interval Inaccessible or hazardous areas Vibration Basics (Miller) 30

31 3) Create Database Enter machine configuration information Machine ID (asset code) and Description Machine Design info, Operating Speed, etc. Define measurement points Point ID (identification) and Description Sensor Type (accelerometer) Analysis Parameters (how to analyze signal) Alarm Limits (allowable amount of vibration) Vibration Basics (Miller) 31

32 Data Collection Points Nomenclature MOH MOP MOV MIH MIP MIV PIH PIP PIV POH POP POV MOA POA Standard: 2 vibration directions per bearing + 1 axial per shaft Add 1 PeakVue point per anti-friction bearing MOH = Motor Outboard Horizontal Vibration Basics (Miller) 32

33 Collect Data (Survey) 1) Periodic survey with walk around Portable Analyzer 2) Continuous survey with online monitoring Vibration Basics (Miller) 33

34 5) Detect Developing Faults Visual detection using color and shape Entire machine train on one screen Vibration divided into frequency bands Motor Gearbox Pump Vibration Basics (Miller) 34

35 6) Diagnose Nature of Fault Each machine fault generates a specific vibration pattern (Bearings, Belts, etc.) A single vibration measurement provides information about multiple components The frequency of the vibration is determined by the machine design and operating speed Vibration Basics (Miller) 35

36 6) Diagnose Nature of Fault Knowing the accurate machine speed and phase is important for vibration analysis. A tachometer is required to determine machine speed and phase. Vibration Basics (Miller) 36

37 6) Diagnose Nature of Fault Trend shows rate of advancement for fault in question Individual trend parameter covers suspect frequency range Vibration Basics (Miller) 37

38 Sub- Harmonic 1X 2X Bearing Bearing Gears Bearing Amplitude 5 mm/sec 1x 2x 50x Trend of Trend of Bearings Balance Time (Days) 1 mm/sec Alarm Time (Days) Alert and Fault alarms for each parameter Vibration Basics (Miller) 38

39 6) Diagnose Nature of Fault Imbalance typically appears at the turning speed of the machine Imbalance Vibration Basics (Miller) 39

40 6) Diagnose Nature of Fault Misalignment typically shows up at either 1 or 2 x turning speed Misalignment Vibration Basics (Miller) 40

41 6) Diagnose Nature of Fault Looseness shows up as multiples of turning speed Looseness Vibration Basics (Miller) 41

42 6) Diagnose Nature of Fault Bearing wear shows up at specific peaks related to the geometry of the bearing and the speed of the shaft. Bearing Wear Vibration Basics (Miller) 42

43 Roller Bearing Faults Four different bearing frequencies Ball Spin Frequency (BSF) Fundamental Train Frequency (FTF) Ball Pass Frequency Inner Race (BPFI) Ball Pass Frequency Outer Race (BPFO) Vibration Basics (Miller) 43

44 Specific peaks typically correlate to Specific machine faults Related to machine speed Need Spectrum Analyzer for diagnostics, not just Overall vibration meter Vibration Basics (Miller) 44

45 Advanced bearing wear shows up clearly in spectrum Vibration Basics (Miller) 45

46 Early bearing wear frequently sometimes can t be detected with standard vibration measurements. Vibration Basics (Miller) 46

47 Sidebands increase with gear wear Many distinct peaks Gear Wear Vibration Basics (Miller) 47

48 Examples of Orbits Misalignment, Resonance, Wear Misalignment Ellipse Truncation Misalignment Shaft rub or mechanical looseness Banana Inside ellipse Misalignment and other problems Sub-synchronous whirl Figure Eight Inner loop Vibration Basics (Miller) 48

49 7) Document Business & Maintenance Implications Document: Diagnoses Recommendations Accuracy Reoccurring faults Production gains Cost savings Financial impact Vibration Basics (Miller) 49

50 Summary: Key Points in a Vibration Program Expertise, Technology, and Work Processes that Prevent Unexpected Downtime By assuring machines do not fail catastrophically Extend Machine Life and Optimize Performance By detecting & correcting root cause conditions that cause excessive wear Allow You to Work Efficiently By trending progressing faults and Coordinating repairs to occur at planned outages Vibration Basics (Miller) 50