1. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 SIGNATURE ANALYSIS u Which frequencies exist and what are the relationships to the fundamental exciting frequencies. u What are the amplitudes of each peak u How do the peaks relate to each other u If there are significant peaks, what are their source

2. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 COUPLE UNBALANCE u 180 0 out of phase on the same shaft u 1X RPM always present and normally dominates u Amplitude varies with square of increasing speed u Can cause high axial as well as radial amplitudes u Balancing requires Correction in two planes at 180 o

3. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 OVERHUNG ROTOR UNBALANCE u 1X RPM present in radial and axial directions u Axial readings tend to be in-phase but radial readings might be unsteady u Overhung rotors often have both force and couple unbalance each of which may require correction

4. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 Diagnosing Unbalance Diagnosing Unbalance u Vibration frequency equals rotor speed. u Vibration predominantly RADIAL in direction. u Stable vibration phase measurement. u Vibration increases as square of speed. u Vibration phase shifts in direct proportion to measurement direction. 90 0

5. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ECCENTRIC ROTOR u Largest vibration at 1X RPM in the direction of the centerline of the rotors u Comparative phase readings differ by 0 0 or 180 0 u Attempts to balance will cause a decrease in amplitude in one direction but an increase may occur in the other direction

6. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ANGULAR MISALIGNMENT ANGULAR MISALIGNMENT u Characterized by high axial vibration u 180 0 phase change across the coupling u Typically high 1 and 2 times axial vibration u Not unusual for 1, 2 or 3X RPM to dominate u Symptoms could indicate coupling problems

7. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 PARALLEL MISALIGNMENT PARALLEL MISALIGNMENT u High radial vibration 1800 out of phase u Severe conditions give higher harmonics u 2X RPM often larger than 1X RPM u Similar symptoms to angular misalignment u Coupling design can influence spectrum shape and amplitude Radial 1x2x 4x

8. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 BENT SHAFT u Bent shaft problems cause high axial vibration u 1X RPM dominant if bend is near shaft center u 2X RPM dominant if bend is near shaft ends u Phase difference in the axial direction will tend towards 180 0 difference

9. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 MISALIGNED BEARING u Vibration symptoms similar to angular misalignment u Attempts to realign coupling or balance the rotor will not alleviate the problem. u Will cause a twisting motion with approximately 180 0 phase shift side to side or top to bottom

10. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 OTHER SOURCES OF HIGH AXIAL VIBRATION a. Bent Shafts b. Shafts in Resonant Whirl c. Bearings Cocked on the Shaft d. Resonance of Some Component in the Axial Direction e. Worn Thrust Bearings f. Worn Helical or Bevel Gears g. A Sleeve Bearing Motor Hunting for its Magnetic Center h. Couple Component of a Dynamic Unbalance

11. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 MECHANICAL LOOSENESS (A) u Caused by structural looseness of machine feet u Distortion of the base will cause “soft foot” problems u Phase analysis will reveal aprox 180 0 phase shift in the vertical direction between the baseplate components of the machine

12. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 MECHANICAL LOOSENESS (B) u Caused by loose pillowblock bolts u Can cause 0.5, 1, 2 and 3X RPM u Sometimes caused by cracked frame structure or bearing block

13. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 SLEEVE BEARING WEAR / CLEARANCE PROBLEMS u Later stages of sleeve bearing wear will give a large family of harmonics of running speed u A minor unbalance or misalignment will cause high amplitudes when excessive bearing clearances are present

14. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 COMPONENT FREQUENCIES OF A SQUARE WAVE FORM.

15. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 COMPONENT FREQUENCIES OF A SQUARE WAVE FORM.

16. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 MECHANICAL LOOSENESS (C) u Phase is often unstable u Will have many harmonics u Can be caused by a loose bearing liner, excessive bearing clearance or a loose impeller on a shaft

17. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ROTOR RUB u Similar spectrum to mechanical looseness u Usually generates a series of frequencies which may excite natural frequencies u Subharmonic frequencies may be present u Rub may be partial or through a complete revolution. Truncated waveform

18. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 RESONANCERESONANCE u Resonance occurs when the Forcing Frequency coincides with a Natural Frequency u 180 0 phase change occurs when shaft speed passes through resonance u High amplitudes of vibration will be present when a system is in resonance

19. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 BELT PROBLEMS (D) u High amplitudes can be present if the belt natural frequency coincides with driver or driven RPM u Belt natural frequency can be changed by altering the belt tension u High amplitudes can be present if the belt natural frequency coincides with driver or driven RPM u Belt natural frequency can be changed by altering the belt tension BELT RESONANCE RADIAL 1X RPM BELT RESONANCE

20. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 BELT PROBLEMS (A) u Often 2X RPM is dominant u Amplitudes are normally unsteady, sometimes pulsing with either driver or driven RPM u Wear or misalignment in timing belt drives will give high amplitudes at the timing belt frequency u Belt frequencies are below the RPM of either the driver or the driven u Often 2X RPM is dominant u Amplitudes are normally unsteady, sometimes pulsing with either driver or driven RPM u Wear or misalignment in timing belt drives will give high amplitudes at the timing belt frequency u Belt frequencies are below the RPM of either the driver or the driven WORN, LOOSE OR MISMATCHED BELTS BELT FREQUENCY HARMONICS

21. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 BELT PROBLEMS (C) u Eccentric or unbalanced pulleys will give a high 1X RPM of the pulley u The amplitude will be highest in line with the belts u Beware of trying to balance eccentric pulleys u Eccentric or unbalanced pulleys will give a high 1X RPM of the pulley u The amplitude will be highest in line with the belts u Beware of trying to balance eccentric pulleys RADIAL 1X RPM OF ECCENTRIC PULLEY ECCENTRIC PULLEYS

22. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 BELT PROBLEMS (B) u Pulley misalignment will produce high axial vibration at 1X RPM u Often the highest amplitude on the motor will be at the fan RPM u Pulley misalignment will produce high axial vibration at 1X RPM u Often the highest amplitude on the motor will be at the fan RPM 1X DRIVER OR DRIVEN BELT / PULLEY MISALIGNMENT

23. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 HYDRAULIC AND AERODYNAMIC FORCES u If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitude u High BPF may be present if impeller wear ring seizes on shaft u Eccentric rotor can cause amplitude at BPF to be excessive u If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitude u High BPF may be present if impeller wear ring seizes on shaft u Eccentric rotor can cause amplitude at BPF to be excessive BPF = BLADE PASS FREQUENCY

24. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 HYDRAULIC AND AERODYNAMIC FORCES u Flow turbulence often occurs in blowers due to variations in pressure or velocity of air in ducts u Random low frequency vibration will be generated, possibly in the 50 - 2000 CPM range u Flow turbulence often occurs in blowers due to variations in pressure or velocity of air in ducts u Random low frequency vibration will be generated, possibly in the 50 - 2000 CPM range FLOW TURBULENCE

25. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 HYDRAULIC AND AERODYNAMIC FORCES u Cavitation will generate random, high frequency broadband energy superimposed with BPF harmonics u Normally indicates inadequate suction pressure u Erosion of impeller vanes and pump casings may occur if left unchecked u Sounds like gravel passing through pump u Cavitation will generate random, high frequency broadband energy superimposed with BPF harmonics u Normally indicates inadequate suction pressure u Erosion of impeller vanes and pump casings may occur if left unchecked u Sounds like gravel passing through pump CAVITATION

26. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 BEAT VIBRATION u A beat is the result of two closely spaced frequencies going into and out of phase u The wideband spectrum will show one peak pulsating up and down u The difference between the peaks is the beat frequency which itself will be present in the wideband spectrum u A beat is the result of two closely spaced frequencies going into and out of phase u The wideband spectrum will show one peak pulsating up and down u The difference between the peaks is the beat frequency which itself will be present in the wideband spectrum WIDEBAND SPECTRUM ZOOM SPECTRUM F1 F2

27. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ELECTRICAL PROBLEMS u Stator problems generate high amplitudes at 2F L (2X line frequency ) u Stator eccentricity produces uneven stationary air gap, vibration is very directional u Soft foot can produce an eccentric stator STATOR ECCENTRICITY SHORTED LAMINATIONS AND LOOSE IRON

28. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 Electrical line frequency.(FL) = 50Hz = 3000 cpm. Electrical line frequency.(FL) = 50Hz = 3000 cpm. 60HZ = 3600 cpm 60HZ = 3600 cpm No of poles. ( P) No of poles. ( P) Rotor Bar Pass Frequency (Fb) = No of rotor bars x Rotor Bar Pass Frequency (Fb) = No of rotor bars x Rotor rpm. Rotor rpm. Synchronous speed ( Ns) = 2xFL Synchronous speed ( Ns) = 2xFL P P Slip frequency ( F S )= Synchronous speed - Rotor rpm. Slip frequency ( F S )= Synchronous speed - Rotor rpm. Pole pass frequency (F P )= Slip Frequency x No of Poles. Pole pass frequency (F P )= Slip Frequency x No of Poles. Electrical line frequency.(FL) = 50Hz = 3000 cpm. Electrical line frequency.(FL) = 50Hz = 3000 cpm. 60HZ = 3600 cpm 60HZ = 3600 cpm No of poles. ( P) No of poles. ( P) Rotor Bar Pass Frequency (Fb) = No of rotor bars x Rotor Bar Pass Frequency (Fb) = No of rotor bars x Rotor rpm. Rotor rpm. Synchronous speed ( Ns) = 2xFL Synchronous speed ( Ns) = 2xFL P P Slip frequency ( F S )= Synchronous speed - Rotor rpm. Slip frequency ( F S )= Synchronous speed - Rotor rpm. Pole pass frequency (F P )= Slip Frequency x No of Poles. Pole pass frequency (F P )= Slip Frequency x No of Poles. FREQUENCIES PRODUCED BY ELECTRICAL MOTORS.

29. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ELECTRICAL PROBLEMS u Loose stator coils in synchronous motors generate high amplitude at Coil Pass Frequency u The coil pass frequency will be surrounded by 1X RPM sidebands SYNCHRONOUS MOTOR (Loose Stator Coils)

30. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ELECTRICAL PROBLEMS u Phasing problems can cause excessive vibration at 2F L with 1/3 F L sidebands u Levels at 2F L can exceed 25 mm/sec if left uncorrected u Particular problem if the defective connector is only occasionally making contact POWER SUPPLY PHASE PROBLEMS (Loose Connector)

31. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ELECTRICAL PROBLEMS u Eccentric rotors produce a rotating variable air gap, this induces pulsating vibration u Often requires zoom spectrum to separate 2F L and running speed harmonic u Common values of F P range from 20 - 120 CPM ECCENTRIC ROTOR ( Variable Air Gap ) ECCENTRIC ROTOR ( Variable Air Gap )

32. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ELECTRICAL PROBLEMS u DC motor problems can be detected by the higher than normal amplitudes at SCR firing rate u These problems include broken field windings u Fuse and control card problems can cause high amplitude peaks at frequencies of 1X to 5X Line Frequency DC MOTOR PROBLEMS

33. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ELECTRICAL PROBLEMS u 1X, 2X, 3X, RPM with pole pass frequency sidebands indicates rotor bar problems. u 2X line frequency sidebands on rotor bar pass frequency (RBPF) indicates loose rotor bars. u Often high levels at 2X & 3X rotor bar pass frequency and only low level at 1X rotor bar pass frequency. ROTOR PROBLEMS

34. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ROTOR BAR FREQUENCIES (SLOT NOISE) POLE MINIMUM POLE MAXIMUM MAX MIN

35. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 CALCULATION OF GEAR MESH FREQUENCIES CALCULATION OF GEAR MESH FREQUENCIES 20 TEETH 51 TEETH 1700 RPM 31 TEETH 8959 RPM -- HOW MANY TEETH ON THIS GEAR?

36. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 GEARS NORMAL SPECTRUM u Normal spectrum shows 1X and 2X and gear mesh frequency GMF u GMF commonly will have sidebands of running speed u All peaks are of low amplitude and no natural frequencies are present 14 teeth 8 teeth GMF= 21k CPM 2625 rpm 1500 rpm

37. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 GEARS TOOTH LOAD u Gear Mesh Frequencies are often sensitive to load u High GMF amplitudes do not necessarily indicate a problem u Each analysis should be performed with the system at maximum load

38. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 GEARS TOOTH WEAR u Wear is indicated by excitation of natural frequencies along with sidebands of 1X RPM of the bad gear u Sidebands are a better wear indicator than the GMF u GMF may not change in amplitude when wear occurs 14 teeth 1500 rpm 8 teeth 2625 rpm GMF = 21k CPM

39. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 GEARS GEAR ECCENTRICITY AND BACKLASH u Fairly high amplitude sidebands around GMF suggest eccentricity, backlash or non parallel shafts u The problem gear will modulate the sidebands u Incorrect backlash normally excites gear natural frequency

40. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 GEARS GEAR MISALIGNMENT u Gear misalignment almost always excites second order or higher harmonics with sidebands of running speed u Small amplitude at 1X GMF but higher levels at 2X and 3X GMF u Important to set Fmax high enough to capture at least 2X GMF

41. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 GEARS CRACKED / BROKEN TOOTH u A cracked or broken tooth will generate a high amplitude at 1X RPM of the gear u It will excite the gear natural frequency which will be sidebanded by the running speed fundamental u Best detected using the time waveform u Time interval between impacts will be the reciprocal of the 1X RPM TIME WAVEFORM

42. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 D0D0 D1D1 DBDB Note : shaft turning outer race fixed F = frequency in cpm N = number of balls BPFI = BPFO = BSF = FTF = Nb2Nb2 P d 2B d 1212 ( ( BdPdBdPd COS RPM ( ( 1 - 1 + COS X Nb2Nb2 ( 1 - BdPdBdPd ( X RPM ( ( 1 - BdPdBdPd ( COS 2 ( XRPM BdPdBdPd X

43. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ROLLING ELEMENT BEARINGS STAGE 1 FAILURE MODE u Earliest indications in the ultrasonic range u These frequencies evaluated by Spike Energy TM gSE, HFD(g) and Shock Pulse u Spike Energy may first appear at about 0.25 gSE for this first stage gSE ZONE BZONE AZONE CZONE D

44. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ROLLING ELEMENT BEARINGS STAGE 2 FAILURE MODE u Slight defects begin to ring bearing component natural frequencies u These frequencies occur in the range of 30k-120k CPM u At the end of Stage 2, sideband frequencies appear above and below natural frequency u Spike Energy grows e.g. 0.25-0.50gSE ZONE A ZONE BZONE CZONE D gSE

45. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ROLLING ELEMENT BEARINGS STAGE 3 FAILURE MODE u Bearing defect frequencies and harmonics appear u Many defect frequency harmonics appear with wear the number of sidebands grow u Wear is now visible and may extend around the periphery of the bearing u Spike Energy increases to between 0.5 -1.0 gSE ZONE AZONE BZONE CZONE D gSE

46. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 ROLLING ELEMENT BEARINGS STAGE 4 FAILURE MODE u Discreet bearing defect frequencies disappear and are replaced by random broad band vibration in the form of a noise floor u Towards the end, even the amplitude at 1 X RPM is effected u High frequency noise floor amplitudes and Spike Energy may in fact decrease u Just prior to failure gSE may rise to high levels gSE ZONE AZONE BZONE C High just prior to failure

47. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 GEARS HUNTING TOOTH u Vibration is at low frequency and due to this can often be missed u Synonymous with a growling sound u The effect occurs when the faulty pinion and gear teeth both enter mesh at the same time u Faults may be due to faulty manufacture or mishandling f Ht = (GMF)Na ( T GEAR)( T PINION)

48. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 OIL WHIP INSTABILITY u Oil whip may occur if a machine is operated at 2X the rotor critical frequency. u When the rotor drives up to 2X critical, whirl is close to critical and excessive vibration will stop the oil film from supporting the shaft. u Whirl speed will lock onto rotor critical. If the speed is increased the whip frequency will not increase. oil whirl oil whip

49. Efftek Diagnostic Engineers St. James House, Temple Sowerby, Cumbria, CA10 1RS, United Kingdom. +44(0)1768362866 OIL WHIRL INSTABILITY u Usually occurs at 42 - 48 % of running speed u Vibration amplitudes are sometimes severe u Whirl is inherently unstable, since it increases centrifugal forces therefore increasing whirl forces