chapter 1basic of rotating machinery vibration .pptx

basic of rotating machinery vibration

1. “ B as i c s of Rotat i ng Mach i n er y V ibr at i o n s CH APTE R 1 ”

2. I n t r oduction Th e vi b r a t io n o f the r o t a t in g m a c hiner y c o nt a i n s hu g e a mou n t o f in f or m a t io n th a t c an b e ut i li z ed t o de t er mine the m a c hin e c ond i t ion , the f a ul t p r odu c in g the dyn a mi c f o r c es th a t c a us es these v ib r a t ion s a n d the s e v er i ty o f these f a ul ts. 2

3. W h y s tudying Vib ra tion? Ass e ss th e c on di t i o n o f a ma ch i ne. D ia gn o se th e roo t c a u s e s o f a n y e x ce ssi v e vi b r a t i on if a n y . 3

4. Wh a t is Vib ra tion? Ba c k a n d f o r t h m o v e m e n t o r o s c ill at i o n o f a n y b od y . Th is o s c ill at i o n occu r s a rou nd th e bo dy equilibri um po s i t i o n. 4

5. 5 Vib r a tion Motion Pos iti on 1 M E qu ili b r i u m Pos iti o n K Pos iti on 2 O sc ill a to r y ( V ib ra to r y ) Motion

6. Wh a t c a u se s vi b ra tion ? 6 S y s t em Pa r a m e t e r s Rotating M a c hine M odel  S y s t e m Input ( D y na mic f or c e ) S y s t e m Output ( V ib r a ti on )

7. Wh a t c a u se s Vib ra tion ? ( c o n t ’ d.) 7

8. Sou r c e s of E x citing F o r c e s Ina d eq u a t e des i gn: F l e x ibili ty F l o w pul s a t i o n s Ma n u f actu r i ng d e f ect s : Ca s t in g ca v i t ie s le ad t o unb a l a n ce B e n t s h aft a n d e c ce n tr i c i ty P o o r i n s t a ll a t i o n : M i sa lign m e n t D i sto rt i o n ( s o ft foo t) P ipin g s t r a i n 8

9. Sou r c e s of E x citing F o r c e s ( c o n t ’ d.) Ab n o r mal o p e r a t i ng co n d i t i o n s ( b ey o n d des i gn p o i n t) C a v i t a t i o n R e c i r c ul a t i o n Lack of p r o p er ma i n t ena n ce R epl ac e m e n t o f p arts Ba l a n c in g & a lign m e n t Lub r i ca t i o n 9

10. Ca use & E f f e ct Anal y s is ** F O R C E N O T S P E E D ** 10 D y n a mic f o r c e ( Ca u se ) Reac ti on f o r ces Reac ti on f o r ces

11. Spinn i ng & Wh i r l ing 11 S p in n ing on ly m o ti o n S p in n ing & W h i r li n g m o ti o n Vi b r a t i on

12. Mot i on A nal y s is 12 M otion A na l y s i s of Unba l anced Rotor

13. Motion A nal y s is ( c o n t ’ d.) 13

14. Vib ra tion Me as u re s Thre e m e as ure s; d is p la ce m e n t , v e l oc i t y a n d a cce le r a t i o n. D i s p la ce m e n t is re l a t e d t o the m ot i o n. Th e v e l oc i t y is re l a t e d t o f a t igu e . Th e a cce le r a t i o n is d i rect ly prop orti on al t o th e f orce . 15

15. Me as u re s R e l a tionship 16 Table (1 . 1) Vibration M easur e s Re l ations h ip For har m onic ( sine) w a ve only: Displa c ement ( d )= D s i n (  t) Veloci t y ( v ) = d ( d ) = D  cos (  t) dt A cceleration (a)= d ( v ) = d t dt 2 d 2 ( d ) = - D  2 sin (  t) W he re “D” is the ma gn itude o f t he displac em ent si g nal, “  ” i s the an g u l ar r ate in rad/s a n d “t” is t h e time.

16. Me as u re s R e l a tionship ( c o n t ’ d.) 17

17. T ypic a l Un i ts The typi c al u n i ts f o r the d isp l ac e me n t, v elocity a n d acce l e r a tion a r e  m (mic r o ns), m m / s and g ’ s r especti v el y . T h e mic r on e quals 0.001 mm a nd g e quals 9.81 m / s 2 . 18

18. Num er i c a l E x a mp l e 19 The A m p li t ude / Phase R e l a t i onsh i p B e t w een t he Th r ee Vi b r a t i on M easu r es Displacement (sine w a v e) V elocity (cosine w a v e) A ccele r ation (minus sine w a v e) Am plitu de= 50  m F r e q u e n cy = 50 Hz A mpli t ude= 2  (50) (0 . 005) = 15 . 7 mm / s A m plit ude= 2  (50) (15.7) = 4929.8 mm/s 2 = 4.929 m/s 2 = 0.5 gs

19. 20 D/ V / A Sp e ct r a

20. Me as u res ’ P ha s e R e l a tionship A cce le r a t i o n leads v e l oc i t y by 9 degree s a n d leads d is p la ce m e n t b y 18 degree s. In othe r w ord s , d is p la ce m e n t lags v e l oc i t y by 90 degree s a n d lags a cce le r a t i o n b y 18 degree s. * * W e ne e d t o accele r a t e the body t o gi v e i t v eloci ty t o r e ach a di s t ance * * 21

21. Me as u re s Co n v e r s ion I n t eg r a tion a n d d i f f e r e n ti a tion i s theo re ti c al l y av ai l a b l e. P r act i c al l y i n t eg r a tion o n l y i s al l o w e d . Noise i s a c o ns i de r a tion . 22

22. Waves type Impulsive wave Harmonic wave Periodic wave Impact wave Random wave

23. 24 H ar mon i c v s . P er i od i c w a v e

24. I mpu l s i v e W a v e 25

25. 26 I m pact i ng

26. 27 R a ndom

27. Signal Cha r a c t er i s tics F req u ency : H o w ma n y c y c les pe r u nit t im e . R ec ip ro c al o f per i o d. Un i t s: Hz, CPM & O r de r s 28

28. 29 F r e quency & P er i od R e l a tionship

29. 30 P er i od i c W a v e f orm

30. Amp l itude D e t e ction M e thods ( F orm a t s ) 31 Sou r c e: Or b it s M agaz i n e

31. RMS A n al o g c al cu l a t i o n o f th e R MS Cal cu l a t i o n f ro m Sp ect rum d igi t ally 32 n v  v  ....  v v  2 n RMS 2 1 2 2

32. Sou r c e s of Co n f l icts D i s si m il a r i nputs D i s si m il a r signa l p r oce s sing pr ior t o a m plitude de t ect i on D i s si m il a r a m plitude de t ect i o n a l g or ith m s C a li b r a tion/ i nd i c a tion p r ob l ems 33 S o ur c e : Or b it s M a g a zin e

33. D e t e ctions Co n v e r s ion 34 Table ( 1 . 3) Am p litu d e Detectio n s Co n v ers i on For Har m onic ( Sine) Wave O nly: RM S= 0.707 P e ak Peak= 1 . 4 1 4 RM S Peak - to -P eak= 2 P e ak

34. P ha s e 35 P h a se Shift A i s lead i n g B

35. P ha s e 36

36. In & out of pha s e 37 In P h as e P ha se o r t ime d i f feren ce O u t o f P h as e

37. P ha s e meas u reme n ts m e thods Pho t oe le ct ric o r las e r probe s. [A b s o lu t e Phas e ] St r ob e lig h t . [Obs o le t e ] Du al ch a nne l a n al y z e r . [ R e l a t i v e Phas e ] K e y p has o r . [A b s o lu t e Phase f o r T u r bo m a ch i nery] 38

38. 39 K e y Pha s or f or Ex t erna l T r ig g er i ng

39. L a s e r of P ho t oelectric P r obes f or 40 Ex t erna l T r ig g er i ng

40. Ex t e rna l T r i g g e r i ng f or A b s olu t e P ha s e Me as u re m e n t T  41  T  360 o   Ta cho of Key P h a sor P ul s es

41. 42 Sy s t e m P a r a m e t e r s

42. Sys t em P a r a m e t e r s M ass St i f fn e ss D am p i ng 43

43. Ma s s  M ass is th e v o lume o f th e s y s t e m m u l t iplied b y the den s i t y o f i t s m a t e rial a n d th e t ypi c al u nit o f the mass is k il o g r ams ( kg ) .  Th e h igh e r th e mass th e l o w e r th e vi b r at i o n f o r the same f orc e am p li tu de a p plied.

44. Stiffne s s  St i f fn e ss is a m e as ur e o f th e s y s t e m e la st i c i t y a n d is d e f i ne d as th e d e f l ect i o n c a u s e d b y a p plyi n g u nit f orc e t o th e s y s t e m.  St i f fn e ss is t ypi c ally e xpre ss e d in New t o n pe r m e t e r (N/m).  Th e h igh e r th e st i f fn e ss, th e l o w e r th e vi b r at i on am p li tu d e s re s u l t e d f ro m same f orc e a p plied.

45. D a mp i ng  D am p i n g is d e f i ne d as th e a b ili t y o f th e s y s t e m t o d issip a t e ener gy i n t o he a t (i .e . c o n v e rts th e k in et ic ener gy o f m ot i o n o r vi b r at i o n i n t o he a t ener gy).  Th e d a m p i n g is e xpre ss e d in New t o n pe r millim e t e r pe r s e c on d (N/mm / s).  Th e h igh es t th e d a m p i n g in th e s y s t e m, th e l o w e r th e vi b r at i o n am p li tu de f o r th e same f orce .

46. N a tu r a l F re quency Whe r e :  n : natu r al f req u enc y ( r a d / s) k : st i f fn e ss (N/m) m: mass ( k g)

47. R es onance  R e s on a nc e is a c on di t i o n a t which th e f req u enc y of on e o f th e e x c i t ing f orce s is c l o s e o r eq ual t o on e of th e natu r al f req u enc i e s o f th e s y s t e m.  In th is c as e , th e s y s t e m will vi b r a t e s e v ere ly sin c e th e s y s t e m will w o rk as an am p lifier tha t c o n v e rts a l l ener gy i n t o vi b r a t o ry m ot i o n.  T he t e rm " r e son a nc e " is t ypi c ally u s e d wi t h st ru cture s; when d is cu s sing th e natu r al f req u enc i e s of a r o t o r , t he t e rm "C ri t i c al “p ee d" is t ypi c ally u s e d.

48. R es onance  R el at ed t o s tr uc t u r es.  De p e nd s o n m ass a n d s ti f fnes s.  S y s t em a c ts as a mp lifie r . 49 100 Hz b y 50 Hz 100 Hz b y 100 Hz 10 Hz b y 20 Hz V id eo : G r oun d T e s t V i deo : B r i dg e

49. Cr i ti c a l Sp ee ds  Th e c ri t i c al s peed s a r e th e s peed s a t which an e x c i t ing f orc e f req u enc y is v e ry c l o s e o r eq uals t o on e o f th e ro t o r natu r al f req u enc i e s.  In othe r w ord s , th e c ri t i c al s pee d is th e s pee d a t whi c h th e re s on a nc e occu r s in th e ro t o r . F o r e a c h c ri t i c al s peed , ther e is a u niq u e d e f l ect i o n s h a p e of t he r o t or known as "Mod e “h ape " .

50. Mode Sh a pes 51

51. 3D Mode Sh a pes 52 Link t o Vi d eo

52. 53 Que s tions ??