Ground vibration measurement near Sr. VP office area by shv46529

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									               Gr ou n d vi br at i on m eas u r em en t n ear S r .VP of f i ce ar ea

H is t or y:

Cu s t om er com pl ain s t h at all t h e ex ecu t i ves s it t in g i n an d ar ou n d S r .Vice
P r es iden t ’s of f ice w er e f eel in g vibr at ion s on t h e t able as w ell as on t h e f loor .

Gr ou n d Vibr at ion Meas u r em en t at of f ice ar ea:

Vibr ation meas ur ement (velocity vibr ation in mm/s ec) was car r ied out at s elected
locations on the identified floor ar ea and cubical tables (Refer layout) in differ ent
dir ections . All the meas ur ed data ar e Four ier analys ed to get the fr equency s pectr um.
T able- 1 s hows the vibr ation levels at var ious locations .

                        F loor L ayou t at 1 s t f loor of f ice ( T op View ) : -


                I                    II                              III                    IV


                1                     3                              5                      6


                2                     4                              6                      7




                     L ayou t of t h e bu ildi n g ( F r on t s ect ion al Vi ew ) : -


                             Ai r H an dl in g U n i t s




                                     S r .Vice P r es i den t Of f ice Ar ea




                                                                   Mai n t en an ce an d Qu al it y
               T ool R oom                                                     Of f ice




                                 T o As s em bl y                      AI R
                                      Ar ea                         CU R T AI N
              T able-1 Vi br at ion levels in velocit y at var iou s l ocat ion s
    ( W it h A/ C cu r t ain s in ‘ON ’ con dit ion & t op AH U f an s in ‘OF F ’ con dit ion )

                                  Vibr ation s ever ity level in mm/s ec (r ms .)
          Meas . Point No’s .               Meas ur ement Dir ection
                                        X                  Y              Z
              Location 1             0.94               1.02            0.98
              Location 2             0.08               0.09            0.08
              Location 3             1.18               1.21            1.16
              Location 4             0.17               0.19            0.13
             L ocat ion 5            1 .2 3             1 .6 1         1 .3 4
             L ocat ion 6            0 .1 7             0 .3 1         0 .1 5
              Location 7             1.10               1.32            1.26
              Location 8             0.09               0.10            0.08

Meas u r em en t :

•   T he gr ound vibr ation meas ur ement was done us ing DI 2200 FFT vibr ation analys er
    and the low fr equency high s ens itivity acceler ometer at s elected locations in the
    office ar ea.
•   T he meas ur ement was car r ied out initially by s witching off all the top AHU’s (6
    no’s ) which was located in the 2 nd floor of the building and the fr equency
    s pectr ums wer e obs er ved
•   I t was evident fr om the meas ur ement that the vibr ation levels wer e alar ming at
    location 5 and 6 compar ed to all the other ar eas .
•   S o a mor e detailed meas ur ement and s pectr um analys is was done at the above
    s aid locations by applying cer tain conditions like taking the meas ur ement by
    s witching off and on cer tain machines which wer e located in the gr ound floor
    (r efer s pectr um # 1 and 2)
•   I t was obs er ved fr om the meas ur ement that a fr equency component at 23.8 Hz
    was pr edominant (with high vibr ation value of 1.56 mm/s ec) in the s pectr um
    compar ed to all the other fr equency peaks
•   Als o it was obs er ved that when the A/C cur tain fan pr ovided on the output s ide of
    the as s embly r oom was s witched off ther e wer e no vibr ations felt at locations 5
    and 6.
•   When the vibr ation meas ur ement was taken on this A/C cur tain fan it was found
    that at 23.8 Hz (r unning fr equency of this fan) was s howing as high as 18 mm/s ec
    (r efer s pectr um no. # 3) which is an unbalanced induced vibr ation and its r elated
    har monics . Als o the vibr ation was ver y much felt on the walls adj acent to this fan.
•   I t was obs er ved fr om the meas ur ement that the vibr ation levels wer e incr eas ed to
    1.91 mm/s ec fr om 1.61 mm/s ec at the above s aid locations when all the 6 top
    AHU fans wer e s witched on.
S pect r u m # 1 , Meas u r em en t L ocat ion # 5 ( cu bi cal N o. 3 ) – on t h e t abl e


                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) on – Top AHU (old) off

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) off – Top AHU (old) on

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) on – Top AHU (old) on

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) off – Top AHU (old) off

                                            Dynamic Testing machines on - A/C Curtains off –
                                            A/C Blowers on - Top AHU (new) off – Top AHU (old) off

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers off - Top AHU (new) off – Top AHU (old) off




S pect r u m # 2 , Meas u r em en t L ocat ion # 6 ( cu bi cal N o. 3 ) – on t h e f loor

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) on – Top AHU (old) off
                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) off – Top AHU (old) on

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) on – Top AHU (old) on

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers on - Top AHU (new) off – Top AHU (old) off

                                            Dynamic Testing machines on - A/C Curtains off –
                                            A/C Blowers on - Top AHU (new) off – Top AHU (old) off

                                            Dynamic Testing machines on - A/C Curtains on –
                                            A/C Blowers off - Top AHU (new) off – Top AHU (old) off
             S pect r u m # 3 , Meas u r em en t L ocat ion on A/ C cu r t ain f an


            2 3 .8 H z – R u n n i n g f r equ en cy




Con cl u s ive R em ar ks :

•   I t is evident fr om the meas ur ement that the vibr ation levels on the Cubical tables
    and on the floor in the 1 s t floor office ar e mor e than the per mis s ible limits
    (vibr ation levels s hould be les s than 0.1 mm/s ec on the floor )
•   T he A/C cur tain pr ovided on the output s ide of the as s embly hall is giving high
    vibr ations which is getting tr ans mitted to the adj acent walls and then to the 1 s t
    floor office. T his needs to be cleaned on r egular bas is and dus t getting
    accumulated on this fan s hould be contr olled.
•   All the 6 top AHU fans ar e als o having high vibr ations and ar e contr ibuting for
    incr eas ing in vibr ation levels in the office ar ea. T hes e fans need immediate
    attention.
•   T he above cor r ective actions has to be taken at the ear lies t els e in a long r un
    thes e vibr ations may have s ome adver s e effect on the building s tr uctur e.

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