appendix b. chapter 11. fan housing vibration caused by
TRANSCRIPT
Fan
Hou
sing
Vib
ratio
n C
ause
d by
Res
onan
ce
App
licat
ion
of M
odal
& V
ibra
tion
Ana
lysi
s
Ken
Sin
glet
onK
SC
Con
sulti
ng L
LC
App
endi
x B
. Cha
pter
11.
KS
C C
onsu
lting
LLC
Fou
r F
D fa
ns w
ere
inst
alle
d at
the
site
to m
eet e
nviro
nmen
tal
requ
irem
ents
of t
he p
roce
ss.
Bac
kgro
und
The
fan
desi
gn d
etai
ls w
ere
as
follo
ws:
•15
00 H
P D
irect
Driv
e A
MC
A A
rran
gem
ent
8
•In
let G
uide
Van
e C
ontr
ol
•S
pher
ical
Rol
ler
Bea
rings
, Gre
ase
Lubr
icat
ed
•P
LC M
onito
ring
and
Con
trol
11B
-1
Fig
ure
1. S
chem
atic
of F
an w
ith s
ome
Par
amet
ers
Labeled
Gas
Tem
p13
0 de
gree
s F
Win
ter
250
degr
ees
F S
umm
er
Max
. Thr
ust
Load
320
9 lb f
Flo
w 3
63,7
94 A
CF
M
8042
lbf
1888
lbf
SK
F 2
2236
C
CK
/W33
SK
F 2
2232
C
CK
/W33
1560
HP
, 119
4 R
PM
11B
-2
Bac
kgro
und
The
fans
exp
erie
nced
man
y re
liabi
lity
prob
lem
s du
ring
th
e 1
stye
ar o
f ope
ratio
n. T
hese
pro
blem
s in
clud
ed:
•B
earin
g fa
ilure
s on
eac
h fa
n
•A
cat
astr
ophi
c be
arin
g fa
ilure
on
#1 F
an r
esul
ting
in a
bro
ken
mot
or s
haft
and
dam
aged
fan
shaf
t, w
hich
requ
ired
rep
lace
men
t.
•H
igh
bear
ing
oper
atin
g te
mpe
ratu
res.
•S
ever
al lu
bric
atio
n gr
ease
s w
ere
trie
d in
clud
ing
vary
ing
quan
tity
and
inte
rval
of g
reas
ing
as w
ell a
s gr
ease
rem
oval
from
the
bear
ing
hous
ings
.
•A
sm
all o
il re
circ
ulat
ion
syst
em w
as in
stal
led
on o
ne
fan,
but
onl
y pr
ovid
ed m
ixed
res
ults
•C
ompo
nent
fatig
ue fa
ilure
s of
dis
char
ge v
ane
asse
mb
ly,
11B
-1
Initi
al A
sses
smen
tT
he in
itial
ass
essm
ent o
f the
fans
was
mad
e in
Dec
20
01.
Num
erou
s de
ficie
ncie
s w
ere
iden
tifie
d:
•T
he F
an E
nd B
earin
g w
as o
pera
ting
at 9
2% o
f max
imum
re
com
men
ded
spee
d w
ith g
reas
e lu
bric
atio
n.
•F
an h
ousi
ng h
igh
ampl
itude
vib
ratio
n (a
cces
s to
hou
sing
lim
ited
by in
sula
tion.
)
•T
he d
isch
arge
van
e ho
usin
gs e
xhib
ited
high
leve
ls o
f vi
brat
ion
and
crac
king
of w
elds
at t
he li
nkag
e/sh
aft i
nter
face
s.
•V
ibra
tion
anal
ysis
indi
cate
d lu
bric
atio
n-re
late
d hi
gh e
nerg
y vi
brat
ion
(CS
I Pea
kVue
data
) ca
used
by
bear
ing
rolle
r sk
iddi
ng(B
earin
g lo
ad le
ss th
an s
peci
fied
min
imum
load
.)
•T
he s
pher
ical
rol
ler
bear
ings
cal
cula
ted
to b
e m
arg
inal
for
grea
se lu
bric
atio
n fo
r th
e fa
n op
erat
ing
spee
d of
119
4 R
PM
. 11B
-2
Initi
al R
ecom
men
datio
ns in
clud
ed th
e fo
llow
ing:
Initi
al A
sses
smen
t
•P
erfo
rm a
mod
al te
st o
f one
fan
hous
ing.
•C
hang
e be
arin
g lu
bric
ant f
rom
gre
ase
to o
il an
d In
sta
ll an
oil
re-c
ircul
atin
g sy
stem
with
filte
ring
and
tem
pera
tur
e co
ntro
l (T
he fa
n en
d be
arin
gs w
ere
oper
atin
g at
92%
of r
ecom
mende
d m
axim
um s
peed
with
gre
ase
lubr
icat
ion
(bor
derli
ne fo
r gr
ease
; thi
s de
sign
trul
y ne
eded
oil
lubr
icat
ion)
.
11B
-2
Fig
ure
2.O
vera
llV
ibra
tion
(in/s
ec)o
fFan
#4H
ousi
ngM
easur
edP
riort
oS
tart
upof
the
Fan
and
Dur
ing
Inle
tGui
deVa
neA
djus
tmen
tsto
Ful
lOpe
n,C
lose
dand
Shu
tDow
n.
Vib
ratio
n lo
wes
t lev
el a
t 30%
to
70%
gui
de v
anes
ope
n.
Gui
de V
ane
setti
ngs
adju
sted
in 1
0% s
teps
.
Dur
ing
seco
nd v
isit
to s
ite F
eb 2
002
. B
earin
g &
fan
hous
ing
vibr
atio
n w
as m
easu
red.
A s
ingl
e ac
cele
rom
eter
was
atta
ched
to
the
fan
hous
ing
thou
gh a
hol
e dr
illed
in th
e in
sula
tion.
Min
imum
1.2
in/s
ec w
as p
rese
nt.
Inle
t Van
es 1
00%
11B
-3
Inle
t Gui
de V
anes
Clo
sed
Fan
Sta
rtup
Fig
ure
3. F
an #
4 H
ousi
ng V
ibra
tion
Spe
ctru
m. M
ost V
ibra
tion
Ene
rgy
was
at a
bout
20
Hz
(12
00 C
PM
), o
r 1
X F
an R
unni
ng S
peed
(2.
5 in/sec
).
T
he R
espo
nse
App
eare
d to
be
Cau
sed
by R
eson
ance
of
the
Hou
sing
.
Bro
ad B
ase,
Indi
cato
r of
Res
onan
ce
(at F
an S
peed
of 1
194
RP
M)
Fre
quen
cy S
pect
rum
in F
ebru
ary
2002
on
Fan
#4
Hou
sing
11B
-4
Illus
trat
ion
A. O
verv
iew
of S
crub
ber
Fan
s E
valu
ated
Fan
Insp
ectio
n A
fter
Insu
latio
n R
emov
ed•
Rec
omm
enda
tion
to p
erfo
rm fa
n ho
usin
g m
odal
test
wa
s ac
cept
ed
and
sche
dule
d fo
r S
ept 1
1-12
, 200
2.
•In
sula
tion
was
re
mov
ed to
pro
vide
ac
cess
to th
e fa
n ho
usin
g.
•T
he fa
n ho
usin
g w
as
insp
ecte
d fo
r cr
acki
ng a
s w
ell a
s ge
nera
l des
ign
and
fabr
icat
ion
met
hods
.
•N
o cr
acks
wer
e fo
und.
13 F
eet
11B-
4
•T
he h
ousi
ng w
as a
thre
e pi
ece
desi
gn
to p
erm
it sh
ippi
ng a
nd r
emov
al o
f the
fa
n w
heel
.
•T
he tw
o up
per
sect
ions
wer
e bo
lted
to
the
low
er h
alf a
t the
cen
terli
ne a
nd to
ea
ch o
ther
at a
ver
tical
flan
ge.
Fan
Insp
ectio
n A
fter
Insu
latio
n R
emov
ed
Vert
ical
Spl
it
Hor
izon
tal S
plit
Fig
ure
5. F
an H
ousi
ng S
how
ing
Vert
ical
and
Hor
izon
tal
Join
ts a
nd In
ters
ectio
n N
ear t
he F
an C
ente
rline
11B
-5
It w
as le
arne
d th
at s
ectio
ns o
f the
hou
sing
fla
nges
(4
inch
Cha
nnel
) ha
d be
en r
emov
ed
usin
g a
cutti
ng to
rch
to p
rovi
de c
lear
ance
for
th
e sh
aft.
The
rem
oval
of t
hese
stif
fene
rs in
the
ce
nter
of t
he h
ousi
ng s
igni
fican
tly r
educ
ed th
e rig
idity
of t
he h
ousi
ng.
Fig
ure
4. T
he D
raw
ing
by th
e F
an O
EM
Indi
cate
s th
e V
ertic
al an
d H
oriz
onta
l Fla
nges
wer
e D
esig
ned
to b
e V
ery
Clo
se to
the
Sha
ft.
Ext
endi
ng L
ines fo
r th
e V
ertic
al a
nd H
oriz
onta
l F
lang
es
Indi
cate
Pot
entia
l Sha
ft In
terf
eren
ce.
11B
-5
Not
e F
an H
ousi
ng S
truc
tura
l M
embe
rs o
f 4”
Cha
nnel
Cut
w
ith T
orch
to P
rovi
de F
an S
haft
Cle
aran
ce.
11B
-5
Fig
ure
6.G
roov
e W
orn
In F
an
Sha
ft C
ause
d by
Con
tinuo
us
Con
tact
With
Rub
ber
Air
Sea
l.
Mod
al T
est
•19
5 Te
st m
easu
rem
ent p
oint
s (D
OF
) w
ere
laid
out
in
a m
esh
as
show
n in
the
phot
os.
•E
xcita
tion
was
by
impa
ct u
sing
a P
CB
Inst
rum
ente
d 1
2 lb
Sle
dge
Ham
mer
. 5
Acc
eler
omet
ers
wer
e ro
ved
to e
ach
DO
F.
Mitc
h F
ranc
e -
Layi
ng O
ut
Mod
al T
est P
oint
s on
Fan
H
ousi
ng, S
haft
Inle
t Sid
e
Fig
ure
7.
11B
-6
ME
’sco
peV
ES
Mod
el
11B
-7
Illus
trat
ion
B.
Driv
ing
Poi
nt
6X/6
X
ME
’sco
peV
ES
Mod
elD
OF
’s (
195
DO
F M
easu
red) 11
B-7
DO
F 45
X
Fig
ure
9. F
requ
ency
Res
pons
e F
unct
ion
(FR
F)
of H
ousing
Iner
tanc
e M
agni
tude
Plo
t (g/
lbf)
Driv
ing
Poi
nt F
requ
ency
Res
pons
e F
unct
ion
(FR
F)
tak
en o
n th
e fa
n ho
usin
g sh
owed
man
y N
atur
al F
requ
enci
es.
Fan
2X
The
re w
as a
ver
y re
spon
sive
nat
ural
freq
uenc
y at
12
90 C
PM
(21
.5 H
z)ne
ar
Fan
1X
run
ning
spe
ed, w
hich
turn
ed o
ut to
be
the
prim
ary
prob
lem
.
©C
opyr
ight
200
5: T
ech
nica
l Ass
ocia
tes
of C
harl
otte
P.C
.
Fan
1X
11B
-8
1290
CP
M
3300
CP
M
11B
-7
Fig
ure
10 s
how
s a
Spe
ctru
m ta
ken
on D
rivin
g P
oint
6X
with
the
fan
runn
ing.
Sho
wed
hig
h vi
brat
ion
of 1
.10
in/s
ec a
t 1 X
Fan
spe
ed o
n fa
n ho
usin
g.
Als
o sh
owed
a n
otab
le le
vel o
f .38
4 in
/sec
at 3
150
CP
M (
near
the
2nd
Mod
e id
entif
ied
in F
igur
e 9)
.
11B
-8
RO
UT
E W
AV
EFO
RM
1
2-S
ep-0
2 1
7:11
:52
P
K =
1.0
6
PK
(+) =
1.7
7
P
K(-
) = 2
.08
CR
ES
TF=
2.7
7
050
100
150
200
250
300
350
400
-3-2-1012
Tim
e in
mS
ecs
Velocity in In/Sec
One
- O
FF R
OU
TE
MA
CH
INE
OFF
RO
UT
E -O
RP
O
FF R
OU
TE
ME
AS
UR
EM
EN
T P
OIN
T D
AT
A
Labe
l: P
t 6X
Ste
el A
ngle
Rem
oved
RO
UT
E S
PE
CT
RU
M
12-
Sep
-02
17:
11:5
2
OV
ER
ALL
= 1.
38 V
-DG
P
K =
1.3
7
LO
AD
= 3
0.0
R
PM
= 1
190.
R
PS
= 1
9.83
010
000
2000
030
000
0
0.3
0.6
0.9
1.2
1.5
Freq
uenc
y in
CP
M
PK Velocity in In/Sec
Freq
: O
rdr:
S
pec:
315
0.0
2.
647
.3
84
1200
CP
M 1
.1 in
/sec
3150
CP
M .3
84 in
/sec
Fig
ure
10. V
ibra
tion
at D
OF
6X
whi
ch w
as th
e M
odal
Te
st D
rivin
g P
oint
Loc
atio
n.
Mos
t Vib
ratio
n w
as F
ound
at 1
200
and
3150
CP
M (2
0.0
and
52.
5 H
z).
Hz
0.0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
10E-3
1E-3
100E-6
10E-6
(9.06E-3@
191)
(10.3E-3@
195)
M#6 <6X+: 6X+> Trace 1
Fan
Hou
sing
Mod
e S
hape
s
The
hou
sing
was
mov
ing
in a
nd o
ut
perp
endi
cula
r to
the
shaf
t axi
s due
to
cut
stif
fene
rs.
1stC
ircul
ar M
ode
Sha
pe (
near
119
4 R
PM
fan
run
ning
spe
ed).
Max
vib
ratio
n. m
easu
red
durin
g th
e te
st w
as D
OF
8X a
t 1.7
2 ip
s(nea
r th
e fa
n ho
usin
g cu
tout
whe
re th
e sh
aft p
asse
s th
roug
h th
e ho
usin
g -
see
Illus
trat
ion
B).
Fig
ure
11. D
rivin
g P
t 6X
/6X
, Cur
sor
on 1
277
CP
M (
21.2
8 H
z) M
ode.
Fig
ure
12. M
ode
Sha
pe a
t 12
77 C
PM
(21
.28
Hz)
.
11B
-10
1277
CP
M (
21.2
8 H
z)
Thi
s C
ircu
lar
Mod
e w
as th
e P
rim
ary
Con
trib
utor
to F
an
Hou
sing
Vib
ratio
n.
DO
F
8
Hz
0.0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
10E-3
1E-3
100E-6
10E-6
(9.06E-3@
191)
(10.3E-3@
195)
M#6 <6X+: 6X+> Trace 1
Fan
Hou
sing
Mod
e S
hape
s
The
hou
sing
mot
ion
is o
ut o
f pha
se
on e
ach
side
of t
he h
ousi
ng
cent
erlin
e.
Dis
char
ge n
ozzl
e pa
rtic
ipat
es in
the
mod
e – f
atig
ue fa
ilure
of w
elds
.
Max
vib
ratio
n. m
easu
red
durin
g th
e te
st w
as D
OF
45 a
t 0.1
55 ip
s(s
ee
Illus
trat
ion
B).
Fig
ure
14. M
ode
Sha
pe a
t 24
49 C
PM
(40
.8 H
z) is
nea
r 2
X F
an S
peed
.
Fig
ure
13. D
rivin
g P
t 6X
/6X
, Cur
sor
on 2
449
CP
M (
40.8
Hz)
Mod
e.
11B
-11
2449
CP
M (
40.8
Hz)
DO
F
45
Hz
0.0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
10E-3
1E-3
100E-6
10E-6
(9.06E-3@
191)
(10.3E-3@
195)
M#6 <6X+: 6X+> Trace 1
Fan
Hou
sing
Mod
e S
hape
s
The
hou
sing
mot
ion
is o
ut o
f ph
ase
each
sid
e of
the
cent
erlin
e.
Dis
char
ge n
ozzl
e do
es n
ot
part
icip
ate
in th
e m
ode.
Max
vib
ratio
n. m
easu
red
durin
g th
e te
st w
as D
OF
45 a
t 0.4
55 ip
s.
Fig
ure
16. M
ode
Sha
pe a
t 32
99 C
PM
(55
.0 H
z). T
his
was
the
2ndM
ost R
espo
nsiv
e M
ode.
Fig
ure
15. D
rivin
g P
t 6X
/6X
, Cur
sor
on 3
299
CP
M (
55.0
Hz)
Mod
e.
11B
-12
3299
CP
M (
55.0
Hz)
DO
F
45
Hz
0.0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
10E-3
1E-3
100E-6
10E-6
(9.06E-3@
191)
(10.3E-3@
195)
M#6 <6X+: 6X+> Trace 1
Fan
Hou
sing
Mod
e S
hape
s
Prim
arily
pan
el c
ircul
ar m
ode
left
side
of h
ousi
ng.
Max
vib
ratio
n m
easu
red
durin
g th
e te
st w
as D
OF
45 a
t 0.1
0 ip
s.
Fig
ure
18. M
ode
Sha
pe a
t 47
13 C
PM
(78
.65
Hz)
. Not
e M
otio
n on
Lef
t Sid
e of
B
low
er H
ousi
ng.
Fig
ure
17. D
rivin
g P
t 6X
/6X
, Cur
sor
on 4
713
CP
M (
78.5
5) H
z M
ode.
11B
-13
4713
CP
M (
78.6
5 H
z)
DO
F
45
Hz
0.0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
10E-3
1E-3
100E-6
10E-6
(9.06E-3@
191)
(10.3E-3@
195)
M#6 <6X+: 6X+> Trace 1
Fan
Hou
sing
Mod
e S
hape
s
Prim
arily
pan
el c
ircul
ar m
odes
of
the
fan
hous
ing.
Max
vib
ratio
n m
easu
red
durin
g th
e te
st w
as D
OF
45 a
t 0.1
44 ip
s.
Fig
ure
20. M
ode
Sha
pe a
t 95
80 C
PM
(15
9.7
Hz)
. P
rimar
ily P
anel
Ben
ding
M
odes
of F
an H
ousi
ng.
Fig
ure
19. D
rivin
g P
t 6X
/6X
, Cur
sor
on 9
580
CP
M (
159.
7 H
z) M
ode.
11B
-14
9580
CP
M (
159.
7 H
z)
DO
F
45
Afte
r th
e M
odal
Tes
t, a
Tem
pora
ry 4
” x
4” A
ngle
was
Cla
mpe
d to
the
Fan
Hou
sing
an
d th
e F
an w
as R
esta
rted
.
Fig
ure
21. V
ibra
tion
was
Tak
en W
ith &
With
out t
he A
ngle
Atta
ched
to
the
Hou
sing
. 11B
-15
4”X
4”
Ang
le C
-C
lam
ped
to
Fan
H
ousi
ng
Cha
nnel
One
- O
FF R
OU
TE M
ACH
INE
OFF
RO
UTE
-OR
P v
s O
FF R
OU
TE -O
RP
Labe
l: P
t 6X
Ste
el A
ngle
Rem
oved
0
0.3
0.6
0.9
1.2
1.5
Com
paris
on S
pect
rum
O
FF R
OU
TE -O
RP
1
2-S
ep-0
2 1
7:11
080
0016
000
2400
0
0
0.3
0.6
0.9
1.2
1.5
Ref
eren
ce S
pect
rum
OFF
RO
UTE
-OR
P
12-
Sep
-02
16:
58
Freq
uenc
y in
CP
M
PK Velocity in In/Sec
Freq
: O
rdr:
Sp
2:
120
0.0
1.
008
1.
105
4 X
1/2
" A
ngle
Cla
mpe
d to
Hou
sing
No
angl
e cl
ampe
d to
hou
sing
1 X Fan
Fan
Run
ning
with
Tem
pora
ry 4
x 4
Ang
le c
lam
ped
to t
he fa
n ho
usin
g. V
ibra
tion
was
pre
dom
inan
tly a
t DO
F 6
X (
Illu
stra
tion
B).
No
Ang
le C
lam
ped
to
Fan
Hou
sing
(1.
1 ip
s)
4 x
4 x
½” A
ngle
C
lam
ped
to F
an
Hou
sing
(0.
45 ip
s)
Tem
pora
ry s
tiffe
ner
did
prov
e to
be
effe
ctiv
e in
re
duci
ng v
ibra
tion
11B
-15
Scru
bber
Fan
, Com
pars
ion
of H
ousi
ng V
ibra
tion
With
/With
out 4
X4 A
ngle
Stif
fene
r Cla
mpe
d To
Hou
sin
g 12
00 C
PM F
requ
ency
0.00
0
0.20
0
0.40
0
0.60
0
0.80
0
1.00
0
1.20
0
1.40
0
1.60
0
1.80
0
2.00
0
6X7X
8X45
X43
X78
X82
X66
X9X
10X
11X
69X
85X
Mea
sure
men
t Lo
cati
on
Angl
e St
iffe
ner C
lam
ped
To H
ousin
gN
o An
gle
Stif
fene
r Cla
mpe
d To
Hou
sing
Cha
rt 1
. Vib
ratio
n at
120
0 C
PM
Fre
quen
cy w
ith T
empo
rary
Ang
le C
lam
ped
to
Hou
sing
Act
ing
as a
Stif
fene
r (B
lue)
and
the
Ang
le
Rem
oved
(Y
ello
w).
(Sep
tem
ber 2
002)
11B
-16
Rec
omm
enda
tions
1. B
olt T
wo
4” x
4” A
ngle
to
the
hous
ing
abov
e th
e be
arin
gs to
co
ntro
l the
prim
ary
mod
e. U
se b
olte
d at
tach
men
t to
perm
it re
mov
al o
f the
hou
sing
sec
tion
for
fan
whe
el a
cces
s.
2. W
eld
a 4”
x 4
” Ang
le t
o th
e ho
usin
g be
low
the
cent
erlin
e to
hel
p co
ntro
l the
prim
ary
mod
e at
127
7 C
PM
(21
.28
Hz)
.
3. W
eld
½”
x 4”
Bar
stif
fene
rs to
con
trol
pan
el m
odes
.
Stif
feni
ng th
e fa
n ho
usin
g to
con
trol
the
prim
ary
res
onan
t am
plifi
catio
n at
127
7 C
PM
(21
.28
Hz)
was
the
maj
or
focu
s.
Str
uctu
ral s
teel
stif
fene
rs b
olte
d an
d w
elde
d to
the
hous
ing
wer
e pr
opos
ed a
s fo
llow
s:
11B
-17
4” x
½”
Pla
te S
tiffe
ners
w
elde
d to
the
hous
ing
and
exis
ting
angl
e.
Fan
Hou
sing
Stif
feni
ng
Rec
omm
enda
tions
.4”
x ½
” P
late
Stif
fene
rs w
elde
d to
the
hous
ing
and
exis
ting
angl
e.
Two
4” x
4”
piec
es o
f an
gle
wel
ded
to th
e ho
usin
g an
d ex
istin
g ch
anne
l.
Fig
ure
22.
Two
4” x
4”
x 86
” an
gle
bolte
d to
the
exis
ting
vert
ical
ang
le a
nd
chan
nel.
11B
-17
4 X
4 a
ngle
Bol
ted
to
Fan
Hou
sing
A s
ite v
isit
in D
ec 2
004,
two
year
s af
ter
the
mod
al te
st, p
rovi
ded
an
oppo
rtun
ity to
rec
heck
vib
ratio
n an
d th
e st
ruct
ural
mod
ifica
tions
that
w
ere
actu
ally
mad
e to
the
fan.
Fig
ure
23.
11B
-18
One
- S
crub
ber F
an F
our
Fan
4
-F2A
Fa
n O
utbo
ard
Axia
l
Labe
l: F
an H
ousi
ng A
xial
0
0.5
1.0
1.5
2.0
Com
paris
on S
pect
rum
Fa
n 4
-F
2A
07-
Dec
-04
11:
43
010
000
2000
030
000
0
0.5
1.0
1.5
2.0
Ref
eren
ce S
pect
rum
Fan
4
-F2A
2
7-Fe
b-02
10:
03
Freq
uenc
y in
CP
M
PK Velocity in In/Sec
Fig
ure
24. C
ompa
rison
of B
efor
e an
d A
fter
Vib
ratio
n S
pect
ra M
easu
red
on
Fan
#4
Hou
sing
, D
OF
6X
at F
an H
ousi
ng S
plit
Line
Str
uctu
ral M
embe
r.
Initi
al v
ibra
tion
mea
sure
d 1.
6 in
/sec
, pk
at 4
0% in
let g
uide
van
e se
tting
.
Afte
r an
gle
was
bol
ted
to th
e ho
usin
g, v
ibra
tion
was
redu
ced
to 0
.15
in/s
ec, P
k at
1X
, sho
win
g a
10.7
:1 r
educ
tion
(91%
dec
reas
e).
11B
-18
Afte
r C
orre
ctio
n
1X F
an (
0.15
in/s
ec)
Bef
ore
Cor
rect
ion
1X F
an (
1.6
in/s
ec)
One
- S
crub
ber F
an F
our
Fan
4
-F2A
Fa
n O
utbo
ard
Axia
l
Labe
l: F
an H
ousin
g Ax
ial
Anal
yze
Spe
ctru
m
0
7-D
ec-0
4 1
1:43
:35
PK
= .
3532
L
OAD
= 1
00.0
R
PM
= 1
194.
(19.
90 H
z)
040
0080
0012
000
1600
0
0
0.05
0.10
0.15
0.20
Freq
uenc
y in
CPM
PK Velocity in In/Sec
Freq
: O
rdr:
Sp
ec:
146
2.5
1.
225
.09
321
Fig
ure
25.
The
Hou
sing
Vib
ratio
n af
ter
Ang
le B
olte
d to
Hou
sing
. S
pect
rum
Sho
ws
the
Hou
sing
Nat
ural
Fre
quen
cy h
as In
crea
sed
from
App
roxi
mat
ely
1277
CP
M to
146
2 C
PM
(20
.0 to
24
.4 H
z).
Hou
sing
Res
onan
ce
Fan
1X
Run
Spe
ed
The
res
onan
ce is
stil
l ex
cite
d by
air
flow
; B
ut th
e am
plitu
de
was
redu
ced
to o
nly
abou
t 0.1
in/s
ec, p
k (w
as 0
.32
in/s
ec, p
k).
Initi
al F
an 1
X v
ibra
tion
mea
sure
d 1.
6 in
/sec
, pk
at 4
0% in
let g
uide
van
e se
tting
.
Afte
r an
gle
was
bol
ted
to th
e ho
usin
g, v
ibra
tion
was
redu
ced
to 0
.15
in/s
ec, P
k at
1X
,sh
owin
g a
10.7
:1 r
educ
tion
(91%
decr
ease
).
11B
-19
One
- S
crub
ber F
an F
our
Fan
4
-F2A
Fa
n O
utbo
ard
Axia
l
Labe
l: F
an H
ousin
g Ax
ial
Anal
yze
Spe
ctru
m
0
7-D
ec-0
4 1
1:43
:35
PK
= .
3532
L
OAD
= 1
00.0
R
PM
= 1
194.
(19.
90 H
z)
040
0080
0012
000
1600
0
0
0.05
0.10
0.15
0.20
Freq
uenc
y in
CPM
PK Velocity in In/Sec
Freq
: O
rdr:
Sp
ec:
146
2.5
1.
225
.09
321
Fig
ure
25.
The
Hou
sing
Vib
ratio
n af
ter
Ang
le B
olte
d to
Hou
sing
. S
pect
rum
Sho
ws
the
Hou
sing
Nat
ural
Fre
quen
cy h
as S
hift
ed
from
App
roxi
mat
ely
1277
CP
M to
146
2 C
PM
(21
.3 to
24
.4 H
z).
Hou
sing
Res
onan
ce
Fan
1X
Run
Spe
ed
The
res
onan
ce is
stil
l pre
sent
but
is s
hifte
d 14
.5%
hig
her
in fr
eque
ncy
away
from
fa
n ru
nnin
g sp
eed.
Afte
r m
odifi
catio
ns, t
he M
ode
mea
sure
d 14
62 C
PM
or
22.0
% fr
om F
an 1
X. P
rior
to
mod
ifica
tions
, the
Mod
e m
easu
red
1277
CP
M o
r 6.
5% f
rom
Fan
1X
.
11B
-19
Hou
sing
Nat
ural
F
requ
ency
Shi
fted
from
12
77 to
146
2 C
PM
.
1.T
he v
ibra
tion
and
mod
al t
est d
ata
conf
irmed
the
susp
ecte
d st
ruct
ural
res
onan
ces
of th
e fa
n ho
usin
g.
2.D
urin
g or
igin
al in
stal
latio
n of
the
fans
, the
mati
ng jo
int f
lang
es a
t the
cen
ter
of
the
hous
ing
had
been
rem
oved
by
a cu
tting
torc
h to
pr
ovid
e cl
eara
nce
for
the
shaf
t. T
he r
emov
al o
f the
se s
tiffe
ners
sig
nific
antly
redu
ced
rigid
ity o
f the
sha
ft en
try
side
of t
he fa
n ho
usin
g.
3.M
ost h
ousi
ng v
ibra
tion
resp
onse
was
at f
ive
natu
ral f
requ
enci
es –
1277
, 244
9,
3299
, 471
3 an
d 96
00 C
PM
. E
xcita
tion
of th
e 12
77 C
PM
mod
e w
as th
e pr
imar
y co
ntrib
utor
to
hous
ing
vibr
atio
n. T
he 3
299
CP
M m
ode w
as th
e 2nd
mos
t re
spon
sive
.
4.D
urin
g th
e m
odal
tes
t, th
e in
abili
ty to
isol
ate
the fa
n fr
om a
ir le
akag
e ca
used
si
gnifi
cant
hou
sing
vib
ratio
n. T
his
back
grou
nd v
ibrat
ion
mad
e it
mor
e di
fficu
lt to
obt
ain
high
qua
lity
mod
al t
est d
ata.
A m
ediu
m sle
dge
mod
al h
amm
er w
as to
o sm
all t
o in
put e
noug
h fo
rce
to e
xcite
the
hous
ing
above
the
bac
kgro
und
vibr
atio
n.
An
inst
rum
ente
d sl
edge
ham
mer
was
req
uire
d to
inpu
t the
150
0 to
200
0 lb f
nece
ssar
y to
exc
ite th
e ho
usin
g.
CO
NC
LUS
ION
S:
11B
-20
5. T
he m
odal
tes
t dat
a w
ere
curv
e fit
to d
eter
min
e the
mod
e sh
apes
of t
he h
ousi
ng
natu
ral f
requ
enci
es.
Afte
r re
view
ing
the
mod
e sh
apes,
it w
as d
ecid
ed t
o at
tach
a
tem
pora
ry s
tiffe
ner
of 4
x 4
inch
ang
le to
the
vertic
al f
lang
es o
f the
hou
sing
usi
ng
heav
y du
ty C
cla
mps
. V
ibra
tion
data
tak
en w
ith th
e ang
le s
tiffe
ner
clam
ped
to
the
hous
ing
show
ed th
at v
ibra
tion
of th
e 12
77 C
PM
reson
ant
resp
onse
wou
ld b
e lo
wer
ed s
igni
fican
tly if
stif
feni
ng a
t the
pro
per
loca
tions
was
add
ed.
6. R
ecom
men
datio
ns w
ere
mad
e to
bol
t and
wel
d st
ruc
tura
l mem
bers
to
the
fan
hous
ing
base
d on
rev
iew
of t
he m
ode
shap
es (
see
Fig
ure
23).
7. A
fter
the
stiff
ener
s w
ere
inst
alle
d, th
e vi
brat
ion l
evel
s w
ere
redu
ced
from
abo
ut
1.6
in/s
ec to
0.1
5 in
/sec
, (91
% r
educ
tion)
.T
he fa
n hous
ing
1stm
ode
shift
ed f
rom
ab
out
1277
CP
M to
146
2 C
PM
pro
vidi
ng a
sep
arat
ion
marg
in o
f 22.
5% fr
om
runn
ing
spee
d (se
e F
igur
es 2
4 an
d 25
).
8. T
his
proj
ect
took
app
roxi
mat
ely
thre
e ye
ars
from
initi
al in
spec
tion
of th
e fa
ns,
reco
mm
enda
tion
to p
erfo
rm m
odal
tes
ting,
con
duct
ing t
he m
odal
tes
t, in
stal
ling
the
hous
ing
stiff
ener
s an
d re
chec
king
vib
ratio
n.
CO
NC
LUS
ION
S:
11B
-20
©C
opyr
ight
200
5: T
ech
nica
l Ass
ocia
tes
of C
harl
otte
P.C
.
Tha
nks
to M
itche
ll F
ranc
e of
Tec
hnic
al A
ssoc
iate
s of C
harlo
tte, P
C fo
r as
sist
ance
with
the
mod
al te
st, d
ata
redu
ctio
n an
d form
ulat
ing
a so
lutio
n.
Ack
now
ledg
emen
t:
11B
-20
