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By
Mo
ha
mm
ed
S S
ale
em
Sa
ud
i E
lect
rici
ty C
om
pa
ny /
EO
A
Ge
ne
rati
on
Te
chn
ica
l su
pp
ort
De
p.
Co
nte
nts
�
Intr
od
uct
ion
�W
hat
is
Sca
le E
xfo
liat
ion
�S
cale
Gen
erat
ion
�S
cale
Exf
oli
atio
n M
ech
anis
m
�S
cale
Acc
um
ula
tio
n
�S
cale
Acc
um
ula
tio
n m
on
ito
rin
g
�S
cale
exf
oli
atio
ns
Dam
ages
�M
easu
res
to b
e ta
ken
wh
en s
cale
exf
oli
atio
n
Occ
ur
�Q
PP
Exf
oli
atio
n P
rob
lem
s
�C
on
clu
sio
n
Intr
od
uct
ion
�
QP
P h
ad e
xper
ien
ced
tu
be
fail
ure
s in
th
e 2r
ySH
, 3r
ySH
an
d
2ryR
H a
nd
ou
tlet
leg
th
at i
s at
trib
ute
d t
o t
ub
e ex
tern
al
exfo
liat
ion
.
� �T
he
ori
gin
of
the
pro
ble
m i
n b
oth
3ry
SH
an
d 2
ryR
H i
s d
ue
to
hig
her
th
an e
xpec
ted
tu
be
met
al t
emp
erat
ure
. T
he
2ryS
H
pro
ble
m i
s at
trib
ute
d t
o u
nco
ntr
oll
ed d
esu
per
hea
ter
spra
y d
uri
ng
sta
rt-u
p.
�U
nd
er c
erta
in c
on
dit
ion
s, o
xid
e sc
ale
that
fo
rms
on
th
e o
ut
sid
ean
d i
nsi
de
surf
aces
of
sup
erh
eate
rtu
bes
an
d p
ipes
may
bre
ak
loo
se a
nd
exf
oli
ates
. I
t al
so s
usp
ecte
d t
hat
an
exc
essi
ve i
nte
rnal
o
xid
e sc
ale
exfo
liat
ion
wh
ich
cau
se c
om
ple
te o
r p
arti
al p
lugg
ing
of
the
stea
m f
low
pat
h.
�
Wh
at
is S
cale
Exf
oli
ati
on
�H
igh
tem
per
atu
re s
team
rea
cts
wit
h i
nte
rnal
met
al
surf
aces
to
fo
rm a
har
d t
enac
iou
s sc
ale.
�sc
ale
gro
wth
rat
e is
a f
un
ctio
n o
f m
ater
ial
of
con
stru
ctio
n,
tem
per
atu
re,
un
it s
tart
-up
an
d s
hu
tdo
wn
cyc
les.
�B
ecau
se o
f th
e d
iffe
ren
ce o
f co
effi
cien
ts o
f th
erm
al
exp
ansi
on
, ex
pan
sio
n a
nd
co
ntr
acti
on
du
rin
g s
tart
-up
s lo
ose
ns
the
scal
e ca
usi
ng
it
to e
xfo
liat
e (f
lak
es)
�T
he
exfo
liat
ion
pro
cess
is
a m
ech
anic
al p
roce
ss a
nd
du
e o
f so
me
stre
ss e
ffec
t
Sca
le G
en
era
tio
n
�A
fter
sta
rtin
g th
e b
oil
er o
per
atio
n ,
oxi
des
sca
les
gen
erat
es a
nd
sta
rt g
row
ing
�H
2O+
2e-
H2
+O
2-
�F
e++
+ O
2-F
e Y
O
�O
ute
r la
yer
is g
ener
ated
by
the
dif
fusi
on
of
Fe+
+ t
o
stea
m s
ide
(mag
net
ite
(Fe3
O4
) a
nd
hem
atit
e (F
e2O
3)
�In
ner
lay
er i
s ge
ner
ated
by
the
dif
fusi
on
of
O2-
mag
net
ite
, hem
atit
e an
d o
ther
ch
emic
al e
lem
ents
w
hic
h a
re i
ngr
edie
nts
of
ori
gin
al m
ater
ial.
Sca
le E
xfo
lia
tio
n M
ech
an
ism
�T
her
e is
no
str
ess
and
no
cra
ck i
n s
cale
du
rin
g b
oil
er o
per
atio
n.
�B
oil
er s
hu
t-d
ow
n a
nd
sta
rt-u
p ,t
her
mal
str
ess
aris
e at
th
e sc
ale
–met
al b
ou
nd
ary
du
e to
th
e d
iffe
ren
ce o
f th
erm
al e
xpan
sio
n c
oef
fici
ent
bet
wee
n s
cale
an
d m
etal
.
�sc
ale
is t
hin
an
d f
ragi
le t
he
ther
mal
str
ess
mak
es
crac
ks
on
ly i
n t
he
scal
e.
�n
um
ber
/si
ze o
f th
e cr
ack
s an
d o
ther
par
amet
ers
infl
uen
ce o
n t
he
adh
eren
ce f
orc
e o
f sc
ale
�sc
ale
exfo
liat
ion
wil
l ta
ke
pla
ce a
fter
man
y th
ou
san
ds
of
ho
urs
of
serv
ices
Sca
le e
xfo
lia
tio
n p
roce
ss p
ara
me
ters
Sca
le A
ccu
mu
lati
on
�S
cale
acc
um
ula
tio
n s
eem
s ra
nd
om
exc
ept
un
der
th
e co
nd
itio
n t
hat
th
ere
are
som
e te
chn
ical
/d
esig
n r
easo
ns
.
�M
ajo
rity
of
scal
e ac
cum
ula
tio
ns
hap
pen
at
the
bo
un
dar
y o
f in
ner
/ou
ter
laye
rs
�N
ew s
cale
gen
erat
ion
sta
rts
on
fre
sh s
urf
aces
aft
er
nex
t st
art
–up
.
Par
amet
ers
of s
cale
acc
umul
atio
n ar
e su
mm
ariz
ed in
the
fo
llow
ing
tabl
e
Sca
le A
ccu
mu
lati
on
mo
nit
ori
ng
�T
her
e ar
e m
ore
th
an o
ne
way
to
mo
nit
or
the
scal
e ac
cum
ula
tio
n r
eco
mm
end
ed :
•U
ltra
son
ic T
hic
kn
ess
exam
inat
ion
by
EM
AT
S
(Ele
ctro
mag
net
ic A
cou
stic
Tra
nsd
uce
r S
yste
m)
•In
eve
ry o
uta
ge
at l
east
10
% O
f th
e S
H/R
H s
ho
uld
R
T (
X-r
ay)
Insp
ecte
d t
o t
he
tren
d o
f sc
ale
Da
ma
ge
s e
xfo
lia
tio
ns
Sca
le
�20
-30
% o
fsc
ales
are
exf
oli
ated
in
on
e sh
ut
do
wn
an
d s
tart
-up
pro
cess
, p
oss
ibil
ity
of
com
ple
te
plu
ggin
g sh
ou
ld b
e co
nsi
der
ed.
�It
can
cau
se l
on
g te
rm o
verh
eati
ng
and
cre
ep
dam
age
�It
can
cau
se l
on
g te
rm o
verh
eati
ng
�F
ire
sid
e co
rro
sio
n b
ecau
se o
f h
igh
er t
ub
e te
mp
erat
ure
.
�In
cas
e o
fR
H t
his
fla
kin
g p
arti
cles
may
go
th
rou
gh t
o i
nte
rmed
iate
tu
rbin
e an
d d
amag
eth
e b
lad
es
Me
asu
res
to b
e t
ak
en
wh
en
sca
le
exf
oli
ati
on
Occ
ur
�T
he
bo
iler
can
be
sub
ject
ed t
o p
urg
ing
op
erat
ion
to
get
re
d o
f th
e sc
ale
flak
es d
uri
ng
th
e sh
ut-
do
wn
per
iod
.
�If
sca
le a
ccu
mu
lati
on
rat
io o
ver
50%
tu
bes
sho
uld
be
clea
ned
ou
t b
y m
ech
anic
al m
ean
s (B
end
tu
bes
to
be
rem
ove
d t
emp
ora
lly
and
rei
nst
alle
d).
�U
pg
rad
e th
e m
ater
ial
to S
A-2
13 T
P34
7FH
G w
ith
sh
ot
pee
nin
gto
res
ist
inte
rnal
sca
le e
xfo
liat
ion
QP
P E
xfo
lia
tio
n P
rob
lem
s
�Q
PP
Bo
iler
Sp
ecif
icat
ion
�In
199
4,
Qu
rayy
ahP
ow
er P
lan
t U
nit
2 h
ad e
xper
ien
ced
p
rem
atu
re t
ub
e fa
ilu
res
in t
he
3ryS
H a
nd
2ry
RH
o
utl
et l
eg t
hat
is
attr
ibu
ted
to
tu
be
exte
rnal
ex
foli
atio
n
�T
he
ori
gin
of
the
pro
ble
m i
n b
oth
3ry
SH
an
d 2
ryR
H i
s d
ue
to h
igh
er t
han
exp
ecte
d t
ub
e m
etal
tem
per
atu
re
�In
20
02
un
it-4
QP
P h
ad e
xper
ien
ced
tu
be
fail
ure
s in
th
e 2r
ySH
, at
trib
ute
d t
o t
ub
e ex
tern
al e
xfo
liat
ion
.d
esu
per
hea
ter
spra
y d
uri
ng
sta
rt-u
p.
�A
ug
ust
20
07
, fi
rst
tub
e fa
ilu
re w
as e
xper
ien
ced
at
un
it-3
2r
yRH
an
d o
utl
et l
eg t
hat
is
attr
ibu
ted
to
tu
be
exte
rnal
exf
oli
atio
n.
Lap
an
aly
sis
rep
ort
QP
P E
xfo
lia
tio
n P
rob
lem
s
Co
ncl
usi
on
�S
cale
exf
oli
atio
n c
an b
e a
very
ser
iou
s p
rob
lem
if
no
t m
on
ito
red
.
�M
ain
ten
ance
pro
gra
m s
ho
uld
in
clu
de
a sc
hed
ule
fo
r m
on
ito
rin
g t
he
scal
e ac
cum
ula
tio
n i
n t
he
bo
iler
tu
bes
sp
ecia
lly
for
tho
se b
oil
ers
wo
rkin
g c
on
scio
usl
y o
n
hig
h l
oad
.
�C
lose
mo
nit
ori
ng
to
th
e b
oil
er p
erfo
rman
ce m
ay g
ive
a h
igh
in
dic
atio
n o
f sc
ale
accu
mu
lati
on
rat
e.
�A
flu
shin
g p
roce
du
re s
ho
uld
be
ado
pte
d b
y th
e o
per
atio
n i
n o
rder
to
cle
an t
he
tub
es f
rom
th
e ac
cum
ula
ted
sca
le
�T
he
ou
ter
laye
r is
gen
erat
ed b
y th
e d
iffu
sio
n o
f F
e++
to
the
stea
m s
ide
and
in
ner
gen
erat
ed b
y th
e d
iffu
sio
n o
f
O2-
to t
he
met
al S
ide.
�O
ute
r sc
ale
con
sist
s o
f m
agn
etit
e (F
e3O
4)
and
hem
atit
e
(Fe2
O3)
.
�In
ner
sca
le c
on
sist
s o
f m
agn
etit
e (F
e3O
4)
and
hem
atit
e
(Fe2
O3)
an
d o
ther
ch
emic
al e
lem
ents
wh
ich
are
in
gred
ien
ts o
f o
rigi
nal
mat
eria
l.
�S
team
sid
e S
cale
exf
oli
atio
n i
n s
team
pla
nts
is
a ve
ry
seve
r p
rob
lem
wh
ish
can
res
ult
s in
sh
ort
-te
rm
ove
rhea
tin
g b
oil
er t
ub
e fa
ilu
res.
�In
ad
dit
ion
th
e so
lid
par
ticl
es c
an c
ause
th
e so
lid
p
arti
cle
ero
sio
n o
f th
e in
let
stag
es o
f th
e st
eam
tu
rbin
es(
inte
rmed
iate
tu
rbin
e st
ages
)
Acc
um
ula
tio
n R
ate
�In
sca
le w
hic
h h
as g
row
n b
eyo
nd
a c
erta
in t
hic
kn
ess,
th
e o
ute
r la
yer
exfo
liat
es d
ue
to t
he
dif
fere
nce
in
th
erm
al e
xpan
sio
n b
etw
een
th
e tu
be
mat
eria
l an
d t
he
scal
e d
uri
ng
sta
rt a
nd
sto
p o
f th
e b
oil
er
rate
pe
en
ing
Ma
teri
al
Up
gra
de
an
d s
ho
t
QP
P F
ail
ure
QP
P T
ub
e
fail
ur
QP
P F
ail
ure
QP
P 2
YR
h A
nd
3ry
SH
U3
IP
tu
rbin
e b
lad
es
Gh
azl
an
de
po
sits
U3
IP
tu
rbin
e b
lad
es
Gh
azl
an
da
ma
ge
s
