mitigate corrosion in condensate

8/19/2019 Mitigate Corrosion in Condensate

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WHY BAD THINGS HAPPEN

TO GOOD STEAM EQUIPMENTBy Jim Risko, TLV Corp. | March 1, 2015

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Sharin% Ser&ice# 4

Accounting for an entire steam-trap population is crucial to avoiding

safety incidents and sub-optimal production — high-priority

consideration must be given to steam-system management

Hi#torica!!'( #tea #'#te# ha&e "ro&i)e) the o#t e*ecti&e #o+rce of rea)i!'

con&e'ab!e heat to in)+#tria! "roce## a""!ication#( inc!+)in% tho#e in the cheica!

"roce## in)+#trie# ,-PI.( an) there i# no #ii!ar !ow/co#t #+b#tit+te that can

re"!ace #tea0 Witho+t #tea( in)+#tria! "ro)+ction wo+!) be )raatica!!'

c+rtai!e)( an) the !ow/co#t an+fact+re) "ro)+ct# that are a)e fro #tea1#

heat or "ower/%eneration a##i#tance wo+!) not e2i#t0 Witho+t #tea( o+r 3+a!it'

of !ife( econoie# an) #ociet' in %enera! wo+!) #+*er0

Whi!e an' -PI worker# a' a""reciate that #tea #'#te# are a nece##it'( the

#ae in)i&i)+a!# a' ha&e a!#o e2"erience) ne%ati&e #tea/re!ate) inci)ent#

thro+%ho+t their career#( akin% the harbor +nfa&orab!e tho+%ht#0 S"eci4ca!!'(

the#e e&ent# a' ha&e re#+!te) in #afet' i##+e#( e3+i"ent fai!+re# an)

+n#che)+!e) #h+t)own# of a +nit or a f+!! "ro)+ction !ine0 Safet' e&ent# are

e2tree!' cha!!en%in% an) #orrowf+! i##+e# if #oeone i# in5+re)( an) #h+t)own#

can be )i#r+"ti&e to the entire workforce0 It i# not #+r"ri#in%( then( that "eo"!e

!ack an enth+#ia#tic attit+)e when it coe# to #tea0

WHAT -AN GO W6ONG IN A STEAMSYSTEM7

What t'"e# of i##+e# can ari#e in a #tea #'#te( an) can !i#tin% an) c!a##if'in%

the#e ite# he!" to )eterine an e2ec+tab!e "re&ention "ath or ri#k/iti%ation

"roce)+re7 Of co+r#e( it i# re!ati&e!' ea#' to i)entif' the o#t coon a!a)ie#

#een in a #tea #'#te0 There can be waterhaer( ero#ion )aa%e an) #tea

!eak# in +ti!it' #'#te# or e3+i"ent0 S+ch )e#tr+ction a' ren)er critica!

"roce## e3+i"ent( #+ch a# t+rbine#( 8are# or heat e2chan%er#( +n+#ab!e0

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A))itiona!!'( hi%h ret+rn/#'#te back"re##+re ca+#e) b' #tea !eaka%e or

b!owthro+%h fro b'"a## #tea i%ht re#trict "ro)+ction 3+antit' or 3+a!it'

thro+%h heat/e2chan%e e3+i"ent0 Back"re##+re can a!#o ca+#e the heat/

e2chan%e a""!ication to be "+t on b'"a## or to wa#te con)en#ate b' ro+tin% to

%ro+n) !e&e!0 Whi!e #oe #tea/#'#te fai!+re# are coon( the cha!!en%e theni# to i)entif' the #o+rce# of the#e inci)ent#0 Thi# !ea)# to the !ar%er 3+e#tion(

9Wh' )o ba) thin%# ha""en to %oo) #tea e3+i"ent7:

The technica! an#wer !ie# in +n)er#tan)in% that the ca+#e for a !ar%e "ercenta%e

of fai!+re# i%ht be )+e to the #tea #'#te not bein% aintaine) to the 9a#/

b+i!t: or 9)e#i%n: #"eci4cation0 The ori%ina! )e#i%ner# ana!';e) the "!ant

re3+ireent# an) )eterine) the o#t #+itab!e )e#i%n( accor)in% to their

e2"erti#e an) #tan)ar)#0 That ori%ina! )e#i%n inc!+)e) the correct n+ber of

#tea tra"# an) the a##eb!a%e of "i"in% an) co"onent# that he!" to )raincon)en#ate fro the #'#te0 -oon!' referre) to a# a con)en#ate )i#char%e

!ocation ,-D


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Figure 1. !!ec"i#e s"eam "raps keep hea" i$ "he sys"em "o op"imi%e pro&uc"io$ ra"es a$& hea" 'ua(i"y, a$& "hey a(so &ischarge

co$&e$sa"e "o pro#i&e !or sys"em sa!e"y a$& re(ia)i(i"y. Ma*or pro)(ems ca$ occur i! co$&e$sa"e is $o" rea&i(y &rai$e& !rom "he

sys"em

Stea tra"# ,?i%+re @. are +bi3+ito+# in #tea #'#te#( an) when o"eratin%

e*ecti&e!'( the' can ecient!' retain heat in the #'#te0 -on#i)er the ana!'#i# of

a h'"othetica! "!ant1# #tea/tra" "o"+!ation #hown in ?i%+re 0 Ba#e) on thi#

"!ant1# 9#tate of the "o"+!ation: #+ar'( it i# #een that the ori%ina! )e#i%n ,an)

a#/b+i!t. con)ition inc!+)e) @@(CCC -D


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-on#i)er that the a&era%e ann+a! fai!+re rate of a #tea tra" "o"+!ation in a

at+re "!ant can be e#tiate) fro hi#torica! recor)#( "ro&i)e) that there are at

!ea#t two #+r&e' e&ent# within a "erio) of KLJ 'ear#0 Si"!' #+btract the

carr'o&er fai!+re# ,fai!e) tra"# recor)e) fro a "rior #+r&e' for which no actionwa# taken to re"air. fro the re"orte) fai!+re# that were recor)e) in the #+r&e'0

The reain)er i# the 3+antit' of new fai!+re#0 The n+ber of new fai!+re# can be

)i&i)e) b' the n+ber of 'ear# #ince the "rior #+r&e' to "ro&i)e an e#tiate of

the a&era%e ann+a! new fai!+re# of a #tea tra" "o"+!ation0 Se&era! re!ate) +#ef+!

ca!c+!ation# are #hown in the ca!c+!ation bo2 be!ow0

In thi# h'"othetica! "!ant hi#tor'( if the ana%eent of the tra" "o"+!ation ha)

been contin+o+# an) #+#tainab!e at

an ann+a! fai!+re rate of @(CCC ,@C.( then the "!ant #ho+!) on!' ha&e to #+""ort

the re"air of K tra"# "er onth( not JC tra"#0 Howe&er( in thi# ca#e( the tra"

"o"+!ation wa# a!!owe) to )eteriorate to (CCC fai!+re# ,C fai!+re #tate.( an)

thi# #it+ation "!ace# a treen)o+# b+r)en on re#o+rce#0 Wor#e #ti!!( if not

correcte)( the fai!+re# can be e2"ecte) to %row +nti! cata#tro"hic e&ent# occ+r0

One takeawa' fro thi# e2a"!e i# that for e&er' @(CCC tra"# that +#t be

re"aire) in a 'ear( there i# a re3+ireent for the "!annin% an) re"air re#o+rce# to

correct K tra"# onth!' witho+t fai!0 That re"!aceent re3+ireent e3+ate# to

re"airin% KLJ -D


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co!) fai!+re = then the -D< i# no !on%er #er&in% it# inten)e) "+r"o#e( an) +#t be

re"aire)0

I# there an' 3+e#tion abo+t what o+tcoe #ho+!) be e2"ecte) if a!! of the #tea

tra"# an) re!ate) -D


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Figure . +ccura"e a$& regu(ar(y sus"ai$e& &iag$osis o! s"eam "raps6 opera"i$g co$&i"io$s is esse$"ia( "o &e"ermi$i$g "he

popu(a"io$6s curre$" hea("h -s"a"e o! "he popu(a"io$/. 7$ce !ai(ures are i&e$"i!ie&, "he i$!orma"io$ is #a(ua)(e !or a((oca"i$g

resources "o res"ore a(( co$&e$sa"e &ischarge (oca"io$s "o a$ as &esig$e& opera"i$g co$&i"io$ !or sa!e"y a$& re(ia)(e

per!orma$ce

In a "ro"er!' )raine) an) aintaine) #tea #'#te( it i# critica! that the #tea

8owin% within the #'#te reain# at near/#at+rate) 3+a!it' an) that a&oi)ab!e

back"re##+re in the ret+rn hea)er i# re)+ce)( in or)er to )iini#h the !ike!ihoo) of

waterhaer( ero#ion( corro#ion an) "!atin%0 S+"erheate) #tea or #tea with

near/#at+ration 3+a!it' nora!!' cannot ca+#e haer or hi%h ero#ion at nora!

&e!ocitie# beca+#e there i# not eno+%h con)en#ate to be "ro"e!!e) )own#trea0Haer an) ero#ion occ+r when !i3+i) "oo!# in the #'#te are thr+#t at hi%h

#"ee)#( b+t when a #'#te i# "ro"er!' )raine)( the )aa%in% co"onent i#

i##in%0 Once a%ain( it i# e&i)ent that #tea/tra" fai!+re rate# are re)+ce) in

#+cce##f+!!' aintaine) #tea #'#te#( enab!in% ecient con)en#ate reo&a!

fro the #'#te0

Maintainin% -D


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EA


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Figure 8. 7!"e$, high priori"y is gi#e$ "o !i4i$g "he (eakage !ai(ures or ho" !ai(ures "o re&uce s"eam (oss a$& i$crease pro!i".

Commo$(y, "he repair o! ho" !ai(ures 3i"h high#a(ue (oss is gi#e$ !irs" priori"y i$ i$s"a$ces o"her "ha$ #ery cri"ica( app(ica"io$s.

+ represe$"a"i#e e4amp(e o! "he corre(a"io$ o! year(y repairs "o re&uc"io$ i$ s"eam (oss is sho3$ here


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Figure 5. For %ero rese" o! a(( ,000 !ai(ures, mo$"h(y rep(aceme$" o! 250 CLs is re'uire&. ! ac"ua( rep(acem$e$"s mo$"h(y are

re&uce&, "he gap resu("s i$ yeare$& carryo#er !ai(ures "ha" re&uce "he e!!ec"i#e goo& i$ser#ice CLs i$ "he $e4" year

The carr'o&er fai!+re# re"re#ent the rea! wor!) rare!' )o "!ant# correct a!! or e&en

near!' a!! of the fai!+re#0 The re#+!t i# that a #i%ni4cant n+ber of -D


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are con#tant!' occ+rrin%( a# i!!+#trate) in ?i%+re 0

Figure 9. There is a(3ays a$ i&e$"i!ica"io$repair respo$se"ime (ag )e"3ee$ &iag$osis a$& mai$"e$a$ce ac"io$. +("hough a si"e

may e(ec" "o per!orm su!!icie$" repairs "o reach a "arge" s"a"e o! "he CL popu(a"io$ a" yeare$&, $e3 !ai(ures occuri$g &uri$g "he

repair perio& a(3ays (o3er "he ac"ua( yeare$& s"a"e. " is *us" o$e o! ma$y *us"i!ica"io$s !or a&op"i$g a %ero rese" me$"a(i"y !or

mai$"e$a$cerespo$se p(a$$i$g

If carr'o&er fai!+re# are inc!+)e) a# "art of the re"air #trate%'( a #i%ni4cant

n+ber of -D


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#it+ation( the carr'o&er fai!+re# i%ht be con#i)ere) acce"tab!e +n)er the

circ+#tance#( an) a new %oa! i# a##i%ne) for the ne2t 'ear0 Howe&er( thi# i# a

)an%ero+# #it+ation( beca+#e whi!e the "otentia! for )aa%e i# not &i#ib!e( it i#

"re&a!ent in the +na))re##e) #ection# of the #tea #'#te( an) the )own#trea

reci"ient# of that #tea0 The "otentia! for "eri! can increa#e in #e&erit' o&er tie0

Witho+t a f+!! +n)er#tan)in% of the !on%ter i"act on a #tea #'#te( there can

e2i#t a fa!#e i"re##ion that a #'#te can be we!! ana%e)( e&en if there i#

a!!owance for carr'o&er fai!+re#0 ?i%+re F "ro&i)e# a))itiona! in#i%ht into a !on%er/

ter &iew0 A# it t+rn# o+t( the be#t "o##ib!e theoretica! #tate of the "o"+!ation

occ+r# on!' after a ;ero re#et con)ition i# e2"erience) fro the "rior #+r&e'

re"ort( an) when acc++!ate) re"air# e3+a! new acc++!ate) fai!+re#0 After the

i)wa' "oint( ;ero re#et ha# been theoretica!!' reache)( an) new re"!aceent#

cea#e( a# there are no known fai!+re# that reain to be re"aire)0 Howe&er(+ni)enti4e) new fai!+re# are #ti!! occ+rrin% an) wi!! not be reco%ni;e) +nti! the

ne2t #+r&e'0

Figure :. ;i"es some"imes &eci&e upo$ a !i4e& $um)er o! a$$ua( repairs i$s"ea& o! s"ri#i$g !or %ero rese", "hi$ki$g "hey ca$

achie#e a $ear(y 100< goo& i$ser#ice CL popu(a"io$ s"a"e o#er se#era( years. =o3e#er, &ue "o $e3 !ai(ures &uri$g "he repair

cyc(e, "he "heore"ica( )es" sus"ai$a)(e co$&i"io$ is reache& mi&3ay "hrough a per!ec"(y corre(a"e&, (i$ear i$spec"io$ a$& repair

"erm, a!"er 3hich "he $um)er o! CLs i$ goo& co$&i"io$ 3i(( &ec(i$e


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The re#+!t i# that the be#t #tate )eteriorate# between the "rior an) new #+r&e'#(

with the theoretica! 9be#t #+#tainab!e: con)ition bein% rea!i;e) at the be%innin%

)ate of the ne2t #+r&e'0 Thi# theoretica! "oint occ+r# i)wa' between the "rior#+r&e' an) the ne2t #+r&e' )ate = if ann+a! #+r&e'# are con)+cte)( an) re"air i#

ie)iate an) !inear( then the be#t %oo) #tate occ+r# at i)'ear0

If the ori%ina! %oa! of the )e#i%ner# i# reca!!e)( it wa# to ha&e @@(CCC f+!!'

f+nctiona! -D


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o"eratin% "!ant0 It #ho+!) not be a #econ)/ or thir)/"riorit' foc+#( b+t the ke'

foc+#( th+# he!"in% to en#+re an o"tii;e) #tea #'#te0

Another i"ortant factor that +#t be a))re##e) i# o+t#o+rcin%( which i# the

a!!ocation of re#"on#ibi!itie# to thir)/"art' entitie# a# contractor# to "erforcertain work0 In or)er to achie&e a #+#tainab!e "ro%ra +n)er an o+t#o+rcin%

#cenario( there are #e&era! cr+cia! re3+ireent# certi4e) te#t "er#onne!

&a!i)ate) e3+i"ent for akin% acc+rate con)ition 5+)%ent# an) #tan)ar)i;e)

a""!ication )rawin%# for correct in#ta!!ation of re"aire) e3+i"ent0 In #oe "!ant#(

te#tin% an) aintenance a' be con)+cte) b' the #ae thir)/"art' entit'0

6e%ar)!e##( whether a #in%+!ar thir)/"art' or +!ti"!e entitie# are in&o!&e) with

acti&itie# that can a*ect the #tate of the "o"+!ation( it i# i"ortant that the

ca"abi!it' for each "roce## i# con4re)0 ?or e2a"!e( an incre)ib!' ca"ab!e

contractor for "i"in% re"air a' be in#+cient!' traine) for te#tin% acti&itie#( an)+#t be #+itab!' e)+cate) an) certi4e) for the#e ta#k#0 Mo#t critica!!'( there

#ho+!) e2i#t a re%+!ar a+)it "roce## to check an) con4r the acc+rac' of the

#+r&e'or#1 3+a!i4cation certi4cate#( the act+a! 5+)%ent# "erfore) b' tho#e

#+r&e'or#( an) in the ca#e of aintenance contractor#( the correct in#ta!!ation of

each re"aire) -D


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Figure >. The $um)er o! i$ser#ice CLs is a(rea&y a re&uc"io$ !rom "he $um)er o! CLs i$ "he origi$a( &esig$, 3hich is $o"

&esira)(e u$(ess c(ear(y *us"i!ie&? a$& e#e$ 3i"h a %ero rese" !ocus a$& per!ec"(y harmo$i%e& i$spec"io$ a$& repair, "he )es"

sus"ai$a)(e co$&i"io$ is co$"ro((e& )y "he $um)er o! a$$ua( !ai(ures. s"a)(ishi$g cri"ica( "hresho(& #a(ues pro#i&es c(ear

&irec"io$ !or sus"ai$a)(e s"eamsys"em per!orma$ce

If a "!ant want# to ha&e a #econ)ar' foc+# on co!) fai!+re# to re)+ce "rob!e#

ca+#e) b' con)en#ate in the #'#te( or to re"air hot fai!+re# to re)+ce

back"re##+re an) reco&er "ro4t# !o#t to +nnece##ar' ener%' "ro)+ction( that i#

certain!' a 4ne a""roach to 42in% fai!e) -D


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Figure @. + para&igm shi!" &irec"s !u(( a""e$"io$ "o "he per!orma$ce)ase& me"ho&, ra"her "ha$ !ocusi$g mai$(y o$ ho" !ai(ures.

A$o3i$g "he $um)er o! goo& CLs re(a"i#e "o key "hresho(& (e#e(s pro#i&es a c(ear i$&ica"io$ o! "he s"eam sys"em6s hea("h

a$& per!orma$ce e4pec"a"io$s

When the %oa! i# to aintain a #tate of the "o"+!ation at or abo&e 9ini+

%oo): !e&e!# for #afet' an) re!iabi!it' con#i)eration#( the tar%et i# #trai%htforwar)0

Now( the re"air of fai!+re# becoe# 5+#t a "ath( not a %oa!0 With a c!ear e##a%e

to "er#onne!( the #tea/#'#te )raina%e can be o"tii;e) an) #+#taine) for be#t

"!ant "erforance0■

Edited by Mary Page Bailey

AUTHO6

ae# 60 6i#ko i# the "re#i)ent of T


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-ontro!# In#tit+te ,?-I.( an) ha# "re&io+#!' #er&e) a# the or%ani;ation1# chairan(

#tan)ar)# chair( an) chair of the Secon)ar' Pre##+re an) Stea Tra" #ection#0 He

ha# earne) three ener%'/ana%eent certi4cation#( fro the A##ociation of

Ener%' En%ineer#( North -aro!ina State Uni&0( an) the In#tit+te of Ener%'

Profe##iona!#0 He ho!)# an M0B0A fro Wi!ke# Uni&er#it'( an) two B0S0 )e%ree#( inatheatic#e)+cation an) b+#ine## a)ini#trationacco+ntin%( fro +t;town

Uni&er#it'0 He i# a!#o !icen#e) a# a -erti4e) Ener%' Mana%er ,-EM. an) a

Profe##iona! Ener%' Mana%er ,PEM.0

WEB/ON


17/27

"henoenon/"t@0ht!( T


18/27

sys"em. This ar"ic(e pro#i&es a$ o#er#ie3 o! some curre$" "ech$o(ogies use& "o com)a" "he u$&er(yi$g

corrosio$ issues i$ co$&e$sa"ere"ur$ sys"ems, a$& "he 3ays "o &ep(oy "hese corrosio$mi"iga"io$

"ech$i'ues e!!ec"i#e(y.

CORROSION MECHANISMS

+s a !irs" s"ep "o com)a" co$&e$sa"esys"em corrosio$, "he i$gress o! gases i$"o "he co$&e$sa"e sys"em

shou(& )e mi$imi%e&. $gress o! gases ca$ occur i$ "he !o((o3i$g 3aysD

• Eo$co$&e$sa)(e gases -C72 or 72/ a)sor)e& !rom "he air ca$ &isso(#e i$ )oi(er makeup 3a"er?

i$ "his case, "he $o$co$&e$sa)(e gas !(ashes o#er "he s"eam a$& e#e$"ua((y !i$&s i"s 3ay i$"o

"he co$&e$sa"e

• +)sorp"io$ o! $o$co$&e$sa)(e gases i$ e'uipme$" "ha" is i$i"ia((y !u(( o! air -s"eami$g

opera"io$ &uri$g s"ar"up/ or air (eakage i$ e'uipme$" "ha" is ha$&(i$g s"eam a" su)

a"mospheric pressures


19/27

• C72 pro&uce& i$ "he )oi(er )y "he &ecomposi"io$ o! )oi(er!ee&3a"er a(ka(i$i"y "ha" has

&isso(#e& i$"o "he co$&e$sa"e

The !o((o3i$g sec"io$ ou"(i$es some speci!ic chemica(reac"io$ mecha$isms "ha" ca$ cause corrosio$ i$

s"eamco$&e$sa"e re"ur$ sys"ems.

Condensate system corrosion in the presence of oxygen.The !o((o3i$g reac"io$ represe$"s "he

corrosio$ o! iro$ -Fe/ i$ 3a"er 1 GD

Fe H 2=27 V Fe-7=/2 H =2

This reac"io$ co$"i$ues "o e'ui(i)rium i! $o 7 2 is prese$" 2 G. +(so, "he !orma"io$ o! !errous hy&ro4i&e

-Fe-7=/2/ i$creases "he co$&e$sa"e p= a$& re"ar&s "he reac"io$ ra"e. Ihe$ 72is prese$" i$ "he

co$&e$sa"e, "he !o((o3i$g reac"io$ occurs, !ormi$g hy&ra"e& !erric o4i&e-Fe27 .=27/D

8Fe-7=/2 H 72 V 2Fe27 .=27 H 2=27

Ferric o4i&e, a(so ca((e& hema"i"e or re& rus", is a (oose(y a&heri$g o4i&e (ayer, a$& ca$ "ra#e( 3i"h "he

co$&e$sa"e !(o3 "hrough "he co$&e$sa"e pipi$g. +$ e4amp(e o! iro$o4i&e corrosio$ is sho3$ i$ Figure

1.


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Figure 1. $ "he prese$ce o! o4yge$, !errico4i&e corrosio$ occurs, a$& ca$ 3reak ha#oc o$ co$&e$sa"e sys"em e'uipme$"

The i$gress o! &isso(#e& 72 i$ "he co$&e$sa"e pre#e$"s e'ui(i)rium !rom )ei$g reache&, a$& !errous

hy&ro4i&e is remo#e& co$"i$uous(y !rom "he i$$er 3a((s o! "he pipi$g a$& !i""i$gs 2 G. The !o((o3i$g

are "he "3o "ypes o! corrosio$ "ha" occur 3he$ 72is prese$" 3 GD

• e$era(i%e& corrosio$ o$ "he me"a( sur!ace, 3hich causes a (oss o! me"a( !rom "he e$"ire

sur!ace

• 74yge$ pi""i$g, 3hich causes a high(y (oca(i%e& (oss o! me"a( "ha" ca$ resu(" i$ a ca"as"rophic

!ai(ure i$ a shor" "ime. i""i$g )egi$s a" 3eak poi$"s i$ "he o4i&e !i(m a$& a" (oca"io$s 3here

"he !i(m is &amage&. The corrosio$ pe$e"ra"es i$"o "he sur!ace, e!!ec"i#e(y &ri((i$g a ho(e i$"o

"he me"a(


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Condensate system corrosion in the presence of CO 2 . Car)o$a"es a$& )icar)o$a"es, such as so&ium

)icar)o$a"e -Ea=C7/ or so&ium car)o$a"e -Ea2C7/, are commo$(y prese$" i$ )oi(er makeup 3a"er,

a$& "hese a$io$s are ge$era((y ca((e& 3a"er a(ka(i$i"y. Ii"h "he app(ica"io$ o! hea", "hese car)o$a"esu$&ergo "he !o((o3i$g reac"io$s i$ "he )oi(er 1, 3 GD

2Ea=C7 H hea" V Ea2C7 H C72 H =27

Ea2C7 H =27 H hea" V 2Ea7= H C72

+s "he s"eam !rom "he )oi(er "ra$s!ers i"s (a"e$" hea" a$& co$&e$ses, "he C72&isso(#es i$ "he co$&e$sa"e,

&epressi$g "he p=.

The !o((o3i$g re#ersi)(e reac"io$s "ake p(aceD

=27 H C72 V =2C7

=2C7 V =H H =C7 K

=C7 K V =H H C7 2K

The corrosio$ o! iro$ )y car)o$ic aci& -=2C7/ is promo"e& )y hy&roge$ io$s -=H/ !rom "he a)o#e

&issocia"io$ reac"io$s. The o#era(( reac"io$ !ormi$g !errous )icar)o$a"e -Fe-=C7/2/ isD

2=H H 2=C7 K H Fe V Fe-=C7/2 H =2

+ (o3 p= causes ge$era(i%e& (oss o! me"a(, ra"her "ha$ "he (oca(i%e& pi""i$g cause& )y 7 2. Corrosio$ is

charac"eri%e& )y "he ge$era( "hi$$i$g o! "he pipe 3a(( or groo#i$g a(o$g "he )o""om o! "he pipe 2 G.

This "hi$$i$g o!"e$ (ea&s "o !ai(ures, par"icu(ar(y a" "hrea&e& *oi$"s. $ a&&i"io$, corrosio$ "ha" causes

&ecay o! pipe 3a((s (ea&s "o &e)ris "ha" ca$ &eposi" i$ sma(( par"s, causi$g )(ockage, as see$ i$ Figure

2.


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Figure 2. Corrosio$ i$ pipe 3a((s ca$ (ea& "o 3i&esprea& issues, i$c(u&i$g "he !orma"io$ o! &eposi"s a$& )(ockages i$ sma((

pipi$g compo$e$"s

COMBATTING CORROSION

+s s"a"e& pre#ious(y, "he i$gress o! 72 or C72 i$"o "he co$&e$sa"e is "he mai$ cause o! corrosio$ i$

co$&e$sa"e sys"ems. =e$ce, a$y e!!or" "o re&uce corrosio$ "o accep"a)(e (e#e(s mus" &ea( 3i"h e4pe((i$g

"hese gases !rom )oi(er 3a"er a$& $eu"ra(i%i$g "heir corrosi#e e!!ec" 3i"h "he a&&i"io$ o! chemica(s

1, 3 G. The mai$ processes !or !igh"i$g co$&e$sa"esys"em corrosio$ are summari%e& i$ "he !o((o3i$g

sec"io$s.

Deaeration. The )oi(er !ee&3a"er is mai$(y comprise& o! makeup 3a"er a$& re"ur$ co$&e$sa"e.

isso(#e& 72 is primari(y prese$" i$ )oi(er makeup 3a"er, 3hi(e &isso(#e& C72ca$ )e prese$" i$ "here"ur$ co$&e$sa"e. Bo"h gases i$"ro&uce corrosio$ po"e$"ia( !or "he )oi(er a$& "he co$&e$sa"e sys"em.


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eaera"io$ e!!ec"i#e(y re&uces &isso(#e& $o$co$&e$sa)(e gases !rom !ee&3a"er. $ "he &eaera"io$

process, "he makeup 3a"er a$& re"ur$ co$&e$sa"e are hea"e& i$ a &eaera"or #esse( 3i"h (o3pressure

s"eam "o a "empera"ure "ha" is su!!icie$" "o re&uce "he par"ia( pressure o! "he &isso(#e& gases o#er "he

3a"er sur!ace. This resu("s i$ a(mos" a(( o! "he &isso(#e& gases comi$g ou" o! "he (i'ui& phase. The

&isso(#e& gases are #e$"e& !rom "he &eaera"or #esse( a(o$g 3i"h a sma(( amou$" o! (o3pressure s"eam"o ai& #e$"i$g. This process is k$o3$ as mecha$ica( &eaera"io$.

Chemical oxygen scavenging. ;ome resi&ua( 72 remai$s a!"er mecha$ica( &eaera"io$, as "he par"ia(

pressure o! 72 ca$$o" )e re&uce& "o %ero. This is a po"e$"ia( source !or 72corrosio$. Chemica(s are

a&&e& "o reac" 3i"h "he (e!"o#er 72. The chemica( is usua((y a&&e& )e(o3 "he 3a"er (e#e( i$ "he 3a"er

s"orage sec"io$ o! "he &eaera"or. The mos" commo$ 72sca#e$ger is ca"a(y%e& so&ium su(!i"e -2Ea;7/,

3hich has "he !o((o3i$g reac"io$D

2Ea;7

H 72

2Ea;78

+$o"her 72 sca#e$ger is &ie"hy(hy&ro4y(ami$e -=+? 8-C2=5/2 E7=/. The o#era(( reac"io$ o! 72 3i"h

=+ is as !o((o3sD

8-C2=5/2 E7= H @72 V >C=C77= H 2E2 H 9=27

The a&&i"io$ o! =+ a(so has a passi#a"i$g ac"io$ o$ me"a( sur!aces. Ihe$ hy&ro4i&e a(ka(i$i"y is

prese$" i$ "he )oi(er 3a"er, "he ace"ic aci& is $eu"ra(i%e& a$& remo#e& i$ )(o3&o3$ as so&ium ace"a"e.

CONTROLLING CORROSION

The o)*ec"i#e o! chemica( co$"ro( i$ "he co$&e$sa"e is "o e(e#a"e "he co$&e$sa"e6s p= so "ha" "he i$gress

o! car)o$ic aci& is $eu"ra(i%e&. Eeu"ra(i%i$g ami$es -RKE=2/ are use& "o $eu"ra(i%e "he aci&ic =H "ha" is

ge$era"e& )y "he &issocia"io$ o! car)o$ic aci&. Eeu"ra(i%i$g ami$es a(so ser#e "o i$crease "he p= o! "he

co$&e$sa"e. The ami$es hy&ro(y%e 3he$ a&&e& "o 3a"er, a$& ge$era"e "he hy&ro4i&e io$s "ha" are

$ecessary !or $eu"ra(i%a"io$. The chemica( reac"io$ !or a $eu"ra(i%i$g ami$e i$ 3a"er is as !o((o3sD

RKE=2 H =27 V RKE= H H 7= K

The o#era(( $eu"ra(i%a"io$ reac"io$ is sho3$ )e(o3D

RKE= K H 7= K H =2C7 V RKE= H H =C7 K H =27

By regu(a"i$g "he &osi$g ra"e o! "he $eu"ra(i%i$g ami$e, "he p= o! "he co$&e$sa"e ca$ )e e(e#a"e& "o "he

&esire& (e#e(. Ma$y ami$es are use& !or co$&e$sa"eaci& $eu"ra(i%a"io$ a$& p= e(e#a"io$. Morpho(i$e

a$& cyc(ohe4y(ami$e are commo$ $eu"ra(i%i$g ami$es. 7!"e$, a )(e$& o! morpho(i$e a$&

cyc(ohe4y(ami$e is a )e""er choice "ha$ usi$g ei"her a(o$e. The choice o! $eu"ra(i%i$g ami$e &epe$&s


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upo$ "he &is"ri)u"io$ ra"io a$& "he $um)er o! co$&e$sa"io$ si"es 3 G.

+$o"her op"io$ !or co$"ro((i$g co$&e$sa"esys"em corrosio$ is "he use o! !i(mi$g ami$es.

7c"a&ecy(ami$e is a commo$ !i(mi$g ami$e. Fi(mi$g ami$es are i$"ro&uce& i$"o "he s"eam hea&er, a$&

!orm a #ery "hi$ ami$e!i(m )arrier o$ "he me"a( sur!ace )y rep(aci$g "he (oose o4i&e sca(e. This )arrier (ayer pre#e$"s 72 a$& car)o$ic aci& !rom reachi$g "he )ase me"a( i$ "he co$&e$sa"ere"ur$ (i$es. uri$g

"he i$i"ia( &osi$g perio&, (oose(y a&here& o4i&e &eposi"s are (i!"e& o!! o! "he me"a( sur!ace a$& rep(ace&

)y a$ ami$e !i(m. This is &ue "o "he sur!ac"a$" proper"ies o! "he ami$e.

$ "he case o! o(& or u$"rea"e& co$&e$sa"e (i$es, e4cessi#e &osage o! !i(mi$g ami$es ca$ &is(o&ge pre

e4is"i$g &eposi"s a$& "he s(u&ge ca$ !ou( "he co$&e$sa"ere"ur$ sys"em. This s(u&ge ca$ po"e$"ia((y

reach "he )oi(er, causi$g "u)e !ai(ures. =o3e#er, !or u$i!orm a$& e!!ec"i#e co#erage o! a (arge

co$&e$sa"ere"ur$ sys"em, a )(e$& o! a s"raigh" !i(mi$g ami$e 3i"h a $eu"ra(i%i$g ami$e a$& emu(si!iers

pro#i&es a superior !i(m )o$&, re&uces &eposi" pro)(ems a$& pro#i&es )e""er a$& more eco$omica(sys"em co#erage 3 G.

e" a$o"her op"io$ !or a)a"i$g corrosio$ i$ co$&e$sa"e sys"ems is "he use o! =+ as a me"a(

passi#a"or a$& 72 sca#e$ger. =+ co$#er"s (oose, u$pro"ec"i#e iro$ o4i&e -re& hema"i"e/ &eposi"s o$

"he co$&e$sa"e pipe6s i$$er sur!aces "o a )(ack mag$e"i"e pro"ec"i#e !i(m, !errous o4i&e mag$e"i"e

-Fe78/. The !o((o3i$g is "he chemica( reac"io$ !or "his co$#ersio$ 1 GD

8-C2=5/2E7= H 9Fe27 V 8Fe78 H 8C=C77= H =27

The mag$e"i"e (ayer o$ "he me"a( sur!aces re&uces corrosio$ ra"es !rom 72 a$& car)o$ic aci&. =+ is

usua((y &ose& a(o$g 3i"h a $eu"ra(i%i$g ami$e, as i" is mos" e!!ec"i#e a" a p= higher "ha$ >. =+ has

a high &is"ri)u"io$ ra"io &ue "o i"s high #o(a"i(i"y, a$& he$ce pro#i&es e!!ec"i#e pro"ec"io$ )y &irec"(y

&osi$g i" i$"o "he )oi(er !ee&3a"er i$s"ea& o! i$"o "he s"eam hea&er. ue "o "he high &is"ri)u"io$ ra"io,

=+ a(so sprea&s more e!!ec"i#e(y "o "he e$"ire s"eam a$& co$&e$sa"e sys"em 1 G.

Boi(er makeup 3a"er "ha" is (o3 i$ a(ka(i$i"y he(ps i$ re&uci$g car)o$ic aci& corrosio$ i$ co$&e$sa"e

sys"ems. +(so, (ess ami$e a&&i"io$ is re'uire&. ea(ka(i%ers a$& re#erse osmosis ca$ )e co$si&ere& !or

"he "rea"me$" o! )oi(er makeup 3a"er "o re&uce a(ka(i$i"y.

Ihe$ co$&e$sa"e i$ "he pipi$g is $ear i"s sa"ura"io$ "empera"ure, car)o$ic aci& !orma"io$ is mi$imi%e&,

as "he so(u)i(i"y o! C72 i$ "he co$&e$sa"e is (o3. =o3e#er, i! "he "empera"ure o! "he co$&e$sa"e is

)e(o3 "he sa"ura"io$ "empera"ure, (ike(y &ue "o improper i$su(a"io$ o! "he co$&e$sa"e (i$es, more

C72 goes i$"o so(u"io$, causi$g po"e$"ia( car)o$icaci& corrosio$. There!ore, i" is impor"a$" "ha"

co$&e$sa"e re"ur$ (i$es are proper(y i$su(a"e& a$& "ha" "he i$"egri"y o! "he i$su(a"io$ is mai$"ai$e&

&uri$g "he (i!espa$ o! "he s"eam co$&e$sa"e sys"em.

MONITORING CORROSION


25/27

Mo$i"ori$g corrosio$ i$ co$&e$sa"ere"ur$ sys"ems a((o3s !or ear(y &e"ec"io$ o! pro)(ems 3he$ "he

pro)(ems are s"i(( mi$or. ! "hese pro)(ems go u$$o"ice&, "hey ca$ #ery soo$ )ecome ma*or pro)(ems,

(ea&i$g "o (eaks, p(uggi$g o! co$&e$sa"e (i$es or ca"as"rophic )oi(er"u)e !ai(ure. Ii"hou" proper

corrosio$mo$i"ori$g proce&ures i$ p(ace, s"eam sys"ems ca$ ha#e u$&er(yi$g issues "ha" persis" !or(o$g perio&s o! "ime. epe$&i$g o$ "he "rea"me$" me"ho&, co$&e$sa"e mo$i"ori$g ca$ #ary, )u"

ge$era((y, "he !o((o3i$g "es"s are re'uire&D

1. p= "es"i$g a" #arious (oca"io$s i$ "he co$&e$sa"e sys"em

2. Measureme$" o! iro$ (e#e(s i$ "he co$&e$sa"e

. Measureme$" o! resi&ua( ami$e i$ "he co$&e$sa"e

8. Corrosio$ coupo$s

Evaluating p." is $ecessary "o "es" "he co$&e$sa"e6s p= "o &e"ermi$e i! i" is high e$ough "o pre#e$"

car)o$icaci& corrosio$ !rom occurri$g. Co$&e$sa"e p= measureme$" shou(& )e carrie& ou" a" more

"ha$ o$e (oca"io$, "o e$sure "ha" car)o$ic aci& &oes $o" a""ack &i!!ere$"(y i$ separa"e sec"io$s o! "he

sys"em. This ca$ happe$ 3he$ $eu"ra(i%i$g ami$es 3i"h (o3 &is"ri)u"io$ ra"ios -(ike morpho(i$e/ are

use& 3i"h mu("ip(e co$&e$sa"io$ si"es.

Ihi(e co((ec"i$g co$&e$sa"e samp(es, i" shou(& )e e$sure& "ha" e4posure "o air is mi$imi%e&, a$& "ha"

"he p= "es" is ru$ as 'uick(y as possi)(e. +(so, "he samp(e shou(& )e 3e(( coo(e& o"her3ise, C72 a$&

ami$e ca$ )o"h !(ash o!! o! a ho" samp(e, a("eri$g "he p=. + p= o! >. or higher shou(& )e "arge"e&.

!ron measurement. ro$, as a corrosio$ )ypro&uc", is a$ i$&irec" i$&ica"or o! ei"her (o3 p= or "he

prese$ce o! 72 some3here ups"ream o! "he co$&e$sa"e samp(i$g poi$". ! "his area is $o" )ei$g checke&

!or p= measureme$"s, iro$ measureme$" shou(& )e &o$e. The samp(e shou(& )e !rom a co$"i$uous(y

!(o3i$g s"ream "o a#oi& a s(ug o! iro$ o4i&e !rom "he ope$i$g o! a #a(#e. + #a(#e 3hich is ope$e& !rom


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a c(ose& posi"io$ -3hi(e "aki$g a samp(e/ ca$ re(ease a s(ug o! iro$ 3hich 3as si""i$g ups"ream o! "he

c(ose& #a(#e. There are "hree &i!!ere$" "es"s "ha" ca$ )e ru$, !or 3hich proprie"ary me"ho&s o! "es"i$g

are a#ai(a)(e. The suspe$&e&iro$ "es" measures i$so(u)(e suspe$&e& iro$ )y passi$g "he samp(e

"hrough a mem)ra$e !i("er. ;uspe$&e& iro$, mos"(y !erric iro$ -Fe27 or Fe78, 3hich is Fe27 H Fe7/ is

"he resu(" o! a$ o4i&i%i$g co$&i"io$ i$ "he co$&e$sa"e. The poi$" o! "his "es" is "o i$&ica"e "he prese$ceo! 72 i$ "he sys"em, ei"her "hrough impro#e& &eaera"io$ or "he use o! )e""er 72 sca#e$gi$g i$ "he )oi(er.

;uspe$&e& iro$ (e#e(s i$ e4cess o! 50 par"s per )i((io$ -pp)/ are i$&ica"i#e o! serious corrosio$

• The "o"a( !errous a$& !erric iro$ "es" measures )o"h &isso(#e& iro$ -mos"(y !errous/ a$&

suspe$&e& iro$ -mos"(y !erric/. ! a mem)ra$e !i("er is use& "o remo#e "he suspe$&e& iro$, "he

"es" 3i(( measure &isso(#e& iro$. For mos" i$&us"ries, a "es" resu(" o! 0.5 par"s per mi((io$

-ppm/ is co$si&ere& a goo& "es" resu("

• The "o"a( iro$ "es" a((o3s !or "racki$g "o"a( iro$ o#er "ime 3i"hou" regar& !or o4i&a"io$ s"a"e.

This "es" pro#i&es #a(ua)(e !ee&)ack a)ou" "he e!!ec"i#e$ess o! "he ami$e "rea"me$" program

o! "he co$&e$sa"e

"esidual filming amine and O2 scavengers. ! a !i(mi$g ami$e is u"i(i%e&, "he resi&ua( shou(& )e

measure&. +s s"a"e& ear(ier, "he mos" commo$ !i(mi$g ami$e !or )oi(ers is oc"a&ecy(ami$e. " shou(& )e

measure& o$ a s"eam samp(e $o" a co$&e$sa"e samp(e. osage ca$ )e co$"ro((e& "o gi#e 0.2K0.9

ppm oc"a&ecy(ami$e i$ s"eam. 7c"a&ecy(ami$e is mos" e!!ec"i#e i$ co$&e$sa"e 3i"h a p= ra$ge o! 9 "o

>. Thus, "he pro&uc" may re'uire supp(eme$"a( $eu"ra(i%i$g ami$e "o )e a&&e&. + coo(i$g coi( is

re'uire& &uri$g samp(i$g "o pre#e$" s"eam !rom !(ashi$g o!!, 3hich 3i(( co$ce$"ra"e "he ami$e i$ "he

samp(e. ;imi(ar(y, 72 sca#e$ger co$ce$"ra"io$ mus" )e precise 3i"hi$ "he sys"em. ! =+ is use&, a

resi&ua( o! 100K150 pp) shou(& )e "arge"e& 5 G. This resi&ua( 'ua$"i"y 3i(( "ake some "ime "o appear,as "he =+ 3i(( i$i"ia((y )e co$sume& i$ passi#a"i$g "he sys"em. + coo(i$g coi( shou(& )e use& !or

co((ec"i$g "he samp(e "o a#oi& (oss o! #o(a"i(e chemica(s i! "here is s"eam !(ashi$g.

Corrosion coupons.re3eighe& s"rips o! me"a( -coupo$s/ 3i"h #ery simi(ar composi"io$ "o "he

me"a((urgy o! "he co$&e$sa"e sys"em ca$ )e use& "o mo$i"or "he corrosio$ ra"e. Corrosio$ coupo$ racks

"ha" ho(& "hree coupo$s are ge$era((y use&. 7$e coupo$ is e4pose& !or 0 &ays, o$e !or 90 &ays a$& o$e

!or @0 &ays. The coupo$s are remo#e& !or each "ime i$"er#a(, a$& "he 3eigh" (oss o! "he coupo$ is

&e"ermi$e&. From "he o)ser#e& 3eigh" &e"eriora"io$ i$ "he coupo$, "he corrosio$ ra"e is ca(cu(a"e& i$

mi(s -0.0001 i$./ per year -mpy/. N


27/27

Edited by Mary Page Bailey

REFERENCES

1. Bre$$er, M.+., =o3 ;"eam ;ys"em Chemis"ry a$& Co$"ro( +!!ec" ;"eam ;i&e Coi( Corrosio$,

Ies"er$ ry Ai($ +ssocia"io$ Mee"i$g rocee&i$gs, or"(a$&, 7reg., May 2008.

2. eaera"i$g Boi(er Fee&3a"er, =+C $gi$eeri$g,333.hpac.comOhea"i$gO)oi(er!ee&3a"er , +pri(

200>.

. Be"% La)ora"ories $c., Be"% $&us"ria( Ia"er Co$&i"io$i$g, @"h e&., ;ep". 1@@1.

8. =y&roser#e, Typica( Boi(er Pues"io$s,333.hy&roser#e.comO)oi(er'ues"io$s.h"m.

5. Jamaica +ssocia"io$ o! ;ugar Tech$o(ogis"s, ;ugar Boi(er Ia"er Trea"me$"

Tech$o(ogy,333.*amaicasugar.orgOsiri;ec"io$O*as"O*as"papersOpapersOy2010O)oi(er

mitigate corrosion in condensate

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