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RELIEF SYSTEMS IN PROCESS PLANTS
ARE THEY NEEDED?
RELIEF SYSTEM
SAFETY INTERLOCKSYSTEM
ALARM SYSTEM
BASIC PROCESSCONTROL SYSTEM
Could
these all
fail due
to a
o!!o"
fault?
Hi"t# Yes$$
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RELIEF SYSTEMS IN PROCESS PLANTS
RELIEF SYSTEM
SAFETY INTERLOCKSYSTEM
ALARM SYSTEM
BASIC PROCESSCONTROL SYSTEM
Loatio"
E%ui&!e"t seletio"
Dou!e"ti"' o"
d(a)i"'s
Ma*i!u! a&ait+
,hat-s i" thisto&i?
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RELIEF SYSTEMS IN PROCESS PLANTS
$ I"(ease i" &(essu(e a" lead to (u&tu(e of .essel o( &i&e
a"d (elease of to*i o( fla!!a/le !ate(ial
0 Also1 )e !ust &(otet a'ai"st u"e*&eted .auu!$
$Natu(all+1 /est to &(e.e"t the &(essu(e i"(ease
0 la('e distu(/a"es1 e%ui&!e"t failu(e1 hu!a" e((o(1
&o)e( failu(e1 222
$ Relief s+ste!s &(o.ide a" e*it &ath fo( fluid
$ Be"efits# safet+1 e".i(o"!e"tal &(otetio"1 e%ui&!e"t
&(otetio"1 (edued i"su(a"e1 o!&lia"e )ith
'o.e("!e"tal ode
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STANDARD RELIEF METHODS
$ BASIC PRINCIPLE: No external power required -self atuati"' 0pressure of process proides needed force!
$ 7AL7ES- close w"en pressure returns to accepta#le alue
- Relief $ale - liquid s%ste&s
- Safet% $ale - 'as and apor s%ste&s includin' stea&
- Safet% Relief $ale - liquid and(or apor s%ste&s
$ Pressure of protected
s%ste& can exceedt"e set pressure)
Copyrights by CCPS/American Institute of Chemical Engineers and copied with the permission of AIChE
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STANDARD RELIEF METHODS
$ BASIC PRINCIPLE: No external power required -self ati"'
$ R8PT8RE DISKS OR B8RST DIAPHRA9MS-&ust #e replaced after openin'
)
Copyrights by CCPS/American Institute of
Chemical Engineers and copied with the
permission of AIChE
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SOME INFORMATION ON RELIEF 7AL7ES
$ T)o t+&es of desi'"s dete(!i"e i"flue"e of &(essu(e
i!!ediatel+ afte( the .al.e
0 Co".e"tio"al 7al.e0&(essu(e afte( the .al.e affets the
.al.e lift a"d o&e"i"'
0 Bala"ed 7al.e0 &(essu(e afte( the .al.e does "ot affet
the .al.e lift a"d o&e"i"'
Co".e"tio"al Bala"ed
Copyrights by CCPS/American Institute of Chemical Engineers and copied with the permission of AIChE
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SOME INFORMATION ON RELIEF 7AL7ES
$ AD7ANTA9ES
0 si!&le1 lo) ost a"d !a"+ o!!e(ial desi'"s a.aila/le
0 (e'ai" "o(!al &(oess o&e(atio" (a&idl+ /eause the
.al.e loses )he" &(essu(e de(eases /elo) set .alue
$ DISAD7ANTA9ES
0 a" lea6 afte( o"e /ei"' o&e" 3O0(i"' (edues4
0 "ot fo( .e(+ hi'h &(essu(es 3:;1;;; &si4
0 if o.e(si
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SOME INFORMATION ON R8PT8RE DISKS>
B8RST DIAPHRA9MS
$ A )ide (a"'e of !ate(ials a"d
desi'"s a(e a.aila/le
$ AD7ANTA9ES
0 "o lea6a'e u"til the /u(st0 (a&id (elease of &ote"tiall+ la('e .olu!es
0 hi'h &(essu(e a&&liatio"s
0 o((osio" leads to failu(e1 )hih is safe
0 !ate(ials a" /e slu((ies1 .isous1 a"d sti6+
$ DISAD7ANTA9ES
0 !ust shutdo)" the &(oess to (e&lae
0 '(eate( loss of !ate(ial th(ou'h (elief
0 &oo(e( au(a+ of (elief &(essu(e the .al.e
Copyrights by CCPS/American
Institute of Chemical Engineers and
copied with the permission of AIChE
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SHO,IN9 RELIEF SYSTEMS ON PROCESS
INSTR8MENTATION 3PI4 DRA,IN9S
S&(i"'0loaded safet+ (elief .al.e
Process
To efflue"t ha"dli"'
Ru&tu(e dis
Process To efflue"t ha"dli"'
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ADD RELIEF SYSTEM TO THE FOLLO,IN9
PROCESS DRA,IN9
F@
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ADD RELIEF SYSTEM TO THE FOLLO,IN9
PROCESS DRA,IN9
F@
The d(u! a" /e isolated
)ith the o"t(ol .al.es=
&(essu(e (elief is (e%ui(ed2
,e )ould li6e to (eo.e()ithout shutdo)"= )e
selet a (elief .al.e2
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ADD RELIEF SYSTEM TO THE FOLLO,IN9
PROCESS DRA,IN9
Positi.edis&lae!e"t
&u!&
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ADD RELIEF SYSTEM TO THE FOLLO,IN9
PROCESS DRA,IN9
Positi.edis&lae!e"t
&u!&
The &ositi.e dis&lae!e"t
&u!& )ill /e da!a'ed ifthe flo) is sto&&ed= )e
"eed to &(o.ide (elief2
,e )ould li6e to (eo.e(
)ithout shutdo)"= )e
selet a (elief .al.e2
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ADD RELIEF SYSTEM TO THE FOLLO,IN9
PROCESS DRA,IN9
,h+ a(e all
those .al.es
i" the &(oess?
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ADD RELIEF SYSTEM TO THE FOLLO,IN9
PROCESS DRA,IN9
The e*t(a ha"d.al.es
e"a/le us to isolate a"d
(e!o.e the heat e*ha"'e(
)ithout sto&&i"' the&(oess2
The shell side of the heat
e*ha"'e( a" /e isolated=
)e "eed to &(o.ide (elief2
,e )ould li6e to (eo.e(
)ithout shutdo)"= )e
selet a (elief .al.e2
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Copyrights by CCPS/American Institute of Chemical Engineers and copied with the permission of AIChE
IN SOME CASES1 RELIEF 7AL7E AND
DIAPHRA9M ARE 8SED IN SERIES 0 ,HY?
,h+ is the &(essu(ei"diato( &(o.ided?
Is it loal o( (e!otel+
dis&la+ed? ,h+?
,hat is the ad.a"ta'e
of t)o i" se(ies?
,h+ "ot ha.e t)o
(elief .al.es
3dia&h(a'!s4 i"
se(ies?
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Copyrights by CCPS/American Institute of Chemical Engineers and copied with the permission of AIChE
IN SOME CASES1 RELIEF 7AL7E AND
DIAPHRA9M ARE 8SED IN SERIES 0 ,HY?
,h+ is the &(essu(e
i"diato( &(o.ided?
If the &(essu(e i"(eases1
the dis6 has a lea6 a"d
should /e (e&laed2
Is it loal o( (e!otel+
dis&la+ed? ,h+?
The dis&la+ is loal to
(edue ost1 /eause )e
do "ot ha.e to (es&o"d
i!!ediatel+ to a failed
dis6 0 the situatio" is "ot
ha
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Copyrights by CCPS/American Institute of Chemical Engineers and copied with the permission of AIChE
*E S+,L. ALS, PR,/EC/ A0AINS/
E1CESSI$E $AC2
The follo)i"' e*a!&le uses /u6li"' &i"s
o.e(&(essu(e
u"de(&(essu(e
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SOME 7APOR AND D8ST EPLOSIONS RE8IRE
7ENTS
$ Co"t(ol a"d di(et the e*&losio" affets
Structure ent closed
Structure
explosion
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,E M8ST SAFELY PROCESS OR DISPLOSE
OF MATERIAL FROM RELIEF SYSTEM$
F(o!(elief
To e".i(o"!e"t 7e"t stea!1 ai(
Holdi"' fo( late( &(oessi"' ,aste )ate( t(eati"'
Re+le to &(oess Fuel 'as1 fuel oil1 sol.e"t
Reo.e( &a(t to &(oess
I!!ediate "eut(ali
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Copyrights by CCPS/American Institute of Chemical Engineers and copied with the permission of AIChE
,E M8ST SAFELY PROCESS OR DISPLOSE
OF MATERIAL FROM RELIEF SYSTEM$
A &(oess e*a!&le )ith se.e(al fo(!s of efflue"t ha"dli"'
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SI5IN9 RELIEF SYSTEMS
$ DETERMINE THE RELIEF FLO, 3!a*i!u!
&ossi/le4
$ DETERMINE THE SET PRESS8RE
0 /ased o" &(oess "eeds a"d e%ui&!e"t !ate(ials a"do"st(utio"
$ SELECT THE RELIEF TYPE
0 /ased o" ad.a"ta'es>disad.a"ta'es of /oth
$ CALC8LATE THE NEEDED AREA FOR FLO,
$ SELECT THE COMMERCIAL DE7ICE FROM
7ENDOR=S SPECIFICATIONS
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DETERMININ9 FLO,S FOR SIMPLE SIT8ATIONS
Fi" Fout ?
Fout ?
Tsou(e T
Relief Flo)Sou(e
Fout ?
Li%uid o( .a&o(filled s+ste!
T)o0&hases+ste! )ithheat i"&ut
Li%uid s+ste!)ith "o &haseha"'e a"d)ith heatt(a"sfe(
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DETERMININ9 FLO,S FOR SIMPLE SIT8ATIONS
Fi" Fout ?
Fout ?
Tsou(e T
Relief Flo)Sou(e
Fout ?
Li%uid o( .a&o(filled s+ste!
T)o0&hases+ste! )ithheat i"&ut
Filled Li%uid s+ste!)ith "o &haseha"'e a"d)ith heatt(a"sfe(
Fi"
37'07l4>
H.a&
>
C&
,hat is the !eha"is! fo( heat t(a"sfe(? Radiatio" o(
o".etio"?
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DETERMINE THE MAIM8M FLO, FOR THE
O7ERHEAD 7APOR
8"de( )hat
o"ditio"s is the
.a&o( at its
!a*i!u!?3
4
q
R
.
B
LC
LC
PC
A
1.
A1B
$
Relief
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DETERMINE THE MAIM8M FLO, FOR THE
O7ERHEAD 7APOR
Relief
The !a*i!u! .a&o(
ou(s )he"
@2 Ma*i!u! feed .a&o(2
:2 Ma*i!u! (e/oile( dut+2
G2 Co!&lete loss of
o"de"satio" 3loss of
ooli"' )ate(42
3
4
q
R
.
B
LC
LC
PC
A
1.
A
1B
$
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DETERMINE THE MAIM8M FLO, FOR THE
RELIEF SYSTEM
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DETERMINE THE MAIM8M FLO, FOR THE
RELIEF SYSTEM
I" additio" to the
shell0side fluid1 )e
!ust o"side( the
&ossi/ilit+ of a lea6
f(o! the tu/e side2
This !i'ht /e a la('e
flo) o( (e%ui(e s&eial
&(oessi"' /eause of
ha
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DETERMININ9 THE AREA FOR 7AL7ES IN LI8ID
SER7ICE
$ Basi e%uatio" fo( flo)
th(ou'h a" o(ifie
$ Rea((a"'e to sol.e fo(
a(ea a"d add o((etio"
fato(s
Ps set &(essu(e = P/ /a6 &(essu(e
K..isosit+ o((etio" 3 @2; as Re la('e1 G;1;;;4
K&o.e(&(essu(e o((etio"1 de&e"ds o" the o.e(&(essu(e f(o! (elief de.ie
3lo)e( o.e(&(essu(e 'i.es a s!alle( K& a"d la('e( a(ea4
K//a6 &(essu(e o((etio"1 @2; fo( /ala"ed .al.e
@2; fo( o".e"tio"al .al.e
Pg2AC=F
c
!P"P#g2
$$$C
F=A
bscbp%
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DETERMININ9 THE AREA FOR DIAPHRA9MS IN
7APOR SER7ICE
$ Basi e%uatio" fo( flo) th(ou'h a" o(ifie .e"ti"' toat!os&he(e
$ Rea((a"'e to sol.e fo(
a(ea )ithout o((etio"
fato(s
,hat s&eial fato(
is i!&o(ta"t i" the
dia&h(a'! (elie.i"' to
a (eo.e(+ s+ste!?
Pg2AC=F
c
/o flare
Liquid
recoer%
5),)dru&
Burstdiap"ra'&
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DETERMININ9 THE AREAS FOR 7AL7ES AND
DIAPHRA9MS IN 7APOR OR 9AS SER7ICE
$ Ofte"1 the flo) is so"i o( Aho6ed@0 i" this situatio"1the flo) de&e"ds o" the u&st(ea! &(essu(e /ut "ot the
do)"st(ea! &(essu(e2 This ou(s )he" Ps ;2P/= this is
(ou'h esti!ate1 see (efe(e"es2
$ The defi"i"' e%uatio" is
,ith KJ de&e"di"' o" T1 heat a&ait+ (atio1 !ol2 )ei'ht1 /a6
&(essu(e1 a"d o!&(essi/ilit+
uestio"# Ho) do )e 6"o) if the flo) is ho6ed?
Does this !ea" that a" i"(ease i" /a6 &(essu(e has "o effet o" flo)?
PA$=Fcho&edJ
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DETERMININ9 THE AREAS FOR 7AL7ES AND
DIAPHRA9MS
FOR EOTHERMIC REACTORS
CA8TION$
$ T)o0&hase .e"ti"' has &(o.ed diffiult to !odel (elia/l+
0 DIERS1 3Desi'" I"st2 fo( E!e('e"+ Relief S+ste!s4fo(!ed /+
o!&a"ies a"d AIChE0 'oals a(e to dete(!i"e si
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DETERMININ9 THE AREAS FOR 7AL7ES AND
DIAPHRA9MS
FOR EOTHERMIC REACTORS
CA8TION$
$ A sta"da(d e*&e(i!e"tal a&&a(atus is used to ollet adia/ati data o"
(u"a)a+ (eatio"s
0 s!all sale so little ha
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SA3E/6 RELIE3 S6S/E2S7
*+A/ +A$E *E LEARNE.8
These a(e self0atuated1 "o e*te("al &o)e( is (e%ui(ed
T)o !ao( de.ies a(e (elief .al.e a"d (u&tu(e dis6
Relief is (e%ui(ed fo( all losed .olu!es
,e !ust di.e(t !ate(ial to a ade%uate ha"dli"'
s+ste!
,e a(e "o) (ead+ to 'ai" e*&e(ie"e i" desi'"i"' a"d
e.aluati"' safet+ (elief s+ste!s2
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REFERENCES
Andrew7 *) and +) *illia&s7 Applied Instru&entation in t"e Process Industries7 $olu&e I: A Sure%7 0ulf
Pu#lis"in'7 +ouston7 9;
Andrew7 *) and +) *illia&s7 Applied Instru&entation in t"e Process Industries7 $olu&e II: Practical
0uidelines7 0ulf Pu#lis"in'7 +ouston7 9) Louar7 7 C"e&ical Process Safet%: 3unda&entals wit" Applications7 Prentice +all7
En'lewood Cliffs7 9=
.ris?ell7 L)7 Control $ale Selection and Si@in'7 Instru&ent Societ% of A&erica7 9) Leun'7 New Experi&ental /ec"nique for C"aracteri@in' Runawa% C"e&ical Reactions7
CEP7 p) -7 Au'ust 9enett7 E)7 .esi'n Considerations for Pressure-Reliein' S%ste&s7 C"e&) En'r)7 Part I7 p) 9D-9=7 >ul%
9F Part II7 p) 9D9-9D
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RELIEF SYSTEM LEARNIN9 TASKS
@2 Re.ie) the CCPS ,,, !ate(ial
3o" ou(se site i" (est(ited a(ea4
Lesso" @2 Relief Re%ui(ed
Lesso" :2 Ru"a)a+ Reatio"s
Lesso" G2 Safe'ua(ds 3e*&losio"s4
:2 Re.ie) this lesso" a"d solutio"s2
G2 Read Pe((+-s Ha"d/oo61 se.e"th Editio"1
&2 :0: to :0G1 :0G to :0
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RELIEF SYSTEM ,ORKSHOP
@2 Re.ie) the distillatio" &(oess o" the "e*t &a'e2
:2 Loate se.e(al (elief s+ste!s2
G2 E.aluate eah s+ste! fo( &(o&e( loatio" a"dhoie of (elief de.ie
2 Fi"d a loatio" that should ha.e a (elief s+ste! /ut
does "ot2
Re!e!/e(1 the fi'u(e ould ha.e e((o(s fo(
teahi"'>lea("i"' &u(&oses2
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