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INTEGRATED REDEVELOPMENT PROJECT
TITLE: CATHODIC PROTECTION
PREPARED: AIBA
CHECK: MAA
SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
PIPELINE CATHODIC PROTECTION SYSTEM DESIGN
(DnV RP B401 2021)
References:
1) DnV RP B401, Cathodic Protection Design (2021)
2) ISO 15589-2, Cathodic Protection of Pipeline Transportation Systems
TITLE: CATHODIC PROTECTION SYSTEM FOR PMAPL092 FWS FLEXIBLE PIPELINE
1.0)INPUT DATA
1.1)General Pipeline Data
Outer diameter of pipeline
Do := 433.64 mm
Inner diameter of pipeline
Di := 254  mm
Length of Pipeline
L := 1000 m
Steel pipeline anti-corrosion coating thickness
Ec := 5.5 mm
Insulation material thickness
Ins := 0 mm
Clearance between anode and pipeline
Clearance := 0  mm
Concrete coating thickness
Ct := 0  mm
Water depth
WD := 65 m
1.2)Service Data
Design life in years
t f := 25 yr
Design Safety Factor
fs := 1.0
Design Life multiplied by Design Safety Factor
t fd := t f  fs = 25
Anode Surface Temperature (OC)
Ta := 50
Anode surface temperature is taken
from Heat Transfer Calculation sheet
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SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
1.3)Environmental Data
Exposure Condition
(if Buried EC=1.0; if Non-Buried=2.0)
Environmental Resistivity
EC := 2.0
ρe := 0.23 ohm m
DNV RP B401, Figure 8-1
1.4)Electrochemical Data
Anode Material
(if aluminum = 0, if zinc = 1)
Design Protective Potential
Anode Potential
Mat := 0
Eca := -0.8
 VV
1.05
DNV RP B401, Section 2.4.1
DNV RP B401, Table 8-6
AP :=
if Mat = 0
( -1050) if Ta  30  EC = 2.0
( -1000) if Ta  30  EC = 1.0
( -1050) if 31  Ta  60  EC = 2.0
( -1000) if 31  Ta  60  EC = 1.0
( -1000) if 61  Ta  80  EC = 2.0
( -1000) if 61  Ta  80  EC = 1.0
if Mat = 1
( -1030) if Ta  30  EC = 2.0
( -980 ) if Ta  30  EC = 1.0
( -1030) if 31  Ta  50  EC = 2.0
( -980 ) if 31  Ta  50  EC = 1.0
"Wrong Input" otherwise
3
AP = -1.05  10
Ea := AP mV
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Design Closed Anode Potential
Ea = -1.05 V
DNV RP B401, Table 8-6
Driving Voltage
ΔE := Ec - Ea
DNV RP B401, Section 4.8.2
ΔE = 0.25 V
Anode Electrochemical Capacity
DNV RP B401, Table 8-6
ε c.mat :=
if Mat = 0
( 2000) if Ta  30  EC = 2.0
( 1500) if Ta  30  EC = 1.0
( 1500) if 31  Ta  60  EC = 2.0
( 680) if 31  Ta  60  EC = 1.0
( 720) if 61  Ta  80  EC = 2.0
( 320) if 61  Ta  80  EC = 1.0
if Mat = 1
( 780) if Ta  30  EC = 2.0
( 750) if Ta  30  EC = 1.0
( 780) if 31  Ta  50  EC = 2.0
( 580) if 31  Ta  50  EC = 1.0
"Wrong Input" otherwise
Anode Electrochemical Capacity
function to temperature
as a
ε c := ε c.mat
A  hr
kg
3
ε c = 1.5  10  A
Bracelet Anode Utilisation Factor
u := 0.8
hr
DNV RP B401,Figure 6.6.1
kg
DNV RP B401, Table 6.9.1
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FLEXIBLE PIPELINE
DNV RP B401, Table 8-1
and Table 8-2
Initial current density
i ci :=
-2
0.15 A m
if 0  WD  30 m
-2
0.12 A m
if 31 m  WD  100  m
-2
0.14 A m
if 101  m  WD  300  m
-2
0.18 A m
if WD  300  m
-2
i ci = 0.12 A m
Mean current density
i cm :=
-2
0.07 A m
-2
0.06 A m
-2
0.07 A m
-2
0.09 A m
if 0  WD  30 m
if 31 m  WD  100  m
if 101  m  WD  300  m
if WD  300  m
-2
i cm = 0.06 A m
Final current density
i cf :=
-2
0.1 A m
-2
0.08 A m
-2
0.09 A m
-2
0.13 A m
-2
i cf = 0.08 A m
if 0  WD  30 m
if 31 m  WD  100  m
if 101  m  WD  300  m
if WD  300  m
PROVISION OF ENGINEERING FOR SEPAT
INTEGRATED REDEVELOPMENT PROJECT
TITLE: CATHODIC PROTECTION
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SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
DNV RP B401, Section 3.3.9
Include allowance for temp.>25oC
i ci :=
(
)
i ci if Ta  25
i + T - 25  0.001 A  otherwise
)
 ci ( a
2
m 

(shall be increased by 0.001A/m2 for each oC)
i ci = 0.15
i cm :=
A
2
m
(
)
i cm if Ta  25
i + T - 25  0.001 A  otherwise
)
 cm ( a
2
m 

i cm = 0.09
i cf :=
A
2
m
(
)
i cf if Ta  25
i + T - 25  0.001 A  otherwise
)
 cf ( a
2
m 

i cf = 0.11
A
2
m
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TITLE: CATHODIC PROTECTION
SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
1.5)End-Fitting
Length of End Fitting
LEf := 1084 mm
Outer Diameter of End Fitting
ODEf := 596.08 mm
Inner Diameter of End Fitting
IDEf := Do
1.6)Flexible Pipeline Tear-Off
Outer Diameter of Tensile Armour
Exposed to Seawater
ODTa := 355.6 mm
IDTa := 345.44 mm
t Ta := ODTa - ID Ta
PREPARED: AIBA
CHECK: MAA
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INTEGRATED REDEVELOPMENT PROJECT
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SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
2.0)CALCULATIONS
2.1)Coating Breakdown Factor Calculation
Area of Flexible Pipe Tear-Off
ATo := π ODTa ( 0.05 L)
2
ATo = 55.86 m
Area of Exposed End Fitting
 OD 2 - ID 2
Ef 
 Ef
AEf := 2  π
+ π ODEf  LEf
4
2
AEf = 2.29 m
Initial Coating Breakdown Factor
k1 := 0.002
ISO 15589-2, Table 3
Average Yearly Increase Coating
Breakdown Factor
k2 := 0.0001
Average Coating Breakdown Factor
(End Fitting)
fcm_Ef := 1
DNV RP B401, Section 3.4.1
Average Coating Breakdown Factor
(Tear-Off)
fcm_To := k1 + 0.5 k2  t f
DNV RP B401, Section 3.4.2
-3
fcm_To = 3.25  10
Final Coating Breakdown Factor (End Fitting)
fcf_Ef := 1
Final Coating Breakdown Factor (Tear-Off)
fcf_To := k1 + k2  t f
DNV RP B401, Section 3.4.1
-3
fcf_To = 4.5  10
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SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
2.2)Current Demand Calculations
Average Current Demand (End Fitting)
Icm_Ef := AEf  fcm_Ef  i cm = 0.19 A
Average Current Demand (Tear-Off)
Icm_To := ATo  fcm_To i cm = 0.02 A
Total Average Current Demand
Icm.Total := Icm_Ef + Icm_To
Icm.Total = 0.21 A
Final Current Demand (End Fitting)
Icf_Ef := AEf  fcf_Ef  i cf = 0.24 A
Final Current Demand (Tear-Off)
Icf_To := ATo fcf_To i cf = 0.03 A
Total Final Current Demand
Icf.Total := Icf_Ef + Icf_To
Icf.Total = 0.27 A
2.3)Anode Mass Calculation
Anode Material Mass calculation
required for design life
M :=
Icm.Total  t fd  8760 hr
u εc
M = 38.38kg
-3
Anode Material Density
ρanode := 2750 kg m
Anode Material Volume
V :=
M
ρanode
7
3
V = 1.4  10  mm
DNV RP B401, Eq (4.2)
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SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
2.4)Anode Selection
Nominal Gap between two half
shell anodes
Gap := 75mm
Thickness of bracelet anode body
wbracelet := 40mm
Anode Internal Diameter
ID := Do + ( 2  Ec ) + ( 2  Ins) + ( 2  Clearance)
ID = 444.64 mm
Anode Outer Diameter
OD := ID + 2  wbracelet
OD = 524.64 mm
Anode Length
Volume of Bracelet Anode
(including flat bar core and rod bar insert
but excluding the taper volume)
Lbracelet := 400mm
 π  OD


 -  ID    L
Vanode := 2   
  
bracelet - 2  wbracelet Gap Lbracelet
2
2
2
2
 

2



7
3
Vanode = 2.2  10  mm
Taper End Thickness
t t := Ct - Ins - Clearance
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t t = 0 mm
Taper Length
Note
: For bracelet anode, taper end
thickness (tt) equal to thickness
l t := 0mm
of bracelet anode (wbracelet).
Taper length (lt) equal to zero.
Total Length of Anode
()
Anodelength := Lbracelet + 2 l t
Anodelength = 400 mm
Volume of Taper End
(half anode body)
(
)
1
π
2
2
2
Vtaper :=
 π l t  OD + OD ID + ID -   ID  l t
12
4

3
Vtaper = 0  mm
Width of Flat Bar Core
Bbar := 25mm
Thickness of Flat Bar Core
wbar := 5  mm
Thickness of first layer of Anode Material
(under the flat bar core)
wFL := 3  mm
Flat Bar Core Internal Diameter
IDbar := ID + 2  wFL
(
)
IDbar = 450.64 mm
Flat Bar Core Outer Diameter
ODbar := IDbar + 2  wbar
ODbar = 460.64 mm
Volume of Flat Bar Core
2
2
  OD

 IDbar  
π 
bar 
Vbar := 2   
 -
   Bbar
 2  2   2  

5
3
Vbar = 1.79  10  mm
Distance of Flat Bar Core
from end of Lbracelet [l]
DisFBC := 20mm

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FLEXIBLE PIPELINE
Distance of Rod Bar Insert from
end of Flat Bar Core width [m]
DisRBI := 10mm
Length of Rod Bar Insert
Lplate := Lbracelet - 2  DisFBC - 2 DisRBI
(
)
(
)
Lplate = 340  mm
Diameter of Rod Bar Insert
Dplate := 5  mm
Number of Rod Bar Insert ( for half anode body)
Numplate := 3
Volume of Rod Bar Insert
(2 halves anode body)
2
 D

 plate 
Vplate := 2  Numplate π 
  Lplate
  2 

4
3
Vplate = 4.01  10  mm
Volume of Anode Material only
(bracelet anode)
Vbracelet := Vanode - Vbar - Vplate
7
3
Vbracelet = 2.17  10  mm
Net Volume of Anode Material
Vnet := Vbracelet + 2  Vtaper
7
3
Vnet = 2.17  10  mm
Net Mass of Anode Material
(excluding flat bar core and rod bar insert)
M net := ρanode Vnet
M net = 59.79 kg
Note:The Net Mass of Anode Material ( M net) in Section 2.4 must be equal to or greater than Anode Material
Mass (M) in Section 2.3
Check Net Mass of Anode Material ( M net)
Mass Check :=  "OK" if M net  M


 "CHECK" if M > M net 


equal to or greater than Anode Material (M)
Mass Check = "OK"
NoAnode_Req :=
(
M
M net
)
ceil NoAnode_Req = 1
= 0.64
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FLEXIBLE PIPELINE
2.5)Final Anode Thickness
The final anode thickness is based on the 0.8 usage factor carried out on the unit volume using the
cross-sectional area.
π
2
2
Vinital :=  ( OD) - ( ID)  - 2  wbracelet Gap
4
Cross-section area of anode
4
2
Vinital = 5.49  10  mm
Guess t f := 1mm
Vfinal := ( 1 - u)  Vinital
Given
π
2
2
Vfinal =   Do + 2  Ec + 2  t f - Do + 2  Ec  - 2t f  Gap

4 
(
) (
)
( )
t f := Find t f
Final anode thickness
Ratio of final anode thickness over inital
anode thickness
t f = 8.62 mm
tf
wbracelet
= 21.55 %
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2.6)Final Current Demand
Final Exposed Surface Area
(bracelet anode)
 ID + 2 tf 
  Lbracelet
2


SAbracelet := 2  π 
5
2
SAbracelet = 5.8  10  mm
Final Exposed Surface Area
(taper end)
2
 ID + 2  tf ID   ID + 2  tf ID 
2
SAtaper := π 
+
 
 + lt
2
2  
2
2 

4
2
SAtaper = 1.23  10  mm
Total Anode Surface Area
SAtotal :=
(SAbracelet + 2 SAtaper) if lt > 0
SAbracelet otherwise
5
2
SAtotal = 5.8  10  mm
Final Anode Resistance
Rafinal :=
0.315 ρe
DNV RP B401, Table 8-7
SAtotal
Rafinal = 0.1 Ω
Final Current Output
ΔE
Ia :=
Rafinal
DNV RP B401, Eq (4.3)
Ia = 2.63 A
Total Final Current Demand
Icf.Total = 0.27 A
Check Final Output > Final Demand
FinalCheck :=
"OK" if Ia > Icf.Total
"CHECK!" if Ia < Icf.Total
FinalCheck = "OK"
PROVISION OF ENGINEERING FOR SEPAT
INTEGRATED REDEVELOPMENT PROJECT
TITLE: CATHODIC PROTECTION
PREPARED: AIBA
CHECK: MAA
SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
2.7)Attenuation
Resistivity of Pipe Wall Material
-6
ρMe := 0.2 10
 ohm m
Attenuation Length
Lat :=
(
2t Ta ODTa - t Ta
ISO 15589-2, Eq (B.4)
)  -Ra
ρMe ODTa fcf_To i cm 



final i cm π ODTa fcf_To +
(Rafinal)  ( icm) π  ODTa  fcf_To ...
2
+
2 2
ρMe i cm fcf_To ODTa
2
2
(
t Ta ( ODTa - t Ta)
 Ec - Ea
)



3
Lat = 4.97  10 m
AttenuationCheck :=
"OK!" if Lat > L
"CHECK!" if Lat < L
AttenuationCheck = "OK!"
2.8)Crack Propensity Ratio
Crack Propensity Ratio
CPR :=
Anodelength  ID π
-1
5mm
3
 wbracelet
CPR = 1.75
It is advisable that the ratio of inner diameter, thickness and length to be adjusted to ensure a CPR value of 5 or less. This
will ensure less probability of cracks during anode manufacture.
PROVISION OF ENGINEERING FOR SEPAT
INTEGRATED REDEVELOPMENT PROJECT
TITLE: CATHODIC PROTECTION
PREPARED: AIBA
CHECK: MAA
SYSTEM FOR PMAPL090 FWS
FLEXIBLE PIPELINE
2.9)Summary of Anode Selection
Anode O.D
(mm) [a]
524.64
Anode I.D
(mm) [b]
444.64
Total Length
(mm) [c]
400
Taper Length
(mm)
0
Description
Design Life (including design factor)
Mass of One Anode
Mean Current
Total Net Anode Mass Required
Mean Current Demand Check
Total Final Current Demand
Final
Final Current Output
Current
Final Current Demand Check
Flexible Pipe Length
Attenuation
Attenuation Length
Attenuation Check
Thickness
(mm) [d]
40
Symbol
tfd
M net
M
MassCheck
IcfTotal
Ia
FinalCheck
L
Lat
AttenuationCheck
Units
yr
kg
kg
A
A
m
m
-
Nominal Gap
(mm) [e]
75
Value
25
38.38
59.79
OK
0.27
2.63
OK
1000
4973
OK!
Width of FBC Thickness of FBC
Length of RBI Diameter of RBI
FBC O.D (mm) [h] FBC I.D (mm) [i]
(mm) [f]
(mm) [g]
(mm) [j]
(mm) [k]
25
Note :
5
460.64
1) FBC = Flat bar core
2) RBI = Rod bar insert
3) Quantity of anodes excluding the anodes for riser.
450.64
340
5
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2.9)Anode Sketch
Note :
1) [l] = Distance of Flat Bar Core from end of Lbracelet
2) [m] = Distance of Rod Bar Insert from end of Flat
Bar Core width.