FE270 Section 11 (NXPowerLite).ppt-Cathodic

Cathodic Protection

1. Haward Technology Middle East 1Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Section 11
Impressed Current Cathodic
Protection Design for Plant

2. Haward Technology Middle East 2Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Impressed Current Cathodic Protection
Current
O
2 OH
-
IMPRESSED
CURRENT
ANODE
PIPE
Transformer
Rectifier
Powerelectrons
Electrical
connections
Drain
point
V
-ve +ve

3. Haward Technology Middle East 3Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Impressed Current CP Anodes
Scrap iron
Graphite
High Silicon Iron
Magnetite
Titanium Oxide (LEDA)
Lead/Silver
Platinum on Titanium
Platinum on Niobium

4. Haward Technology Middle East 4Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Impressed Current CP Anodes
Scrap iron
Graphite
High Silicon Iron (14% Si)
Magnetite
Titanium Oxide (LEDA)
Lead/Silver
Platinum on Titanium
Platinum on Niobium
Consumption
10 kg/Ay
0.5 – 1 kg/Ay
0.2 – 0.7 kg/Ay
0.03 kg/Ay
0.003 kg/Ay
0.004 kg/Ay
10
-5
kg/Ay
10
-5
kg/Ay

5. Haward Technology Middle East 5Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Anode Fabrication
Rubber or
resin fill
and cap
Silicon iron
or graphite
anode
Copper conductor
Titanium/niobium
or tantalum sheath
2 - 5 microns
platinum deposit
~50% cover
Plastic clad
conductor
Plastic clad
conductor

6. Haward Technology Middle East 6Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Ground Bed Arrangements
Single horizontal
anode chain
Parallel array of
horizontal anodes
Parallel array of
vertical anodes
Single vertical
anode chain

7. Haward Technology Middle East 7Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Deep Ground Bed
Protective
current

8. Haward Technology Middle East 8Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Equivalent Circuit
R
anode
R
SOIL
R
cathode
R
pipeline
R
circuit
E

9. Haward Technology Middle East 9Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Chlorine Generation
Excessive chlorine from deep wells
The narrow bore area of the deep wells means that the
composition of the water can change slightly over time,
becoming more acid and higher salinity.
At the anode the reactions are:
Cl
-
+ H
2
O – 2e = 2H
+
+ OCl
-

10. Haward Technology Middle East 10Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Desalination Plant
C
u
r
r
e
n
t

D
e
n
s
i
t
y

m
A
/
m
2
Salinity %2 4 86
150
70
Carbon steel
-900 mV SSCE
0.3 m/s
35 oC
Current Density vv Salinity

11. Haward Technology Middle East 11Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Desalination Plant
C
u
r
r
e
n
t

D
e
n
s
i
t
y
m
A
/
m
2
Flow velocity m/s
0.03 0.3 3
100
700
Carbon Steel
Copper Nickel Aluminium
50
Seawater 30,000 ppm
30
o
C
-900 mV SSCE

12. Haward Technology Middle East 12Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Water flow rate
C
o
r
r
o
s
i
o
n

r
a
t
e
~Re
0.2
~Re
0.8
S
t
a
g
n
a
n
t
General
Corrosion
Erosion
Corrosion
Cavitation
API RP-14E
criterion

13. Haward Technology Middle East 13Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Desalination Plant
C
u
r
r
e
n
t

D
e
n
s
i
t
y
m
A
/
m
2
700
150
Temperature
o
C
10040
Carbon steel
Seawater 100,000 ppm
-900 mV SSCE
Velocity 0.5 m/s

14. Haward Technology Middle East 14Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Compressor Stations
Remove all unnecessary buried steelwork
Take account of materials selection at design
Coat all buried metallic items
Use a quality coating
Use ground mats/rods that are anodic to steel
Avoid shielding of buried items
Minimize the number of isolation fittings
Install test points at areas of concern

15. Haward Technology Middle East 15Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
Domestic Water Heaters
Protected Material Life Expectancy of a 1 kg magnesium anode
1 m x 26 mm dia 40
o
C
Offset 10 cm Offset 30 cm Offset 50 cm
Steel 1 1.8 2.5
Galvanized steel 1.7 3.2 4.5
Copper 0.8 1.4 2.0
Bronze 1.0 1.6 2.3
Galvanized steel 2%
cb’down
1.6 2.9 4.1
Stove enameled
steel 2% cb’down
11.5 13.5 14.7

16. Haward Technology Middle East 16Section 11
Cathodic Protection Systems: Design,
Fabrication, Installation, Operation and Repair
End of this
Section