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G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES



TABLE OF CONTENTS


1.0
INTRODUCTION

2.0 SUMMARY

3.0
SOIL RESISTIVITY SURVEY

4.0 DESIGN PARAMETERS

5.0
CATHODIC PROTECTION DESIGN CALCULATIONS

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G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

0




c:

1.0 INTRODUCTION

This report defines the design calculations and requirements of Cathodic Protection System
for one No. 17" existing gas pipeline and three new LPG product pipelines. An impressed
current cathodic protection system will be installed to supplement the' corrosion coating in
providing corrosion control to the pipeline. The impressed current Cathodic Protection
system for existing gas pipeline will be upgraded to suit the new requirement for existing
gas pipeline as well as new LPG product pipelines.

2.0 SUMMARY

Cathodic protection is specified for the onshore section of the subject pipeline from Dinh
Co to Thi Vai for new LPG pipeline and from Long Hi to Phu My for existing gas pipeline-
length and other parameters are as given in Secsion 4.0 of this document. Both galvanic
anode and impressed current cathodic protection systems were considered during this
design. An impressed current cathodic protection system has been selected on a technical
basis. The cathodic protection system has been designed in accordance with internationally
accepted standards and compliance the codes and standards listed in section
1.2
o

specification. A conservation design approach has been used including a 30 mA/m2 current
density and 95% coating efficiency. For future addition a 20% spare output capacity has
been provided
( NACE-1967). It has been determined that a single impressed current
system required upgrading at the Phuoc Hoa LBV and at the Dinh Co Station would
provide full cathodic protection of new LPG pipelines and existing gas pipelines.

The soil resistivities at this location justified the installation of an effective surface anode
groundbed. The groundbed will be located approximately
100
m from the pipeline and
position perpendicularly to the pipeline in accordance with the project specification
(BS-7361 ). A rectifier will be used to energize the groundbed. They.415. VAC; three phases
power supply to the rectifier will be provided from the
�
415;volt switchboard. Elec€rical
isolation of the pipeline will be provided by the installation of insulating flange sets
Insulating flange set shall be provided with Explosion-proof surge diverters to prevent
damage due to lightning or power surges. Test stations will be provided to monitor and
adjust the cathodic protection system . Test station also have to be provided at following
location
• Both side of the major river or road crosing.
• At all insulating joint.
• At HT overhead line crossing.
•
At all vulnerable location where interferance is possible
These test stations will be located at maximum intervals of 1.5 km. All cable connections to
the pipeline will be made using the brassing thermit weld process.

3.0 SOIL RESISTIVITY SURVEY

Soil resistivity measurements have been previously carried out by others at
65
location
along the pipeline ROW. According to the information included in the contract documents.
this testing was performed using the Wenner 4-pin method at depth of 0.75,
1.5, and
metres using a .M-416 instrument made in the Soviet Union. Test equipment must have
maximum AC & DC ground current rejection feature. Soil resistivities are critical to the
proper design of a cathodic protection system. They are used as a guide to determine the
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G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

corrosiveness of the soil and also used to select ground locations and configurations. Soil
resistivities are important regardless of whether and impressed current or a sacrificial anode
cathodic protection system is utilized. It should be understood that this cathodic protection
design has been based on the soil resistivities determined by others. Any inaccuracies in the
reported resistivity values versus the actual resistivity values could have a significant impact
on
the effectiveness of the cathodic protection system. This can only be determined during
commissioning of the system when the Contractor shall check the.soil resitivity inspection
accordance with specification.

4.0

4.1




4.1.1



Y







•

DESIGN PARAMETERS

The following sub-sections include parameters which have been used for design of the
proposed cathodic protection system.

GENERAL PIPELINE DETAILS
These calculation for upgrading existing CP system for new LPG pipelines and existing gas
pipeline will be done through two (2) cathodic protection system design.

Portion 1: (CP Station at Dinh Co location )

Gas pipeline (Long Hai to Ba Ria)

Length of pipeline
16.5
km
a
Pipeline diameter 406.4 mm
1
/17
Pipeline number
1
Coating
Coal tar enamel

LPG pipelines (Dinh Co to Ba Ria)

Length of pipeline
7.5 km
Pipeline diameter
168 mm
C L
�

Pipeline number
3
Coating Polyethylene

4.1.2

Portion 2: (CP Station at Phuoc Hoa location )

Gas pipeline (Ba Ria to Phu My)

Length of pipeline 21.5 km
Pipeline diameter
426 mm
Pipeline number
Coating
Coal tar enamel

LPG pipelines (Ba Ria to Thi Vai)

Length of pipeline
17 km
Pipeline diameter
168 mm
Pipeline number
3
P9-CPS.05-01.0

Page 4 of I '
Rev. D

/,(





G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

Coating Polyethylene

4.2
CATHODIC PROTECTION DESIGN LIFE
In accordance with the contract documents, the impressed current cathodic protection
system will have a design life of 30 years. The cathodic protection Contractor shall
demonstrate the design life of his proposed CP system.

4.3 ANODE TYPE
1
T' 'um tubular anodes with a mixed metal oxide coating will be installed. These anodes
have proven to have superior operating characteristics over silicon iron and graphite anodes.
Titanium / mixed metal oxide anode are also of lighter weight and capable of significantly
higher current outputs and longer life.

4.4
COATING EFFICIENCY
A common method to assess the pipe coating condition is to use a factor referred to
"percent bare". For a normal factory applied coaltar enamel coating system which would be
inspected and repaired prior to back filling. of the pipe, a value of a approximately I to 2
percent bare would be experienced immediately subsequent to construction. However,
during the service life of the pipeline with expansion and contraction of the pipeline due to
thermal effects, soil movement, water ingress through the coating etc, the condition of the
coating will deteriorate.
A conservative coating efficiency of 95% has been used for this cathodic protection design.
This means that over the 30 year life, the cathodic protection system will have the capacity
protect an average of 5% of the total surface area of the pipeline.

4.5 CP CURRENT DENSITY

The National Association of Corrosion Engineers
(NACE) Recommended practice
RP-0169-92 and DNV RP B401 specifies a current density of 10-30 mA/m2 for bare steel
structures in soil. The soils along the proposed ROW for this pipeline are very aggressive
with high moisture content, high salinity and low soil resistivity. Therefore, this design uses
a
conservative 30 mAIm2 current density.

4.6
SOIL RESISTIVITY

4.6.1
Dinh Co Location

As mentioned in previous Section 3.0, soil resistivity testing along the pipeline ROW has
been previously carried out by others. A review of this data indicates that points R-18 and
R-19 are located relatively near Dinh Co:

Depth (m)
Soil Resistivity (ohm cm)
R-18
0.75
8000
1.50
4200
P9-CPS.05-01.0
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G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES


3.00 1050
R-19
0.75

3600
1.50
1300
3.00
500

The deep-well anode system will be installed for cathodic protection, The average resistivity
value for the above two points at a 1.5m depth is 2750 ohm-cm and will be used t For
groundbed design at Dinh Co.

4.6.2 Phuoc Hoa Location

Also mentioned in previous Section 3.0, soil resistivity testing along the pipeline ROW has
been previously carried out by others. A review of this data indicates that points BH23 aid
BH24 are located relatively near Ba Ria ( at Phuoc Hoa ) where the impressed current CP
system will be located. The soil resistivity values reported at these locations are :

Depth (m)
Soil Resistivity (ohm ern)

BH23
0.75 1300
1.50
1500
3.00 1000

BH24
0.75 1500
1.50
1500

3.00
800

The average resistivity value for the above two points at a 1.5m depth is 1500 ohm-cnl _:d
will be used for groundbed design at Phuoc Hoa.

4.7
CATHODIC PROTECTION CRITERIA

NACE Recommended Practice RP-0169-92
addresses cathodic protection criteria
Dr
underground and submerged metallic piping systems. Applicable excerpts of this st.and=d
relative to CP criteria
for
this project are as follows-
A negative (cathodic) potential of at least
85OmV with the cathodic protecti'Dn
applied. This potential is measured with respect to a saturated copper / copper ulfat.e
reference electrode contacting the electrolyte. Voltage drops other than those across
the structure to electrolyte boundary must be considered for valid interpretation of
this voltage measurement.

A negative polarized potential of at least
850 mV relative to a saturated copper
/
copper sulfate reference electrode.

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G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

A minimum of 100 mA of cathodic polarization between the structure surface and a
stable reference electrode contacting the electrolyte. The formation or decay of
polarization can be'measured to satisfy this criterion.

5.0 CATHODIC PROTECTION DESIGN CALCULATIONS

5.1 DINH CO LOCATION

5.1.1 Pipeline Total Surface Area

The onshore portion of Long Hai to Ba Ria gas pipeline and Dinh Co to Ba Ria LPG
pipelines has a total surface area as follows:

Sa = (Pi) (d) (1)
Sa
(3.1416)-[(0.406,x 16500) + (3 x 0.168 x 7500)]
Sa
=
32921
(m2)

Where: Sa = Surface area (m2 )

Pi
= 3.1416
1
Length of pipeline (m)
Diameter of pipeline (m)

5.1.2
CATHODIC PROTECTION CURRENT REQUIREMENT

The cathodic protection system will have a DC output capacity as follows:

(Sa) (Id)
(Cb)
It


It


It
=
ZSF
1000
(32921) (30) (0.05)
X1.1
1000

54.32 (A)

Say 55 amperes

Where: Sa
Total surface area (m2 )
Id =
CP current density
(mA/m2 )
Cb
=
Coating breakdown factor (%)
SF = Safety factor (1.1)


5.1.3
CATHODIC PROTECTION ANODE REQUIREMENT

Chosen output rating of 2 Ampere for each anode, the number of anodes:

N = It/2
=
54.32/2
= 27.16
No. of anodes based on current requirement

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m.1

G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

N = 30
Another, maximum anode current output for each anodeto be determined as follows :
LogL= 3.3 - LogId
Where : L = design life in years
Id = Maximum anode current density (A/m2 )
For L = 3 0 years
The anode has a dimension of 31.75mm dia x I000mm legth with a.total area of 0.1m2
Therefore,
Id =.66.5 A/m2
Maximum current output of anode = 0.1m2 x 66.5 A/m2 =6.65A
Hence 3 0 anodes will give 6.65 x3 0 = 199.5 A > Required 54.3 2 A
noe wegt requ
id re
,
W
=


W
W
=
(0)
(It)(y)
Uf

0.1
(54.32)

(30)
0.6
271.6 kg
Anodes No. required based on weight requirement :
N
W/Wa
271.6 / 20
13.6
No. of anodes based on weight requirement, N
=
14
Where Q Anode consumption rate (kg/amp-year)
It
= Cathodic Protection current ( A )
Y = Design life of the system ( years )
Uf
= Anode Utilization factor ( 0.6 for a conservative design )
Wa = Weight of individual anode ( kg )
Hence anode No. chosen is 30

There are 20 canister anodes in existing groundbed at Dinh Co, so that 10 canister anodes
which are the same existing anode specification will be required to add in this location.

5.1.4 GROUNDBED RESISTANCE

Installation of 30 canister anodes on 5 metre spacing in 2750 ohm-cm soil results in an
estimated groundbed resistance of 0.5844 ohm as follows:

Rn = RI
+ R2 ( NACE - 1967, page 95 )

Where Rl
Anode to backfill resistance
R2 Backfill to soil resistance

Pb
BLcr - 1+ 2La
R1
N.yLcrx6.28
[In
do
S
In(0.656N)])
{
NACE - 1967 )

R1' =
50
F
n (8)(100)
I + (2)(100)
ln(0.656)(30)]
(30)(100)
(6.28)
3175 500

Ri 0.0152 (ohm)

Rev. D

-





G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES



Where:
Pb
La
=
da
=
S
=
N



Backfill resistivity (ohm-cm)
Length of anode- excluding backfill (cm)
Diameter of anode- excluding backfill (cm)
Spacing of anodes (cm)
Number of anodes


Ps

8Lc -1 +
2Lc
R2


R2
NxLcx6.28

2750
[In
In(0.656N)J)
(NACE - 196J )
do
S

(8) (150) (2) (150)
-1 +
in(0.656)(30)
J
(30)(150)
(6.28) [in 76 500

R2
=
0.5692 (ohm)


Where:
Ps
Soil resistivity

(ohm-cm)
Lc Length of anode- including backfill (cm)
dc
Diameter of anode- including backfill (cm)
S. Spacing of anodes (cm)
Number of anodes.

Hence Rn = 0.0152 + 0.5692
0.5844
(ohm)


5.1.5
TRANSFORMER RECTIFIER DC OUTPUT VOLTAGE

It is estimated that the transformer rectifier will require a 45
volt output to achieve :Lie
desired 54.32 ampere DC current output as follows:

It.(Rn+Rc) + Bemf
E
54.32x(0.5844 + 0.2) + 2
E 44.6 volts

Say
45 volts

Where : E Rectifier DC output voltage (volts)
It = Rectifier output current (amp)
Rn = Total groundbed resistance (ohm)

Rc
Total cable resistance (0.2 ohm)
Bemf
= Dropped voltage between pipeline and ground (-2.0 volts)
Note : Pipe to earth resistance (Rpe) has not been considered since the coating resistari :e is so
high.( >1010 ohm-mz ) that all current will pass through 5% bare areas through r±e
pipeline
coating.




Rev. D





G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

5.1.6
TRANSFORMER RECTIFIER AC INPUT

Actual DC power output required : Pd = 44.6 x 55.32
2422.672 (W)
DC power requirement including 20% overvoltage provision (20% spare Capacity )
= 1.2x44.6x54.32=2907.2 (W)
Now, considering overall system P.F (power factor) = 0.8
and Transformer Rectifier Unit efficiency (E.F) = 0.85 (85% )
For 3 phases, 415V, 50Hz supply input to Transformer Rectifier Unit :

Input current

2907.2
Ip

Ip =
Jx415x0.8x0.85

5.95 A

Hence, AC power input ( including 20% spare capacity) is :
43 x 415 x 5.95 x 0.8
3420.23 Watt

5.1.7 CHANGE IN EARTH POTENTIAL DUE TO FORCED DRAINAGE

When CP current is injected into ground through anode bed, the current flow results
in a
potential gradient in the earth.
_
The change in earth potential near the pipelines

(Ps)(It)
V
=
27r(r)

(2750)(54.32)
V

Where :
Ps
It
r

5.2
PHUOC HOA LOCATION

5.2.1
Pipeline Total Surface Area
2
7zx
10000

2.38 Volts
Soil resistivity ( ohm-cm )
Cathodic Protection current ( Ampere )
Distance between pipeline and anode bed (cm )

The onshore portion of Ba Ria to Phu My gas pipeline and Ba Ria to Thi Vai LPG pipelines
has a total surface area as follows:

Sa
_ (Pi) (d) (1)
Sa
(3.1416) [(0.426 x 21.500)+ (3 x 0.168 x 17000)]
Sa =
55691 (m2 )
P9-CPS.05-01.0

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G.U.P PHASE I1- LIQUID PIPELINES, TERMINAL & JETTIES



Where: Sa
Surface area (m2 )
Pi
3.1416
I
Length of pipeline (m)
Diameter of pipeline (m)

5.2.2
CATHODIC PROTECTION CURRENT REQUIREMENT

The cathodic protection system will have a DC output capacity as follows:

It = 91.89 A
Say 92 amperes

Where:
Sa Total surface area (m2 )
Id = CP current density (mA/m2 )
Cb = Coating breakdown factor (%)
SF = Safety factor (1.1)

5.2.3
CATHODIC PROTECTION ANODE REQUIREMENT

Chosen output rating of 2 Ampere for each anode, the number of anodes:

N
= It/2
92/2
=
45.95
No. of anodes based on current requirement

N = 50
Another, maximum anode current output for each anodeto be determined as follows :
LogL=3.3 -Log Id
Where : L = design life in years
Id = Maximum anode current density ( A/m2 )
For L = 30 years
The anode has a dimension of 31.75mm dia x 1000mm legth with a total area of 0.1m2
Therefore, Id = 66.5 A/m2

Maximum current output of anode = 0.1 m2 x 66.5 A/m2 = 6.65A
Hence 50 anodes will give 6.65 x 50 = 332.5 A > Required 92 A
(Q)(It)(Y)
Anode weight required,
W =


W
=

Uf
(0.1)
(92)
(30)
0.6
460 kg
Page I 1-of 14-
Rev. D

xSF
CbIdSa
It
1000
**)(
=
1.1
1000
05.0*30*)55691(
xIt =

G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

Anodes No. required based on weight requirement :
N
= W / Wa
460 / 20
23
No. of anodes based on weight requirement, N = 23
Where Q = Anode consumption rate (kg/amp-year )
It = Cathodic Protection current (A )
Y = Design life of the system ( years )
Uf
=
Anode Utilization factor ( 0.6 for a conservative design
Wa = Weight of individual anode ( kg )

Hence anode No. chosen is 30

There are 20 canister anodes in existing groundbed at Phuoc Hoa, so that 30 canister
anodes which are the same existing anode specification will be required to add in this
location.

5.2.4
OROUNDDED RESISTANCE

Installation of 50 canister anodes on 5 metre spacing in
1500 ohm-cm soil results in an

estimated groundbed resistance of 0.19 ohm as follows:
Rn = R1 + R2
Where
R1 =
Anode to backfill resistance
R2 Backfill to soil resistance
R1=


R1=






R1 = 0.0094 Ohm





Where: Pb
La
=
da
=
S
=
N

=

Backfill resistivity (ohm-cm)
Length of anode- excluding backfill (cm)
Diameter of anode- excluding backfill (cm)
Spacing of anodes (cm)
Number of anodes.








+−
××
)656.0(ln
2
1
8
28.6
N
S
La
da
La
Ln
LaN
Pb







+−
××
)50*656.0(ln
500
100*2
1
175.3
100*8
28.610050
50
Ln


R2=




R2 =

R2= 0.196 (ohm)

Where:.
Ps =
Soil resistivity (ohm-cm)
Lc =
Length of anode- including backfill (cm)
dc
Diameter of anode- including backfill (cm)
S Spacing of anodes (cm)
Number of anodes.

Hence Rn 0.0094 + 0.196
0.2054 (ohm)

5.2.5
TRANSFORMER RECTIFIER DC OUTPUT VOLTAGE

It is estimated that the transformer rectifier will require a 42 volt output to achieve
the desired 92mpere DC current output as follows:

It.(Rn+Rc) + Bemf
E
92 x (0.2054 + 0.2) + 2
E
39.29 volts

Say 42 volts

Where.: E Rectifier DC output voltage (volts)

it = Rectifier output current_ (amp)
Rn _ Total groundbed resistance (ohm)
Rc = Total cable resistance (0.2 ohm)
Bemf =
Dropped voltage between pipeline and ground (-2.0
volts)

Note : Pipe to earth resistance (Rpe ) has not been considered since the coating
resistance
is so high ( >1010
ohm-nag ) that all current will pass through 5% bare areas
through the
pipeline coating.





5.2.6 TRANSFORMER RECTIFIER AC INPUT

Actual DC power output required :
Pdc
= 39.29 x 92
3614.68 ( W)







+−
××
)656.0(ln
2
1
8
28.6
N
S
Lc
dc
Lc
Ln
LcN
Pb






+−
××
)50*656.0(ln
500
150*2
1
175.3
150*8
28.615050

50
Ln
DC power requirement including 20% overvoltage provision (20% spare Capacity)
= 1.2x39.29x92=4337.6 (W)
Now, considering overall system P.F ( power factor) = 0.8
and Transformer Rectifier Unit efficiency (E.F) = 0.85 ( 85% )
For 3 phases, 415V, 50Hz supply input to Transformer
Rectifier Unit : Input current

IP=





Ip =8.875 A


Hence, AC power input ( including 20% spare capacity) is :

- _

85.08.04153
6.4337
xxx
Wxxx 50138.0875.84153 =


:
G.U.P PHASE II - LIQUID PIPELINES, TERMINAL & JETTIES

5.2.7 CHANGE IN EARTH POTENTIAL DUE TO FORCED DRAINAGE

When CP current is injected into ground through anode bed, the current flow results in a
potential gradient in the earth.

The change in earth potential near the pipelines

(Ps)(It)
2 r(r)

(1500)(92)
V =




Where : Ps
=
It
=
r
=

2

π
xl0000

= 2.2 Volts

Soil resistivity ( ohm-cm )
Cathodic Protection current ( Ampere )
Distance between pipeline and anode bed ( cm )
Page 14 of 14