Dasar cathodic Portection system

Dasar cathodic protection system for presentation, dasar proteksi katodik
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INTERNATIONAL STANDARD ISO 15589-2

Foreword

ISO 15589-2:2004(E)


ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 15589-2 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC 2, Pipeline transportation systems.

ISO 15589 consists of the following parts, under the general title Petroleum and natural gas industries —
Cathodic protection of pipeline transportation systems:

— Part 1: On-land pipelines

— Part 2: Offshore pipelines


Introduction

Pipeline cathodic protection is achieved by the supply of sufficient direct current to the external pipe surface,
so that the steel-to-electrolyte potential is lowered to values at which external corrosion is reduced to an
insignificant rate.

Cathodic protection is normally used in combination with a suitable protective coating system to protect the
external surfaces of steel pipelines from corrosion.

External corrosion control in general is covered by ISO 13623.

Users of this part of ISO 15589 should be aware that further or differing requirements may be needed for
individual applications. This part of ISO 15589 is not intended to inhibit alternative equipment or engineering
solutions to be used for the individual application. This may be particularly applicable where there is innovative
or developing technology. Where an alternative is offered, any variations from this part of ISO 15589 should
be identified.

Deviations from this part of ISO 15589 may be warranted in specific situations, provided it is demonstrated
that the objectives expressed in this part of ISO 15589 have been achieved.

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Basic Calculation For Sacrificial System

A. Current requirement ( I ) = SA x CD

Where :
SA = Surface area (taken from Norton Corrosion calculation)
CD = Current density (taken from NACE standard RP 0176-83)
(Standard Recommended Practice Corrosion Control of Steel, fixed Offshore Platform
Associated with Petroleum Production)
Sea water = 55 mA.sq.m
Seabed = 11 mA/sq.m

B. Anode Weight = N

N = (I x Con x L) : U

Where,
I = Current requirement (Amp)
Con = Consumption rate of aluminium anode = 3.35 Kg/AY
Consumption rate of magnesium anode = 7.7 Kg/AY
L = Life time = 10 years
U = Utilization factor = 0.9

C. Example

Data:
Atmospheric Storage Tank:
- Length (L) : 5.54 m
- Diameter (D) : 9.058 m
- Water level Assume : 1 m
Current Density (CD) : 55 mA/m2
Consumption Rate of Aluminum Anode : 3.5 kg/Amp Year
Years design : 10 tahun
Utility Factor : 0.9

Calculation:

1 Surface Area (SA)

- Surface Area of Ground = pi x D2 = 3.14 x 82.047 = 257.62 m2
- Surface Area of wall = pi x D x L = 3.14 x 9.058 x 5.54 = 157.56 m2
Total Surface Area = 415.18 m2

2 Current Requirement (Ip)

Ip = SA x CD
= 415.18 m2 x 55 mA/m2
= 22,834.9 mA = 22.835 Amp

3 Weight of Anode (W)

W.Al = Ip x Y x 3.5 kg/Amp Year
U = 22.835 Amp x 10 years x 3.5 kg/Amp Year : 0.9
= 799.225 kgs

4 Number of Aluminium Anode (N)

Proposed Aluminium Anode type 50 kg - Net weight = 50 kg/ea
N.Al = W.Al : 50 kg
= 799.225 kgs : 50 kg
= 15.985 pcs = 16 pcs

Total = 16 pcs Aluminum Anode type 50 kg


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