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مدیر وبلاگ : pc7a
نویسندگان
CATHODIC PROTECTION SYSTEM
PRECOMMISSIONING AND
COMMISSIONING PROCEDURE
CONTRACT NO.:
PROJECT:
SOUTH PARS GAS FIELD DEVELOPMENT
32" INTER-PHASE PIPELINE
PHASES 6, 7 & 8 TO PHASES 9 & 10
COMPANY: NATIONAL IRANIAN OIL COMPANY
SITE: ASSALUYEH /SOUTH PARS GAS FIELD
PERSIAN GULF, IRAN
1
1‐ PRE‐COMMISSIONING INSPECTION & CHECK
1‐1‐ All checks, tests and measurements shall be carried out by contractor in the present
of COMPANY or representative before commissioning test, this is to ensure as far as
practicable that all the requirements of the contract has been carried out and
installation is ready for Pre‐commissioning. The contract requires that the test
carried out shall not in any way be a danger to person, property or equipment.
Contractor shall provide all equipment, meters and accessories for conducting tests
and measurements.
Prior to final commissioning all involved/neighbor owners shall be informed.
1‐2‐ All provision such as testing equipment, special tools and coordination for
availability of power and all pertinent work permits shall be envisaged.
1‐3‐ A program shall be provided for Pre‐commissioning test with the approval of
engineer and client.
1‐4‐ Related procedure and tables for Pre‐commissioning check as attached as appendix"
A" and as described below:
1‐4‐1‐ Deep well ground bed check list (close type).
1‐4‐2‐ Test box and test bond box check list.
1‐4‐3‐ Positive bond box check list.
1‐4‐4‐ Zinc anode check list.
1‐4‐5‐ Zinc earthing cell check list.
1‐4‐6‐ Spark gap check list.
1‐4‐7‐ Current control box check list.
1‐4‐8‐ Transformer rectifier check list.
1‐4‐9‐ Transformer rectifier earthing system check list.
1‐4‐10‐ Ac box check list.
1‐4‐11‐ Structure/Electrolyte natural potential surrey.
1‐4‐12‐ Insulating joint check list.
1‐4‐13‐ CP circuit resistance check list.
3
Note: Megger test & cable continuity test and cable labeling shall be checked and the
results shall be filled in the appendix "A" tables.
1‐5‐ Following is the list of tools that is required to this stage.
1‐5‐1‐ High impedance multimeters:
Voltmeters for DC volts and millivolts measurements may be analogue or
digital with an input impedance of 10 Mega ohms or more. An instrument
with lower input impedance may produce valid data if circuit contact errors
are considered.
1‐5‐2‐ Portable CU/CUso4 reference electrode:
All cathodic protection potential readings involve the use of a reference
electrode or half cell. The purpose of which is to make a reproducible
connection between the meter and the electrolyte.
The reference is reasonably accurate (within 5 mv when measured against a
reference electrode known to be free of contamination).
1‐5‐3‐ Electrical tool kit.
1‐5‐4‐ Mechanical tool kit.
1‐5‐5‐ Megger and earth tester.
1‐6‐ Applicable standards:
BS 7361: Part 1 Cathodic Protection, Part 1, Code of Practice for Land and Marine
Applications.
NACE‐RP‐0169 Control of External Corrosion of Underground or
Submerged Metallic Piping System.
NACE‐RP‐0572 Design, Installation Operation and Maintenance
Of Impressed Current Deep well Ground beds.
4
NACE‐TM‐0497 Measurement Techniques Related to Criteria for Cathodic
Protection on Underground or Submerged Metallic Piping
Systems.
2‐ COMMISSIONING OF CATHODIC PROTECTION SYSTEM
2‐1‐ INTRODUCTION
This procedure indicates the stages at witch tests shall be made for commissioning of
cathodic protection system. Commissioning tests, described in the following, shall be
carried out after successful completion of various operation and pre‐commissioning tests.
The effectiveness of a cathodic protection installation depends on applying and
maintaining the correct potential difference between the structure and the adjacent
environment at all parts of the structure.
2‐2‐COMMISSIONING REPORT
The contractor shall submit a commissioning report to the client for review of obtained
data after switching on all CP systems.
2‐3‐ COMMISSIONING SURVEY
The commissioning survey shall include the following tests and measurements, where
applicable, to ensure that the structure is protected in accordance with the design criteria,
and that all equipment is correctly installed and functioning correctly:
2‐3‐1‐ Measurement of ON/OFF pipeline to soil potentials at all test stations of the
pipeline. Data for effectiveness of insulating joints shall also be obtained
during these measurements.
2‐3‐2‐ Interference test with other buried or immersed installations shall be
measured after switching on the impressed current cathodic protection
system, including mitigation of if required.
5
2‐3‐3‐ Final adjustment of the output of the DC power if required, after reviewing the
data obtained by above noted tests and by considering that:
‐ After sufficient polarization of pipeline, the output of each CP system should
be optimized regarding the potential shift in relation to the current output.
‐ All sections/parts of the concerned structure/system should be in
accordance with the specified design data for the cathodic protection.
2‐3‐4‐ First of all, voltage of all test points shall be read when the system is on. If
measured potentials of two test points, which are next to each other, is out of
design criteria, the CIPS test shall be done between those two test points.
After correction and removing errors, protection potentials shall be read again.
2‐3‐5‐ Recording of finally adjusted details of CP systems and performance
parameters, as required, in the enclosed forms.
2‐4‐ COMMISSIONING TEST PROCEDURE
2‐4‐1‐ If there is time gap between pre‐commissioning and final commissioning
(maximum 3 month); all tests conducted during pre‐commissioning shall be
repeated for final check and record the data.
2‐4‐2‐ Check and confirm availability, safety and voltage of A.C supply to transformer
rectifier, energize the transformer rectifier and perform functional test. Check
for signs of distress such as excessive transformer noise, smoke, burning, odors
and etc. If signs of distress occur, immediately switch the unit off, and re‐check
positive and negative D.C cables for connection faults.
2‐4‐3‐ Adjust the output voltage and current to its minimum level and switch on the
transformer on the load and then gradually increase the current and voltage
level. Adjust the current level as per design or at level below that to achieve an
on‐potential of ‐1500mV with respect to Cu‐CuSO4 reference electrode.
2‐4‐4‐ The transformer rectifiers shall be energized for a minimum period of 72
hours before any measurements are taken. It is important that stabilization
shall be achieved before the remainder of commissioning proceeds. If
6
required, adjust outputs at transformer rectifiers as required(Potential shall be
measured after 24 & 48 hours and On/Off potential shall be measured after 72
hours).
2‐4‐5‐ variable resistors should be used to balance the current to each of the
adjacent pipelines, if required.
2‐4‐6‐ During the polarization period the current output of the transformer rectifier
shall be progressively reduced to maintain the steel to soil potential at its
desired level. Also during the polarization period, regular check of structure
potential and transformer rectifier output shall be made in order to avoid over
protection.
2‐4‐7‐ For reading the potential the reference electrode shall be located in contact
with surface of the earth directly over or not more than six pipe diameters
away from the structure along the surface of the earth at selected locations.
2‐4‐8‐ The cathodic protection system shall achieve the ‐0.85 (V) instant off (free of
IR drop) protection level on protected buried pipelines with respect to a
saturated CU/CUSO4 reference electrode.
2‐4‐9‐ The contractor shall not perform any tests that would either void the vendor
warranty or damage the materials and equipment.
2‐4‐10‐ In order to measure a more true potential the current shall be switched off
momentarily, the potential (the off potential) shall be measured immediately
after interruption. For this purpose set the timer unit of transformer rectifier
for operation of current interruption and select a suitable switching cycling.
Measure and record energized “on” and interrupted “off” line potentials at
test facilities. The “off” potentials shall represent the IR error free pipe to soil
potential.
The "off" cycle should be kept as short as possible but still long enough to read
a polarized pipe to electrolyte potential. Excessive delay results in the existing
protection level being underestimated due to depolarization. Periods during
which the measurement can be made ranging from 0.1 to 3s have been
suggested. The measurements are carried out with the cathodic protection
7
switched off and on at intervals; in most cases a ratio of 1 off: 4 on, will not
introduce significant depolarization.
Two transformator shall be capable to be on and off synchronizely during
commissioning.
2‐4‐11‐ Measure and record all system currents, voltages and set potentials as
applicable.
2‐5‐INTERFERENCE TEST
Interference from cathodic protection system arises where a foreign structure intersects
the direct current path between the anode and cathode. Interference tests shall be carried
out at all crossings with foreign buried pipelines. Interference test shall be carried with the
understanding that the criterion is the swing of the potential of the foreign structure from
the natural value. Interference tests including mitigation of if required, in accordance with
the details given below:
a) The foreign structure‐to‐electrolyte potential shall be taken while the transformer
rectifiers of this project are switched on and switched off.
b) If the foreign pipeline is cathodically protected the effect of the foreign pipeline
to the project pipeline must be tested while the CP system of the foreign pipeline
is switched on and switched off.
Where testing of a cathodic protection installation indicates that there is interference at a
level which may result in corrosion of the foreign structure, control of the interference may
be achieved by taking the following actions.
a) Installing galvanic anodes or an impressed current system on the foreign
structure.
b) Bonding the foreign structure to the primary structure through a current
controlling resistance, if appropriate.
c) Insulating the foreign structure.
f) Reducing the cathodic protection system current.
8
Interference mitigation by bonding the effected structure shall be carried out if:
‐ Change in the natural potential of a structure/pipeline, measured with a CU/CUSO4
reference electrode placed on the soil above the foreign structure, is more than
100mV in the positive direction in accordance with the applicable regulations, or
20mV, if the reference electrode is placed direct beside the pipe‐surface of
investigated pipeline.
‐ The existing more electronegative than ‐0.85 V structure‐to‐soil potential
(measured as polarization (off) potential with a CU/CUSO4 electrode placed on the
soil above the structure ) of a structure/protected by some other cathodic protection
station is made more electropositive than ‐0.85 V.
At crossing the potential shall be measured while the half cell electrode is placed directly
over the crossing point and results shall be registered at attached check list as
Appendix "B".
In case that interference is indicated and the measured potential shift exceeds the
limitations according to specification, then these measurements shall be followed by
the measurements of potentials at 5 m spacing over a distance of 50 m in the
upstream and downstream directions of each pipeline.
Potential measurements shall be registered at attached check list as Appendix "C".
The magnitude and direction of current in the bond connection shall be measured
and recorded. The control resistor shall be adjusted so that a minimum amount of
current is flowing in the bond, to fulfill the acceptable limits of specification.
9
2‐6‐TEST SEQUENCE
Specific details and sequence of commissioning tests for each category of protected
pipeline system defined in document are given in the following.
2‐6‐1‐ Review the data obtained during the system operation and
Pre‐ commissioning tests.
2‐6‐2‐ Measure the pipeline‐to soil potentials during on and switched‐off conditions
of the DC power units. The potentials shall be measured at all test point, drain points and
insulating joints.
‐ Review the on/off potential data and determine: effectiveness of insulating joints
and take remedial measures, if required.
‐ Need for conducting interference tests and remedial measures.
2‐6‐3‐ Adjust output of the DC power unit, if required.
2‐6‐4‐ Record all system particulars and test details, as required, in the enclosed
forms. Additionally the pipe to soil potential data shall be presented in graphical form.
2‐6‐5‐ The final commissioning is completed if all tests have been successfully
completed and the protection criteria are reached.
2‐6‐6‐ Put the system in commercial operation if protection criteria is reached.
10
Appendix 'A'
Pre-Commissioning procedure
This procedure covers the inspection & tests regarding the pre-commissioning activities of cathodic protection system for
underground pipelines as described below:
1.DEEP WELL GROUNDBED CHECK LIST (CLOSE TYPE):
- Visual inspection for installation of equipments.
- Electrical check for Resistance measuring.
2.TEST BOX & TEST BOND BOX CHECK LIST:
- Visual inspection for installation of support & box.
- Electrical check for cable connection & wiring.
3.POSITIVE BOND BOX CHECK LIST:
- Visual inspection for installation of support & box.
- Electrical check for cable connection & wiring.
4.ZINC ANODE CHECK LIST:
- Visual inspection for cable connection.
- Measuring open circuit potential of Zinc electrode.
5.ZINC EARTHING CELL CHECK LIST:
- Visual inspection for cable connection.
- Measuring open circuit potential of Zinc electrodes.
6.SPARK GAP CHECK LIST:
- Electrical check for cable connection & wiring.
7.CURRENT CONTROL BOX CHECK LIST:
-Visual inspection for installation of support & box.
-Electrical check for cable connection & wiring.
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8.TRANSFORMER RECTIFIER CHECK LIST:
- Visual inspection for installation.
- Electrical check for cable connection & wiring.
9.TRANSFORMER RECTIFIER EARTHING SYSTEM CHECK LIST:
- Visual inspection for installation.
- Electrical check for cable connection & wiring.
10.AC BOX CHECK LIST:
- Visual inspection for installation of support & box.
- Electrical check for cable connection & wiring.
11. STRUCTURE/ ELECTROLYTE POTENTIAL SURVEY:
Test method: (in accordance with BS7361- part 1- sub clause 10.6.3)
a survey shall be carried out to determine the structure/electrolyte potential variation along, or over the surface of the structure,
Employing a suitable reference electrode & Voltmeter. Such a set of potential measurements may indicate those points on the
structure where the worst corrosion is likely to be taking place.
With no applied cathodic protection and in the absence of stray currents, the most negative structure/ electrolyte potentials
indicate the corroding areas. On the other hand, If corrosion is due predominantly to stray Current in the soil, the more intense
corrosion will be associated with the more positive structure/ electrolyte potentials.
12. INSULATING JOINT CHECK LIST:
- Electrical check of two side of insulating joint potentials.
13. CP CIRCUIT RESISTANCE CHECK LIST:
-Electrical check of CP circuit resistance.
12





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