AKARYAKIT VE KMYASAL MADDE DEPOLAMA TANKLARINDA

A05.02.2014ISSUED FOR INFORMATIONM.C.Z.K.E.D.

Rev.DateDescriptionPreparedCheckedApproved

No.ORIGINATOR

EDOPEC ENERJ PETROL MHENDSLK SANAY VE TCARET LMTED RKET

Head Office :

Palmiye Mah. Adnan menderes Bulv. Oktay Sitesi No: 9/8 PK = 33100 Yeniehir /Mersin TURKEY

P:+90 324 3260595

F:+90 324 3260596

Ankara Office :

UUR MUMCU CAD(krolu cad) ERDL APT 87/13 Gop-ankaya -Ankara-TURKYEP: +90 312 447 17 18 / 20F:+90 312 447 17 21

stanbul Office:Burhanye Mahalles amlca Caddesi

hlamur villalar no 28 / 6^RD3K Villa ^ Beylerbeyi skdar stanbul / TURKEY

P : +90 216 4220414 PBX

F: +90 216 4220415

www.edopec.com. info@edopec.comDocument TitleBAKU - TBILISI - CEYHAN CRUDE OIL PIPELINE PROJECT Lot B

Document No.

EDPWMSCOECORINTXXX014178206Rev

AScale

Co. Org. CodDoc TypeDisc. CodeUnit CodePrj. TypePrj.

NOPrj.

YearPrj Seq.NoDCC Seq.NoPage16

table of contents

31scope

42codes and standards

53DESCRIPTION

64SITE EQUIPMENTS and Man POWER

75MethodOLOGY

75.1Survey Procedure

76AUTHORITY AND PERMITS REQUIREMENTS

77LAND ACQUISITION REQUIREMENTS

78H&S REQUIREMENTS

79ENVIRONMENT ASSESSMENT

710COMMUNITY RELATIONS ASSESSEMENTS

711SECURITY ASSESSEMENT

712QA / QC

1. scopeThis Work Method Statement is prepared for DC Voltage Gradient Survey (DCVG Survey) on BTC LOT-B crude oil pipeline.

DC Voltage Gradient Survey (DCVG Survey) is carried out on buried pipelines to locate and assess the severity of coating defects.

2. codes and standards

BS-736Cathodic Protection Part 1: Code of Practice for Land and Marine Applications

IEEE 81Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounded System

NACE RP0169Control of External Corrosion on Underground or Submerged Metallic Piping Systems

NACE RP0190External Protective Coatings for Joints, Fittings, and Valves on Metallic Underground or Submerged Pipelines and Piping Systems

NACE RP0274

High Voltage Electrical Inspection of Pipeline Coating Prior to Installation

NACE RP0286

The Electrical Isolation of Cathodically Protected Pipelines

NACE RP0572

Design, Installation, Operation and Maintenance of Impressed Current Deep Ground Beds

NACE RP0792

Standard Format for Computerized Close Internal Survey Data

3. DESCRIPTION

The Direct Current Voltage Gradient (DCVG) is a technique for coating surveys on buried pipelines. It has been used for not only locating but also sizing coating defects. The technique is fundamentally based on measuring the voltage gradients in the soil above a buried pipeline.

4. SITE EQUIPMENTS and Man POWER

High sensitivity centre zero voltmeter.

Current Interrupter (suitable for current to be interrupted and with a switching speed compatible with the survey meter).

Reference (Ski) probes compatible with the survey meter.

Temporary dc current source and ground bed equipment (required if pipeline not protected by impressed current or system cannot be interrupted).

Depending on the number of crew; for one crew a man who is used to the survey technique to evaluate results in the field can undertake the DCVG survey. An assistant may be required in difficult terrain and one 4x4 vehicle would be necessary.

5. MethodOLOGY

The system works by the application of a cyclically switched d.c. current to the pipeline and measurement of the magnitude and direction of the voltage gradients in the soil.

Either an existing or a temporary impressed current system is used as a source of d.c. current to the pipeline. The d.c. source is interrupted cyclically, usually about the ratio 2:1 (off:on). This provides a rapidly pulsing d.c. source that can be easily identified with an analogue millivoltmeter.

Special measurement instruments are required that are able to respond to the rapidly changing voltage. The analogue instrument is centre zeroed so that the direction, as well as the magnitude, of the pulsing d.c. voltage can be measured.

The d.c. voltage gradients are measured by placing reference electrodes on the ground about 1 m to 1,5m apart. The operator usually walks parallel to the pipeline, placing the reference electrodes on the ground about every 2 m, and observing the analogue instrument indication.

When the d.c. current flows to a coating defect the potential gradient in the soil will change, becoming greater as the defect is approached, and decreasing to zero when the epicentre of the coating defect is mid-way between the two reference electrodes.

There are many variations that can be applied in the field, and the correct interpretation of the measured data is dependent upon the competence of the operator.

The defects found during a DCVG survey can be mapped by GPS coordinates and will fully documented on special developed defect sheets.5.1 Survey Procedure

Prior to commencement of any survey section a current interrupter is installed in the existing cathodic protection stations or temporary current source which may be established as necessary.

Typically, a minimum potential swing of 500-600 mV is sought and the current source output is adjusted accordingly. The application of a pulsed current enables coating defects to be distinguished from stray traction and telluric currents.

The difference between 'on' and 'off' potentials is recorded at the test point nearest the survey start point, and all other test points encountered, and the survey commenced.

The operator traverses the pipeline route using the probes as walking sticks. One probe is in contact with the ground at all times and for a short duration between strides both probes must be in ground contact. One probe can be on the centerline of the pipeline and the other maintained at a lateral separation of 1-2 m or probes can leap-frog along the centre line. If no defects are present the needle on the voltmeter registers no movement.

As a defect is approached a noticeable fluctuation is observed on the voltmeter at a rate similar to the interruption cycle. The amplitude of the fluctuation increases as the defect is approached and adjustment of voltmeter sensitivity is made as necessary. The swing on the voltmeter is directional, providing the probes are maintained in similar orientation parallel to the pipeline.

Thus, the defect is centered by detailed maneuver around the epicenter and the size of the defect estimated by considering signal strength at the defect, difference between 'on' and 'off' potential at adjacent test point and the distance from those points.

A sensitive milli-voltmeter and two copper-copper sulfate reference electrodes (placed about one meter apart by the operator) are typically used for measuring purposes.The nature of the milli-voltmeter signal during a DCVG survey is illustrated in the diagram below, in relation to the defect epicenter.

6. AUTHORITY AND PERMITS REQUIREMENTS

The Natural Gas Pipeline and NATO Pipelines rectifiers must be turned off during the DCVG Survey. If any such additional permits to be obtained, the same will be obtained in accordance with the requirements.

7. LAND ACQUISITION REQUIREMENTS

Presently no additional land requirement is foreseen, if any such requirement an addendum will be prepared and submitted to Employer for approval.

8. H&S REQUIREMENTS

Refer attached JSEA and Risk assessments .

9. ENVIRONMENT ASSESSMENT

No special environmental assessments is required any how

All environmental incidents will be reported.

All debris and waste materials will be removed from the easement each working day to Employer approved location.

Toilet facilities will be provided on the easement at all times.

10. COMMUNITY RELATIONS ASSESSEMENTS

Whenever and wherever the COL department service required, they will be informed in advance in a timely manner to carry out their work.

11. SECURITY ASSESSEMENT

None.

12. QA / QC

All the works will be carried out in accordance with approved procedure and specifications.