agip - std transport and gathering pipelines inspections with intelligent pig

8/9/2019 AGIP - STD TRANSPORT AND GATHERING PIPELINES INSPECTIONS WITH INTELLIGENT PIG

1/28

0 Emission CORM CORM CORM March 98

REV. DESCRIPTION COMP. VERIF. APPR. DATE

Il presente documento RISERVATO ed di propriet dell'AGIP. Esso non sar mostrato a Terzi n sar utilizzato per scopi diversi da quelli per i quali stato inviato.This document is CONFIDENTIAL and the sole property of AGIP. It shall neither be shown to third partie s nor used for purposes othe r than those for which it has been sent.

DESIGN CRITERIA

TRANSPORT AND GATHERING PIPELINES

INSPECTIONS WITH INTELLIGENT PIG

14059.PLI.COR.PRG

Rev. 0

March 1998


2/28

14059.PLI.COR.PRGRev.0 March 1998Sheet 2


FOREWORD

Rev. 0 No. Sheets 28March 1998Emission


3/28



CONTENT

1 GENERAL

1.1 Scope1.2 Normative references1.2.1 European normative references1.2.2 Normative references of ISO, IEC and national organizations1.2.3 Normative references of other organizations1.2.4 Internal normative references

1.3 Definitions

2 PURPOSES OF INTELLIGENT PIG INSPECTION

2.1 Pipeline integrity assessment2.2 Corrosion monitoring

3 INTELLIGENT PIG TYPES

3.1 Classification of intelligent pigs3.2 Magnetic flux pigs3.3 Ultrasonic Pigs

3.4 Eddy Current Pigs4 GUIDELINES ON INTELLIGENT PIG TYPE SELECTION

4.1 Corrosion morphology4.2 Fluid type4.3 Pipe geometry4.3.1 Diameter 4.3.2 Curves4.3.3 Pipeline thickness

4.4 Purpose of the inspection4.5 Pipeline location4.6 Extraneous matters in the pipeline4.7 Comparison between the instruments

5 RESULTS OF THE INSPECTION

5.1 Results5.2 Interpretation of results


4/28



6 CRITERIA FOR INTELLIGENT PIG INSPECTION

6.1 Probabilistic approach to intelligent pig inspections6.2 Pipeline integrity assessment6.2.1 Evaluation parameters6.2.2 Criteria

6.3 Monitoring of corrosion - New pipelines6.3.1 Evaluation parameters6.3.2 Criteria

6.4 Monitoring of corrosion. In-service pipelines

7 GUIDELINES FOR THE VERIFICATION OF INSPECTIONFEASIBILITY

7.1 Verification criteria

8 DOCUMENTATION


5/28



1 GENERAL

1.1 Scope

This document provides criteria for intelligent pig inspections of carbon and lowalloy steel pipelines for liquid and gas hydrocarbons, with particular attention tothe aspects related to corrosion, internal and external.

In this document, as intelligent pig is intended a device of any kind able to movefreely inside a pipeline pushed by the transported fluid, suitable to execute

measurements of thickness loss due to corrosion and to detect existing defects of the pipe. This document does not cover the so called cable-operated intelligent pigs or, in general, other methods for the internal inspection of pipelines.

The aims of this document are the followings: to identify the scope of the inspection; to illustrate the features of various types of available devices and their

advantages and drawbacks; to provide guidelines to select the type of instrument related with the scope of

the inspection; to provide guidelines for the planning of inspections with intelligent pigs.

Furthermore, requirements for the inspectionability of pipelines are mentioned.


6/28



1.2 Normative references

1.2.1 European normative references

No European normative references exist on the argument of this specification.

1.2.2 Normative references of ISO, IEC and national organizations

ISO 8044 Corrosion of Metals and Alloys - Vocabulary

1.2.3 Normative references of other organizations

ASME B31G Manual for Determining the Remaining Strength of Corroded Pipelines

ASME B31.4 Pipeline Transportation Systems for LiquidHydrocarbons and Other Liquids

ASME B31.8 Gas Transmission and Distribution Piping Systems

EFC N 16 Guidelines on Material Requirements for Carbon andLow Alloy Steels for H 2S Containing Oil andGasfield Service. The Institute of Materials

NACE MR0175 Sulphide Stress Cracking Resistant MetallicMaterials for Oilfield Equipment

NACE RP0175 Control of Internal Corrosion in Steel Pipelines andPiping Systems

NACE RP0775 Preparation and Installation of Corrosion Couponsand Interpretation of Test Data in Oil ProductionPractice

1.2.4 Internal normative references

06806.PLI.MEC.SPC. Modalit di esecuzione del Pigging di condotteon-shore

06805.SLI.OFF.SPC. Modalit di esecuzione del Pigging di condotteoffshore

02555.VAR.COR.PRG. Internal Corrosion. Corrosion Parameters andClassification of the Fluids


7/28


8/28



Hydrogen Induced Cracking - HIC

A type of stepwise cracking in steel for pipes or laminated products; cracks onthe same plane have the tendency to join with cracks in near levels forming stepsthrough the metallic wall, reducing its mechanical resistance(02555.VAR.COR.PRG).

InspectionA process carried out through measurements, controls, tests or other methods fitto determine the state or the conditions of a pipe with respect to prescribedstandards.

Pipeline integrityThe condition of a pipeline, with respect to its capability of containing andtransporting the fluid, defined in terms of full functionality.

Intelligent pigA pig able to notice existing defects of the pipe due to corrosion throughmeasurements of thickness.

Maximum Operating Pressure (MOP)It is the maximum operating pressure at which a pipe, or a part of it, can beoperated.

PigA device able to move freely inside a pipe pushed by the fluid it transports.

Pitting CorrosionCorrosion resulting in pits, i.e. cavities extending from the surface into the metal(ISO 8044).

Predicted corrosion rateIt is the corrosion rate, usually expressed quantitatively (in mm/y) and/or qualitatively (with an assessment), determined: (a) after the corrosion study,applying all the available knowledge and tools; (b) through laboratory tests,simulating the real conditions; (c) on the basis of field corrosion monitoring dataapplicable to the case under study (02555.VAR.COR.PRG).

Sour conditionsConditions, usually with H 2S presence, that cause Sulphide Stress Crackingoccurrence in susceptible materials (NACE MR0175).


9/28



Stress Corrosion Cracking - SCC

A process resulting form the combined action of corrosion and tension mechanicalsolicitation due to residual or applied stresses; it causes the formation of surfacestress corrosion cracks; cracks are usually perpendicular to stress direction(02555.VAR.COR.PRG).

Sulphide Stress Cracking - SSCFormation of cracks caused by stress corrosion, with a significant contribution of H2S as a corroding agent (02555.VAR.COR.PRG).

Type of fluidIn the present document the following types of fluid are considered: liquidhydrocarbons (I.L.); gas hydrocarbons and gas with condensates (I.G.).


10/28



2 PURPOSES OF INTELLIGENT PIG INSPECTION

The inspection of a pipeline with an intelligent pig usually has one of the following purposes: to assess the integrity of the pipeline; to monitor the internal and external corrosion conditions of the pipeline.

The selection of the most suitable type of intelligent pig and the decision criteria to perform the inspection are also related with intelligent pig inspection purpose.

2.1 Pipeline integrity assessment

The inspection with intelligent pig of pipelines for integrity assessment is performed to check that there are no defects able to compromise its correctservice. It may be carried out at any time during the operating life and repeated

periodically.

The inspection with intelligent pig for integrity assessment finds its most significantapplication with in-service pipeline. In comparison with the traditional hydraulictest, the inspection with intelligent pig offers the following advantages:

interruption of production is not required;

information are provided about the seriousness of the defects. The hydraulic testdoes not give information about the level of pipe defectiveness; moreover, evenif the result of the test is positive, the test itself could have induced a sub-criticalgrowth of existing defects;

it locates the position of the defects.

The following steps are foreseen for the pipeline integrity assessment: inspection with intelligent pig for existing defects survey; elaboration of the results in order to evaluate their acceptability.

The elaboration of the results, that is beyond the scopes of this document, may be

conducted, for example, in accordance with the ASME B31G standard. It assessesthe seriousness of the defects in relation to their depth, length and to the MaximumOperating Pressure (MOP) of the pipeline.

On the basis of the results of the inspection and their subsequent elaboration, it is possible, for example, to recalculate the MOP and, if necessary, to downgrade the pipeline.


11/28



2.2 Corrosion monitoring

In the present document, corrosion monitoring is intended as the intelligent piginspection of a pipeline in order to estimate the average corrosion rate.

The most significant application of corrosion monitoring with intelligent piginspection regards the case of new pipelines transporting a corrosive fluid, in order to assess, in the early operating steps, that the methods adopted to mitigatecorrosion are really suitable.

The corrosion monitoring with intelligent pig requires at least two subsequentinspections:

a first inspection, to be performed just after the pipe has been laid, or during theearly operating phases, establishes the reference inspection;

subsequent inspections, conducted after a period of time variable from case tocase, usually not less than one year, allow, by means of a comparison with thereference inspection, to determine the average corrosion rate in the positionswhere defects have been found.

The monitoring of corrosion requires instruments able to detect small thicknesslosses due to corrosion and with a good level of measurements repeatability ( 0.5mm for the measurement of thickness losses) so that it is possible to use the resultsof at least two inspections conducted in different times to evaluate the average rateof corrosion in the period.


12/28


13/28



Magnetic flux pigs are divided in high and low performance pigs. The maindifferentiating factor is the ability of high performance magnetic flux pigs todistinguish between external and internal defects. In order to do this, probes for thedetection of internal defects employ the eddy current technology or Hall effect

probes. The latter, by measuring the absolute value of magnetic fields (while thetraditional method measures the flux gradient), allow also the measurement of theaverage residual thickness.

Magnetic flux pigs may be used without distinction for pipelines transporting oil or gas.

Generally, they detect localised corrosion attacks better than uniform ones.

Magnetic flux pigs have a low ability to detect, and to correctly evaluate thedimensions of defects situated by or near (up to a few centimetres) girth welds andcurves.

They are presently available for pipes with a diameter greater or equal to 6 (152mm) and are compatible with curves whose minimum radius is 3 times the externaldiameter of the pipe.

3.3 Ultrasonic Pigs

Ultrasonic pigs are instruments equipped with ultrasonic transducers positioned ata fixed distance from the wall of the pipe. The transducers emit sonic impulses

perpendicular to the pipe walls that are reflected partially by the inner wall and partially by the external wall. The measurement of the time interval between thetwo sound echoes allows to go back directly, with good repeatability and highreliability, to the measure of the thickness. However, the two echoes cannot bedistinguished if the residual thickness is too small or the thickness of the pipe is lessthan a limit value. Actually with these devices it is possible to inspect pipes with athickness greater than 4 mm and smaller than 50 mm.

Ultrasonic pigs need, in order to work, the presence of a liquid phase between thetransducers and the wall of the pipe. With regard to this it should be noticed thatthe presence of deposits (for example paraffin) hinders the acquisition of readings.This imposes that:

in case of pipelines transporting gas, the pigs has to be launched inside a liquidslug;

before conducting an inspection an accurate cleaning of the pipeline has to becarried out.

Presently, they offer the chance to evaluate, besides conventional defects likethickness losses, also internal defects of the material like lamination cracks,

provided they exceed a minimum dimension (20 mm).


14/28



Devices are available on the market for pipelines with a diameter greater or equalto 6 (152 mm), compatible with curves whose minimum radius is 3 times theexternal diameter of the pipe.

3.4 Eddy Current Pigs

Eddy current pigs are based on the measurement of the current induced in the wallsof the pipe by a magnetic field, varying in time according to a sinusoidal law,

produced by suitable magnetisation circuits mounted on the pig itself.

The small dimension of these devices allows to inspect pipes with a diameter of 3(76 mm) and with curves up to 95, with a radius of curvature equal to 1.5 timesthe external diameter of the pipe. Nevertheless these devices may be used only witha pipe thickness between 3.2 and 7.1 mm, and are able to give only an absolutemeasurement of residual thickness, with no distinction between external andinternal corrosion.


15/28



4 GUIDELINES ON INTELLIGENT PIG TYPE SELECTION

The selection of the optimal method for the inspection of a pipe is based on thecomparison between the performances of the devices (feature and limitations) andthe requirements of the inspection in connection with functional, security andeconomic factors. The most important aspects to be considered are:

the expected corrosion morphology; the fluid type; the pipe geometry; the purpose of the inspection; the location of the pipe; the presence of extraneous matter within the pipe.

4.1 Corrosion morphology

Corrosion forms may be divided into the following fundamental types, according tothe attack morphology:

General corrosion: it occurs on the whole surface of the metal in contact with theenvironment; it can be uniform, with a generalised and regular loss of metal on theexposed surface, or non uniform, with corrosion penetration varying from area to

area.

The following classes may be used to express the penetration rate of generalcorrosion forms (internal normative reference 02555.VAR.COR.PRG):

negligible: < 50 m/y low: < 50 100 m/y moderate: 100 500 m/y severe: 500 1000 m/y very severe: > 1000 m/y

This classification, applicable to evaluate the corrosion rate expected during thedesign or observed on operating structures, is different from the one proposed by

NACE RP0775. The latter, more conservative, is oriented at the evaluation of corrosion as measured by monitoring systems, particularly by weight loss coupons.

Localised corrosion: it occurs on a limited portion of surface exposed to theenvironment. The morphology of localised corrosion changes considerably,depending on material and environment. The entity of damage does not depend onthe total quantity of oxidised metal.

Ultrasonic pigs are suitable to detect general corrosion attacks. Magnetic flux pigs,on the contrary, are more sensitive to localised defects.


16/28



Eddy current pigs provide the measurement of residual thickness, with no

distinction between external and internal corrosion, and are suitable to detectgeneral corrosion.

4.2 Fluid type

Ultrasonic pigs need the presence of a liquid phase to allow an adequate contact between the probe and the metallic wall. Therefore, the launch of pigs into pipelines transporting gas or multiphase systems has to be conducted within aliquid slug.

If water is employed as circulation liquid for the pig, possible corrosive effects of the water shall be adequately prevented, for example by treating it with corrosioninhibitors or by having the inspection followed by circulation of a slug of corrosioninhibitor.

In case of H 2S containing fluids (sour conditions), all metallic components of the pig shall comply with the requirements of NACE MR0175.

4.3 Pipe geometry

The pipeline geometry shall be carefully considered in order to avoid block risk of the intelligent pig inside.

The most important parameter to be taken into account are: the diameter and its internal variations; curves, with special regard to their angular width and radius of curvature; the pipe wall thickness.

4.3.1 Diameter

Pipelines with a diameter between 3 (76 mm) and 6 (152 mm) can be inspected

only with eddy current pigs.Pipelines with a diameter greater than 6 (152 mm) can be inspected with everytype of intelligent pigs.

The uniformity of the pipelines internal diameter shall be carefully considered.Another important factor are the discontinuities in correspondence of welds.

The Contractor shall verify, in each occasion, the feasibility of the inspection inconnection with the extent and the type of restrictions existing along the pipeline.


17/28



4.3.2 Curves

Generally it is possible to inspect pipelines whose curves have a radius greater than 3 times the external diameter and angular width smaller than 90.

For pipelines with curves of a smaller radius, the inspection can be conducted withsuitably modified devices. The Contractor shall verify, in this cases, the feasibilityof the inspection..

4.3.3 Pipeline thickness

Selection among various types of available intelligent pigs depends on the wall

thickness of the pipeline to inspect.

It is possible to employ eddy current pigs with pipelines whose thickness is between 3.2 and 7.1 mm.

It is possible to employ magnetic flux pigs with pipelines whose thickness is belowa limit value, depending on the pipe diameter. Generally, with diameters greater than 16 (400 mm) the limit thickness of the pipe is 20 mm; with diameter smaller than 16 (400 mm) it is calculated with the following relationship:

Th_max = D/20

where:Th_max: maximum inspectionable thickness with a magnetic flux pig, in mmD: nominal diameter of the pipe, in mm

It is possible to employ ultrasonic pigs with pipes whose thickness is between 4and 50 mm.

4.4 Purpose of the inspection

Depending on the specific purpose of the inspection, different requirements for theinspection tool are needed with respect to the quality of the readings. Particularly,for pipeline integrity assessment, tools shall be employed suitable to detect alldefects with a depth greater than a minimum threshold (as defined for instance byASME B31G); therefore fairly sensitive and accurate measuring devices arerequired; on the contrary, to monitor corrosion it is necessary to detect allthickness losses with accuracy.

Tools based on deviated magnetic flux method are better suited to answer therequisites of pipeline integrity assessment, while ultrasonic tools are recommended,in addition to integrity assessment, also for corrosion monitoring.


18/28



In case of corrosion monitoring, inspections subsequent to the first shall be carried

out using the same type of device employed in the first one.

4.5 Pipeline location

High precision and sensitivity are recommended for the inspection of sealines. For buried pipelines, the selection of the inspection method is primarily based oneconomic criteria and therefore the preferred options are those one that minimisethe inspection costs and the subsequent verification through sample excavations.

4.6 Extraneous matters in the pipelineExtraneous matters in the pipeline to inspect may block the passage of the pig,

piling up in front of the tool itself, and cause reading problems. Their removal istherefore one of the most important operations for the preparation of theinspection.

Extraneous materials may include: steel objects and scrap: for example welding electrodes; gross fragments; fine particles: for example sand; paraffins; corrosion products; scales.

The accuracy level required for the cleaning of the pipe also depends on the type of tool.

Removal of steel scrap, performed in the preliminary phase of the inspection usingmagnetic cleaning pigs, is especially important for magnetic flux and eddy current

pigs.

Ultrasonic pigs require a more accurate cleaning, in particular the removal of deposits, to allow the direct contact between the pipe wall and the measuring probes.


19/28



4.7 Comparison between the instruments

Table 1 shows the most relevant features of the tools considered in this document.

Tab. 1 - Comparison between the instruments

Type of Pig

Parameter

low performancemagnetic flux

high performancemagnetic flux

ultrasounds eddy current

Purpose of theinspection

integrityassessment

integrityassessment

(monitoring)

monitoring(integrity

assessment)

integrityassessment

Corrosionmorphology

general localised (general) general(localised)

general

Defects detection internal internal/external internal/external (residualthickness)

Fluid type all all all 1 all

Max. temperature 50 C 50 C 50 C 40 C

Min. temperature z 4 C 4 C 4 C

Max. pressure 150 bar 150 bar 120 bar 50 bar Min. diameter 152 mm (6) 152 mm (6) 152 mm (6) 76 mm (3)

Max. thickness 20 mm

D/Th > 20

20 mm

D/Th > 20

min. 4 mm

max. 40 mm

min. 3.2 mm

max. 7.1 mm

Recommendedspeed

1 m/s 1 m/s 1 m/s 0.25 m/s

Minimum speed 0.3 m/s 0.3 m/s 0.8 m/s

Maximum speed 3 m/s 3 m/s 2 m/s

Min. curvatureradius

3 D 3 D 3 D 1.5 D

Max. curve angle 90 90 90 95

Required cleaning medium medium high medium

Type of measurement

intrusive

indirect

intrusive

indirect

intrusive

direct

intrusive

indirect1 The launch of a liquid slug is required in the case of gas

Legend: D = External diameter Th = Thickness


20/28



5 RESULTS OF THE INSPECTION

5.1 Results

The Contractor is responsible to issue the data collected in the inspection in theform of a file stored on a magnetic computer support (floppy disk or equivalent).

The Contractor is also responsible for the supplying of a document that gathers andhighlights:

all data regarding the inspection;

all detected anomalies; the distinction between the signals related to normal features of the pipe or itsfittings (welds, joints, flanges, valves) and the ones related to corrosion defectsdetected in the inspection;

the statistical distribution of corrosion defects with respect to their depth; the statistical distribution of corrosion defects with respect to their length; the statistical distribution of the number of corrosion defects for linear kilometre

of pipe; the interpretation of results with the information of the confidence intervals for

the results obtained.


21/28



5.2 Interpretation of results

The interpretation of results is performed by the Contractor, using appropriate data processing software.

Defects shall be ordered according to their depth relatively to the thickness of the pipe.

The classification is made by grouping together the defects for depth intervals.Usually a number of four damage classes are considered, whose limits are definedcase by case, according to the depth distribution of detected defects. An exampleof definition of damage classes follows:

class qualitative damageevaluation

thickness reductionpercentage

1 low < 20

2 moderate 20 - 40

3 severe 40 -60

4 very severe > 60

In any case, the Customer reserves the right to ask further or differentclassifications.

Data regarding subsequent inspections of the same pipeline shall be properly filedwith easy accessibility.


22/28


23/28



6.2 Pipeline integrity assessment

The decision to perform the inspection may be taken at any moment of theoperating life of the pipeline and does not require a comparison with previousinspections.

As already mentioned, it covers its most significant application with pipelineswhose age is close to their design life.

6.2.1 Evaluation parameters

The decision to conduct the inspection requires the acquisition of the followingdata.

6.2.1.1 Pipeline data

They include: pipeline age; residual life; features of the pipeline material: chemical composition; mechanical properties; welding procedures; non destructive tests results; compliance with references normative and with design data; corrosion mitigation methods.

The historical review of the operating phases of the pipeline shall be conducted,with particular attention to:

evolution of operative parameters (temperature and pressure); changes intervened in the flow rates; changes intervened in the fluid composition, particularly in the water phase flow

rate and in the chemical composition (CO 2 and H 2S molar fractions in the gas phase, chemical composition of the water phase);

corrosion events occurred; possible pipe inactivity periods and measures adopted to control corrosion.

6.2.1.2 Data regarding internal corrosion

These data include: transported fluids and their chemical composition, particularly for the water

phase; fluidodynamic conditions: prevailing flow patterns; phases flow rates; internal corrosion monitoring data.


24/28



6.2.1.3 Data regarding external corrosion

These data include: environment corrosivity - soil or sea water; monitoring data of the cathode protection system; monitoring data of coating conditions.

The evaluation of corrosion probability for pipelines in contact with soil or seawater shall be carried out following specific studies.

6.2.1.4 Context and economic data

Data concerning the context are used in the evaluation of the entity of consequences in case of leakage.

Consequences include: the costs for the repair of the failure; the loss of production; other possible

indirect damages; social costs: damages to individuals; damages to the environment.

Other important parameters are: the location of the pipeline: onshore or offshore; for onshore pipelines, the population density in the surrounding area; the features of the fluids, in connection with risk for people and environment; the times and costs of repair in case of failure; the flow rates and the unitary value of production.

6.2.2 Criteria

Some of the main aspects to consider when trying to identify the priorities of inspection operations are reported, as guidelines, here below.

Pipelines operating from more than 10 years; they are in conditions in whichcorrosion defects, that grow continuously in time, could reach criticaldimensions.

Offshore pipelines. The costs for offshore repair operation are usually very high. Pipelines for the transportation of corrosive or untreated fluids. Offshore pipelines located near risk areas for the environment or the population. Large size pipelines with significant flow rates.


25/28



6.3 Monitoring of corrosion - New pipelines

The inspection with intelligent pig for the monitoring of corrosion is based on thecomparison between two subsequent inspections; its most significant employmentis with new pipelines, in order to verify the adequacy of the adopted internalcorrosion control systems.

The inspection for the monitoring is therefore identified by: the decision to perform the first inspection, i.e. the blank; the frequency of subsequent inspections.

6.3.1 Evaluation parameters

Evaluation parameters are the same reported for the integrity control.

The analysis is targeted at aspects concerning internal corrosion, while usuallyexternal corrosion has no a significant role in the decision about performing theinspection.

6.3.2 Criteria

For new pipelines, the execution of a preliminary inspection at the beginning of operations shall be evaluated during the design phase of the pipeline.

The execution of a preliminary inspection is recommended in the following cases: Offshore pipelines for transportation of untreated fluids - non stabilised oil; wet

gas; multiphase systems - from platform to treatment plant, every time theinternal corrosivity is expected to be severe or very severe.

Onshore pipelines for transportation of untreated fluids - non stabilised oil; wetgas or multiphase systems from production wells - to treatment plant, operatingin contact with fluids whose corrosivity is severe or very severe or with a highcorrosion probability and located near risk areas for the environment or the

population.

Subsequent inspections shall be performed after a period of 1 to 5 years, inconnection with the features of the pipe and the corrosivity of the fluids.


26/28



6.4 Monitoring of corrosion. In-service pipelines

The inspection with intelligent pig for the monitoring of corrosion may be usedalso on in-service pipelines to accomplish more tasks at once:

to verify the pipeline integrity; to evaluate the effectiveness of internal corrosion mitigation systems, specially

after changes in the composition of the fluids, particularly changes in water flowrate, and in the chemical compositions (CO 2 and H 2S molar fractions in the gas

phase, chemical composition of the water phase); to monitor the corrosion status of the pipeline, following the detection of

pipeline defects, in order to gather data that allow predictions about theevolution of the defects and to plan the possible repair operations.

As in the previous case, the inspection for corrosion monitoring is identified by: the decision to perform the first inspection, as reference, that allows to obtain

also data for the evaluation of the pipeline integrity; the frequency of subsequent inspections.

As regards evaluation parameters and criteria, refer to Chapters 6.2 and 6.3.


27/28


28/28


8 DOCUMENTATION

As for the results of the inspection are concerned, the Contractor shall provide thefollowing documentation:

file of measurement data as shown in Chapter 5.1; printout of the results as shown in Chapter 5.1.

agip - std transport and gathering pipelines inspections with intelligent pig

Documents