rehabilitation of a pipeline in a new european country

7/27/2019 Rehabilitation of a pipeline in a new European country

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5 PiPelines international digest | deCeMBer 2011

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T

he management wanted to know the actual integrity status

of the pipelines and information regarding other details of

the lines (such as their exact route). Among other factors, the

study involved: Topography survey

Terrestrial survey

Pipeline detection

Geographical investigation for soil-resistivity assessment

Collecting and review of existing information

Collecting right-of-way information at the local city hall and

cadastral data for reimbursement contracts to be made by the

client

Pipeline inspection and integrity non-destructive testing

measurements

Production and delivery of alignment sheets.

The goal of the project was to gather integrity data on these

pipelines and to evaluate these data to determine the integrity

condition of the pipelines and facilities. The pipelines, constructed to

API 5L X52 with bitumen wrapping, were designed in the early 1970s.The pipelines were initially installed with

20 inch diameter pipe, but since 1986 some sections have been

replaced with 16 inch diameter pipe, due to leakage or other

circumstances.

Alternative scope of workAfter a few meetings and an ILF presentation of an alternative

project and survey plan, the client decided to reduce the scope of

work to some basic investigations in order to obtain a rst integrity

status of the pipelines. The survey work would therefore include a

topographic survey, a pipeline-detection survey, a terrestrial survey, a

long-range ultrasonic/guided-wave ultrasonic (LRUT/GWUT) survey,excavations, radiographic inspection (x-ray), and visual inspection.

Topographic surveyThis measured all topographical items, including landmarks,

buildings, streams, rivers, rail tracks, roads, visible crossings of

third-party infrastructure, etc., in a 50 m corridor on both sides of the

pipeline. The data collected were entered onto alignment sheets and

delivered as a database, conforming to the geographical information

system (GIS) database structure prescribed by the client, for direct

implementation into the GIS.

Pipeline detection survey

This was needed to gather the necessary data to develop detailedalignment sheets and to prepare reliable as-build documentation.

This survey recorded the exact pipeline position (x, y, z), bend

identication, and possible diameter changes.

Terrestrial surveyAll structures and landmarks, in corridor of 100 m on both sides

of the pipeline, were surveyed to gather reliable data on terrestrial

conditions and to mark the pipeline route with a grid of survey

reference markers for possible rehabilitation project execution on the

pipelines.

LRUT/GWUTThe most suitable positions for LRUT/GWUT were determined,

together with the client; these were at locations were the pipeline

route changes from above-ground to below-ground. With these

Rehabilitation of a pipeline

in a new European countryby Abraham Louwerse, ILF Consulting Engineers, Munich, GermanyILF was invited to assess the integrity status of two pipelines in a new European country. In the last few years there were someleakages and nobody really knew the exact position of these pipelines and equipment. The pipelines were installed 30 yearsago, and there was little documentation available; the pipelines are non-piggable and are without any cathodic protection.The client decided to carry out an integrity-assessment study for these two major pipelines before deciding on rehabilitationprocedures.

Figure 1: The LRUT/GWUT system in use.
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spot checks, at the most corrosion-sensitive area of the pipelines, it

was possible to evaluate the general integrity of the pipeline.

The advanced LRUT/GWUT system (Figure 1) is designed for rapid

screening of long lengths of pipe to detect corrosion and other

forms of axial and circumferential metal degradation. It can be

used on a wide variety of pipes including those that are insulated.

The tests can be done with the pipeline operational (inservice), sodisruption and any expensive down-time are minimised. Hundreds

of metres of pipe can be inspected in a single shift and 100 per cent

thickness of the pipe wall is inspected during a test.

The LRUT/GWUT system uses low-frequency ultrasonic guided-

waves that travel along the full wall thickness of the pipe as a

circular type wave front around the pipe circumference. The

pulse-echo application means that changes in wall thickness

(such as corrosion) along the pipe length will generate signals that

return to the transducers. These returning echoes are presented

on a simple amplitude versus distance A-scan signal, which theoperator can use to discriminate between genuine pipe features

(such as welds) and problem areas (such as corrosion wall loss)

via the operational software.

Figure 2: EMAT schematic.

Chainage No.Diameter

(inches)

Wall

thickness

(mm)

Defects

144 IP3A 20 8.34 Coating degradation and damage

5054 IP22 24 11.9 OK

11628 IP34 16 9.36Coating degradation, dent in pipeline, welding anomalies

Bad support with corrosion indication

18081 IP36C 16 9.2Coating degradation and damage, welding anomalies


24417 IP37 16 8.39 Coating degradation and damage

31418 IP58 16 7.75 Crossing is sagging, welding anomalies

31681 IP60 14 12.2 Coating degradation and damage, four anomalies detected

32315 IP61A 16 7.75 Coating degradation and damage, two welding anomalies

32794 IP61B 16 7.95Coating degradation and damage, welding anomalies



47534 IP77A 16 7.92 Coating degradation and damage

53144 IP85 20 14.38Coating degradation and damage, two remnant welding

anomalies, Bow crossing of ditch



62100 IP95C 20 7.92 Coating degradation and damage

85213 IP120 20 7.83 Coating degradation and damage, four anomalies detected(Class 2, 3), four welding anomalies

100026 IP139 16 9.35Coating degradation and damage, four anomalies detected

(Class 2, 3), nine welding anomalies

Table 1: LRUT and GWUT investigations or the Route 1 pipeline.
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Chainage No.Diameter

(inches)

Wall

thickness

(mm)

Defects

13 MS2 8 7.89 Coating degradation and damage

94 MS4 14 8.63 OK


643 MS7A 16 7.16Three leak repairs and coating with severe degradation

672 MS7B 16 6.9

3420 MS14 16 10.5 OK


6318 MS24 16 12.33 Defects in welding

22271 MS47 16 7.6 OK

26757 MS54 16 8.63 Welding defects

Table 2: LRUT and GWUT investigations or the Route 2 pipeline.

Chainage Depth (m)Diameter

(inches)Pipe type Condition Radius (m) Angle ()

3,160 m 120 cm 16 Spiral 2.6 124

3,407 m 150 cm 16 3.0 127

3,439 m 130 cm 16 Seamless 1.5 148

8,976 m 130 cm 16 3.0 127

9,319 m 100 cm 16 7.0 114

18,655 m 120 cm 16 Spiral Corrosion 6.4 140

22,207 m 120 cm 16 Spiral Corrosion 5.0 134

Table 4: Pipe bends (elbows) and diameter or the Route 2 pipeline.

Chainage Depth (m) Diameter(inches)

Pipe type Condition Radius (m) Angle ()

6,375 m 150 20 Seamless 1.5 159

7,648 m 130 20 Seamless 1.5 147

32,489 m 150 20 Seamless Poor 0.6 90

32,792 m 190 20 Seamless Bad 0.7 110

33,664 m 60 20 Segments 116

55,569 m 95 20 Spiral Bad 4.6 138

62,725 m 130 20 Seamless Poor 0.8 112

63,425 m 150 16 Seamless Good 0.9 120

75,231 m 200 20 6 9091,747 m 160 20 6.5 140

Table 3: Pipe bends (elbows) and diameter or the Route 1 pipeline.
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Two types of guided wave longitudinal and torsional are

used to broaden the range of possible frequencies and to adjust

for dierent situations, for example the presence of liquids.

Symmetrical and exural waves allow defect detection and

interpretation of the results.

An important point to note is that LRUT/GWUT techniques do

not provide a direct measurement of pipe wall thickness, but

are sensitive to a combination of the depth and circumferential

extent of any metal loss. LRUT/GWUT is not able to distinguish

the dierence between internal or external material loss.

As a redundancy for the LRUT/GWUT we executed nineEMAT measurements on positions where the spiral-welded

pipe was giving bad readings via the LRUT/GWUT technology.

In this case, the electromagnetic acoustic transducer (EMAT)

technology was a hand-held tool which could be moved around

the pipe (it was not a collar, like guided wave). The EMAT must

be placed on the pipe and it shoots forwards by approximately

1.5 m (Figure 2). The transducer can be moved circumferentially

around the pipe and with this movement a 360 coverage with a

measuring length of

1.5 m can be achieved.

ExcavationsFifty locations were selected to excavate the pipeline for the

bend identication and wall thickness measurements. Thediameter changes should have been excavated as well, but

because of the method used for pipeline replacement in the

past, these were not detectable.

Table 5: Wall thickness measurement or the Route 1 pipeline.

ChainagePipeline

depth (cm)Pipe type Grade

Pipe

condition

Pipe

diameter

(inches)

Wall

thickness

min (mm)

Wall

thickness

max (mm)

144 m API 5L X52 20 7.8 8.1

5,054 m Spiral API 5L X52 Bad 20 9.5 12.5

5,141 m AG API 5L X52 20 9.2 9.2

6,375 m 150 Seamless API 5L X52 20 12.9 13.6

7,648 m 130 Seamless API 5L X52 20 8.18 13.8

11,628 m AG Spiral API 5L X52 Bad 16 8.5 9.6

Spiral API 5L X52 Poor 8.7 8.7

Spiral API 5L X52 Poor 8.7 8.7

24,417 m AG Spiral API 5L X52 20 8.0 8.9

2628 km 130 Spiral API 5L X52 Bad 20 3.6 7.9

29,621 m AG Seamless API 5L X52 Poor 22 9.4 9.8

30,127 m AG Seamless Poor 20 7.7 7.8

31,418 m AG Spiral API 5L X52 Poor 20 7.5 7.931,604 m AG Seamless Poor 14 12.2 12.9

32,315 m AG Spiral Poor 14 7.2 8.8

32,465 m AG Spiral Poor 14 7.2 8.8

32,489 m 150 Seamless API 5L X52 Poor 20 7.5 9.8

32,792 m 190 Seamless API 5L X52 Bad 20 9.6 10.9

33,664 m 60 20 7.9 8.2

36,144 m AG Spiral API 5L X52 20 7.0 7.2

Spiral API 5L X52 Poor 20 6.9 7.5

53,144 m AG Seamless Poor 20 13.0 15.1

54,231 m AG Spiral API 5L X52 Poor 20 8.6 9.255,569 m 95 Spiral API 5L X52 Bad 20 7.9 11.9

55,726 m API 5L X52 Bad 20 7.8 9.1

Spiral API 5L X52 Poor 20 7.0 7.9

62,725 m 130 Seamless Poor 20 9.3 9.3

63,425 m 150 Seamless Good 20 9.4 10.8

75,231 m 200 20 8.3 9.3


91,747 m 160 API 5L X52 20 9 9.4

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According to the information received from the client, the

bypasses should have been constructed in parallel positions to the

old pipeline, and connected with elbows to the original line. It was

later discovered that this was not the way these bypasses had been

constructed.

After a second detection survey, in which these connections were

still undetectable, the client mobilised its eld inspectors and the

construction company who carried out the bypass construction

to indicate the positions in the eld. During this identicationsurvey we were informed about the changed construction method

for the bypass connections: over a length of 50100 m the new

pipeline was positioned in the original route of the old pipeline and

connected without the elbows as indicated during the project scope.

Due to some landowner issues and high water conditions, there

were some locations which could not be accessed, and at which

excavations were therefore cancelled by the clients project

management and ILF. At the other excavations, the pipeline

diameter and wall thickness were measured and a general

inspection of the coating was performed.

Bends (elbows)In agreement with the client, the locations of short-radius bends

and elbows which were excavated during the pipeline-detection

survey to investigate the bend type, radius, change of direction

angle, wall thickness, position, depth, and coating condition

were selected. Table 3 shows the data from these investigations.

According to EN 1594, eld bends for pipelines greater than 16

inches in diameter shall have at least 40 times the diameter: this is

a radius of 16 m for 16 inches, and 20.3 m for 20 inch pipes. Factory

bends can have smaller radii. In general bends, made of segments

(mitred, or cut elbows) are not permitted according to EN 14161.

While only performing visual inspection on the investigated

bends, it was not possible to identify if the bends were mitred orfactory bends.

Wall thicknessAccording to EN 1594 the minimum required wall thickness is

calculated with following equation:

where:

DP = design pressure (bar)

DOD = outside diameter (mm)

fo = utilisation factor according to EN 1594Rt0.5 = yield strength according to API 5L (N/mm)

This equation does not consider any supplemental wall

thickness, such as might be used for corrosion. Also, the equation

Table 6: Wall thickness measurement or the Route 2 pipeline.

Table 7: Clients technical specifcation or wall thickness.

ChainagePipeline

depth (cm)Pipe type Grade

Pipe

condition

Pipe

diameter

(inches)

Wall

thickness

min (mm)

Wall

thickness

max (mm)

013 m AG Seamless API 5L X52 Fair 814 7.7 8.0

94 m 90 Seamless API 5L X52 Bad 16 8.2 8.9

466 m AG Spiral API 5L X52 Corrosion 16 6.9 7.3

657 m 80 Spiral API 5L X52 Corrosion 16 7.0 7.3

3,160 m 120 Spiral API 5L X52 16 10.0 10.8

3,407 m 150 API 5L X52 16 6.3 6.8

3,411 m AG Spiral API 5L X52 Corrosion 16 7.2 10.8

3,439 m 130 Seamless API 5L X52 16 10.9 11.8


Spiral API 5L X52 Corrosion 16 11.5 13.5

8,976 m 130 API 5L X52 16 6.3 6.8

9,319 m 100 API 5L X52 16 9.9 10.6

18,655 m 120 Spiral API 5L X52 Corrosion 16 10.0 10.022,207 m 120 Spiral API 5L X52 Corrosion 16 9.3 10.1

22,227 m 120 Spiral API 5L X52 Corrosion 16 7.5 7.6


Pipe diameter

(inches)

Design pressure classes

Wall thickness

(mm)

Alternative

wall thickness

(mm)

(client approval

needed)

GradeANSI ISO (bar)

16 400 64 12.5 8.8 L360 NB

20 400 64 14.2 10 L360 NB
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is only a rule of thumb and is valid for straight pipe (not for

bends).

For the Route 1 pipeline with its original operating pressure of

36 bar, an fo of 0.72 (which is the reciprocal safety factor), and Rt0.5

of 360 N/mm, this leads to a minimum wall thickness of 3 mm for

the 16 inch pipeline, and one of 3.9 mm for the 20 inch pipeline.

For the Route 2 pipeline with an original operating pressure of

42 bar, a wall thickness of 3.6 mm is the absolute minimum

required.

To these values a safety design factor of 2 mm and a corrosion

allowance of 3 mm is to be added, giving the following results:

Route 1: wall thickness >8 mm for the 16 inch and 8.9 mm

for the 20 inch pipelines

Route 2: wall thickness >8.6 mm for the 16 inch pipeline.

According to the clients technical specication, based on the

local standard for wall thickness calculations, the specications

in Table 7 are given, included the prescribed 2 mm safety design

factor and the 3 mm corrosion allowance. All wall thicknesses

below the minimum prescribed values are marked in red in

Tables 5 and 6.

Material

The information received from the client stated that there is onlyAPI 5L X52 and L360 linepipe material used for these pipelines.

According to API 5L, the API 5L X52 and the L360 linepipe

materials are equal. The minimum yield strength (Rt0.5) is 360N/

mm and the chemical composition for X52 gives maximum

contents (mass fraction) of 0.26 per cent carbon, 1.4 per cent of

manganese, and 0.03 per cent of phosphorous and sulphur for

welded pipes (in non-sour service).

Radiographic inspection (x-ray)During the ultrasonic testing (UT) of the pipelines, some

very badly welded seams were visually observed, and it was

recommended to the client that they be checked or examined

by radiographic means. Twelve welded joints were therefore

investigated by means of x-ray inspection to gather information

about the general quality of some suspicious welding joints. The

radiographic test where executed on three joints on the 20 inch

line, two joints on the 24 inch line, six joints on the 16 inch line,

and one joint on the 14 inch line.

The nding after evaluation of the discontinuities on the

radiographic lms were that there had been incomplete

Figure 3: Examples o poor welding.

Table 8: Inspected welded joints.

Chainage value No. Measured Positive result Negative result

3411 MS14 1 (joint) on 14 inch Rejected

6318 MS23 1 (joint) on 16 inch Rejected

5054 IP22 1 (joint) on 24 inch Approved

5054 IP22 1 (ws) on 20 inch Approved

11628 IP34 w1 1 (joint) on 16 inch Rejected

11628 IP34 w2 1 (joint) on 16 inch Approved


31604 IP60 1 (joint) on 14 inch Rejected





Results of the 12 investigation points 3 Approved 9 Rejected
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penetration and/or incomplete fusion, and nine of the 12

investigated joints were therefore rejected. Figure 3 ab and

Table 8 give further details.

Visual inspectionFor all above-ground installations, excavations, and

UT investigation sites, a visual inspection was carried out

which included identification of the pipe type (spiral or

longitudinally welded), the identification of bends, and the

measurement of diameter and wall thickness. Also the general

state of the coating was evaluated and recorded.

For above-ground installations such as flanges and

valves, the general state, presence of all bolts and nuts, and

the corrosion condition, were recorded. The presence of

handwheels for the valves were also checked.

Along the pipeline route there are many roads crossings,

some of which have ventilation pipes which indicate an

installed casing. On the locations where there were no

ventilation pipes observed, especially on the national roadsand highways, it was assumed that, according to the old

standard that was in place during the construction of the

original pipeline, the ventilation pipes were corroded, had

disappeared or been stolen for scrap metal collection.

Data on all road crossings was obtained, regardless of road

type minor, secondary, national, or highway. Some casings

made of old oil barrels under a minor road were detected,

as well as some concrete pipes as a kind of casing under a

secondary road. It was assumed that many of these crossings

had not been constructed in conformity with the old standard,

and certainly they were not in accordance with new standards

and practices.

At some water crossings the pipe could be seen lying directly

in the watercourse. According to European norms, the rule for

thumb for water crossings is to cross at least 0.8 m below the

deepest point of the water course.

Instrumentation and pipeline valvesIn general, the inspected instrumentation and valves were in

a very poor condition, and it was not certain whether the valve

diameter matched the pipeline diameter for many valves. None

of the valves could be remotely controlled and, in many cases,

the handwheels to operate the valves were missing. Even if

there was a handwheel, it was very hard or even impossible

to operate due to corrosion. In some cases flange bolts weremissing. Mostly the external conditions were between bad

and poor, and paint had been used for corrosion protection (if

existent at all). At facilities, where identifiable, the pressure

class was PN64.

LeakagesDuring the pipeline detection survey leakages were detected

which were immediately reported to the client. The client had

recorded all leakages on the pipelines in the previous two

years: the total number of reported/recorded leakages in 2008

was 28.

The repair methods were neither in accordance to the qualitycontrol and safety standards of the client nor to internationally

accepted standards (Fig.4 a-c). Most repairs were observed as

being executed by simple steel screwed-on clamps, withoutFigure 4: Examples o poor reinstatement.
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even removing and reinstalling the coating. Some severe

damage caused by excavation works for leakage repair was

also observed on the pipeline.

Buoyancy protectionIn areas where the soil contains a lot of water (moor or

marsh), and also for larger river crossings, buoyancy protection

for the pipeline is required and is mandatory. According to the

European standard EN 1594, the pipe should be ballasted or

anchored, if necessary, in areas where the pipe tends to float or

because of the high groundwater table.

It was seen that some kind of buoyancy protection for the

pipelines had been used in a few locations, although this was

neither according to European standards nor sufficient. At

a few locations the bare pipe was seen lying directly in the

water, covered by some concrete blocks (Figure 5).

Pipeline integrity assessment

Pipelines to be rehabilitated

The pipeline system is a combination of pipelinesconstructed in the 1970s and some new sections that have

been constructed in recent years due to leakages. The newly

constructed pipeline are 16 inch diameter L360 NB with a

three-layer polyethylene (PE) coating; the old, original, 20 inch

diameter pipeline was constructed from API 5L X52 steel with a

bitumen coating.

Because of the bad coating condition of the old pipelines,

frequent leakages, river and road crossings situations, reduced

wall thicknesses, poorly maintained pipeline furniture,

non-classified elbows, non-existing cathodic protection

(CP) system, non-piggability, and bad welding quality, a

rehabilitation was considered for all the old pipelines to thespecification of the newly constructed pipelines to bring this

pipeline system back to fit-for-purpose condition and to be in

line with the standards and pipeline safety regulations.

This meant that there should be rehabilitated 101 km of

new 16 inch pipeline would be installed. The rehabilitation

sequence/steps and detailed explanation are discussed later.

Integrity status conclusions

Integrity managementA pipeline integrity management plan had not been

implemented, and there was no knowledge of the pipelines

integrity. Maintenance had only been carried out in a poor

manner following failure, leakage, or breakdown. The followings

aspects were observed:

Generally, there was no CP system installed; the one that

was partly installed on Route 1 was not maintained.

Wall thickness measurement indicated that, in thelocations that were investigated, +/- 90 per cent, was not

sucient according either the clients standard or the EN

standard.

There was no coating investigation routine, such as direct

current voltage gradient (DCVG).

The lines are not piggable because of:

Elbow and bend radiuses and welds

Gate valves are not full-bore

Diameter reductions

Dierent pipeline diameters

No pig launcher or receiver stations.

Health, safety and environmentThere had been frequent leakages along the pipeline because of

internal and external corrosion, pipe stresses, and geographical

Figure 5: Concrete blocks used at a river crossing.

Figure 6: Concrete block laying on the pipe.
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inuences (such as landslides). This was environmentally

unjustiable and public safety, as well as the safety of the clients

personnel, was in jeopardy. Corporate reputation was also at

stake; when a serious incident occurs, it is realistic to assume

that the pipelines present integrity status will be examined and

published by the public media. As mentioned already, there had

been 28 leakages detected and reported in the last two years.

Pipeline operationWhen looking at the status of the installations and situations

along the pipelines, very strong doubts arose concerning the

qualication and pipeline integrity knowledge of the pipeline

operators. It was strongly suggested that the pipeline operators

and inspectors should be urgently trained in pipeline integrity,

safe operating work procedures, and safety awareness.

For example, an inspectors alarm bells should normally

go o if he observes a heavy concrete block of a few 100 kg

laying on top of the pipeline (Figure 6), or when a pipeline is

completely kinked because of the support of the river crossing

has collapsed (Figure 7).

Steps for rehabilitationThe integrity status of the pipeline had a very low quality, and

the situation was very dangerous for both public safety and the

pipelines direct environment. The asset utilisation and asset

capability were both greatly reduced because of this poor integrity

status, and it was just a matter of time before the pipeline would

have been out of service for a lengthy period because of an

incident.

The following steps for rehabilitation were therefore considered:

Coating integrityChecking the coating of the previous, already constructed

L360 NB pipelines by DCVG and measure the soil resistivity of

the complete pipeline routes.

Design for cathodic protection and isolation couplingsThe CP system must be designed, taking the previous soil

resistivity survey results as base, for an adequate external

corrosion protection. During this design the optimum

and preferable positions for isolation couplings are to be

calculated.

Pipeline exchangeExchange the old API 5L X52 pipeline material with the L360

NB and three-layer PE coating (according to DIN EN ISO 21809).

This means the complete exchange of the 26.766 km Route 2

line and the remaining 74.899 km of 16 inch diameter old Route

1 pipeline. The design of the new pipeline should be piggable

with launcher and receiver stations, and with piggable bends

and valves.

CrossingsAll pipeline crossings should be made by directional drilling,

horizontal directional drilling, or prefabricated siphons; if this

is not possible, existing crossings should be rehabilitated to beof a safe and reliable construction (Figure 8).

Line valves and valve stationsNew 16 inch full-bore line valves should be located in above-

ground stations, and preferably equipped with remote process

control (safety response), and pressure and temperature

transmitters. This means that electrical power supply and

communication, by public network, satellite, or by dedicated

fibre optic cables along the line, will be necessary.

Location of isolation couplings

The requirements for isolation couplings depend on the CPsystem that is to be installed. The exact locations for isolation

couplings cannot be specified until that time.

Figure 8: Pipe bent due to

ground movement.
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Fencing and markersAll above-ground installations should be fenced-in to out keep

unauthorised people and to hinder unauthorised operations.

On the fences, the product identication codes and telephone

numbers should be visible.

All changes in direction and crossings should be identied

with state-of-the-art markers. These markers should have

the clients identication/tag plates on which the emergency

telephone numbers and the position identications are clearly

visible. According to the new standards, the next upstream and

downstream positioned markers should always be able to be

seen, to enable the identication of the pipeline route.

PIMS (pipeline integrity management system)

Pipeline operationsA training programme for pipeline operators and pipeline

inspectors should be set up to make them a part of the PIMS. This

will stimulate a professional dedication to their job and a sense of

responsibility.

It is also important that the operators report their work and

observations to a focal point at their department (the integrity

engineer) in order to gather together all relevant information for

implementation in the new GIS system, and to make it possiblefor the integrity engineers to evaluate the right statistics in order

to initiate maintenance and other relevant actions for integrity

management. The PIMS should include an inspection programme

and a maintenance programme.

Route inspection programmeFor an inspection programme, the following aspects are to be

included:

A time schedule for car, walking, and/or helicopter

inspections.

The pipeline must be clearly indicated by markers.

Templates for inspection reports are to be made. All itemsand installations must be listed, dening how and what is

to be checked and inspected; this includes geographical and

topographical changes.

Figure 9: Unauthorised

excavation o unused section

o line.

Figure 10: The process o managing integrity.
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Procedures are to be set up concerning what is to be

inspected, what is be to reported, how the reports are to be

made, and to whom the reports are to be given.

A schedule for ILI to observe the feature degradation and to

plan maintenance.

Maintenance programmeIn the course of time, several maintenance strategies were

developed with their own advantages and disadvantages. The three

major existing categories of maintenance are:

Corrective maintenance (CM)

Preventive maintenance (PM)

Risk-based maintenance (RBM).

Corrective maintenanceThe CM strategy is independent of time or condition of

the system, and the work consists only of repairing defective

equipment. Thus, the unscheduled and unpredictable work leads

to relatively low costs. High expenditures could arise, however,when the whole system has to be shut down because of the repairs.

Preventive maintenancePM contains all the work/interventions performed periodically

on critical units according to specied instructions, or vendor

maintenance manuals, recommendations, and procedures.

Examples of PM are:

Greasing the valves

Function testing line valves

Emission testing valve seals and compressor/pump seals

Intelligent pig runs

DCVG coating investigation

Close interval potential survey measurements

Cleaning/drying liquids in the pipeline (semi-routine) by

pigging or drain systems.

An extension of preventive maintenance is condition-based

maintenance, which has to be developed for each individual

pipeline system on the basis of the experience during the rst

years of operation, followed by continuous improvement based

on actual experience (the Deming circle).

Risk-based maintenanceIn risk-based maintenance, the system and its components are

evaluated in terms of their probability of failure and the risks

involved (Figure 10). The results are visualised in a risk matrix.

With the focus on the relevant system components for the

operation, the integrity of the whole system is improved. Highly

qualied sta are required to undertake this analysis.

In central Europe, it is recommended that condition-based

maintenance is regularly undertaken to achieve a high reliability

of the individual components and thus for the whole system.

Quantitative risk assessmentBefore commissioning a pipeline a quantitative risk

assessment (Bowtie) should be set up and implemented for

all installations and equipment as well as for the pipeline route

itself. By evaluating the possible internal and external risks it is

possible to direct and customise the operational and integrity-

management system in the high-risk areas along the pipeline,

which include high density population areas, industrial areas,

environmentally sensitive areas, landslide areas, mining areas,

rivers and water crossings, direct current rail tracks, highways,

and parallel crossings with high-voltage power lines.
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rehabilitation of a pipeline in a new european country

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