the introduction of pipeline integrity management by … conferences/2005/sds... · the...

© Gastech 2005

The introduction of pipeline integrity management by

KOGAS By SungBaek Hong, DongGeun Han, YoungGeun Kim. The 21st International Conference & Exhibition for the LNG, and Natural Gas Industries. GAS TECH 2005

Korea Gas Corporation South Korea

© Gastech 2005 Hong 2

Overview Korea gas corporation (KOGAS) operates the total 2451km for natural gas transmission pipeline in Korea. Korea’s

geographic situation is different from the USA, EU country. It has so many high consequences area because it is

geographically very small and limitable, and its population density is very high, compared to the USA and EU country. As

the transmission pipeline is laid along the main road in Korea, the integrity level tends to be one step higher than that of

other countries due to the social reason.

Following diagram is the system of integrity management for KOGAS transmission pipeline.

Integrity management system is composed of periodic monitoring, risk assessment, in-line inspection, defect assessment

and pipeline repair etc.

Fig. 1 the concept of integrity management system

According to KOGAS standard for survey procedure of coating defect, every covered section after completing of

construction should be assessed by coating defect survey, DCVG (Direct Current Voltage Gradient) as a commissioning

procedure. Every coating defect is repaired before the turnover to the operation department. KOGAS established a five-

year reassessment interval for operating pipeline. The reassessment methods are composed of two main indirect survey

methods, DCVG and CIS (close interval survey). The framework of reassessment procedures was activated at the year of

1999. At present, all the pipelines have been surveyed according to the reassessment program that initiated from 1999.

The in-line inspection (ILI) tool survey was started in 1997(in KOGAS). KOGAS had decided to adopt ILI survey as a cyclic

(indirect) inspection method. From 2005, all line segments in operation will be classified into two categories, piggable

Periodic Monitoring

DCVG

CIS, P/S

Corrosion Environment

3rd Party construction

Risk Assessment In-Line Inspection

Gathering and

Integrating Data

Risk factor assessment

Priority management

Determination of

pipeline inspection

method and its

periodicity

Geometry Pig

HR MFL Pig

Pipeline (Coating) repair

Repair procedure

Repair location

(Determination)

Defect Assessment

Excavation

Fitness (Test)

for Purpose


segment and unpiggable segment. Thus So KOGAS has a plan to incorporate a DA (Direct Assessment) procedure into

unpiggable segment which would include DCVG and CIS as major indirect survey technique. This paper describes the

situation and rationale for the pipeline integrity system and management of KOGAS.

Corrosion Control of underground pipelines

The principal methods for mitigating corrosion on underground pipelines are coatings and cathodic protection (CP).

KOGAS also applies impressed current cathodic protection to its underground pipelines.

The rectifiers are used as source of impressed current power. Typical AC input is AC 220/380 V, single /three phase, and

frequency is 60 Hz. Maximum DC output to pipeline negative (-) is 60 V.

KOGAS has defined that it has two type of corrosion control, such as impressed current system, sacrificial Anode system.

In its standard for cathodic protection design of underground pipeline, impressed current system is divided into two types,

one is deep-well anode type, the other is shallow-bed Anode type. KOGAS usually apply deep well anode type to

transmission pipeline and shallow-bed anode type to Gas Supply Station. KOGAS operates 124 deep-well Anode type and

77 Shallow-bed Anode type.

Criteria for Cathodic protection of underground Pipeline or submerged pipeline are following

√ Negative potential of 850mv (Saturated copper-copper sulfate referenced electrode : CSE)

√ Negative potential of 950mv (CSE) is used in the case of microbiologically influenced corrosion (MIC). Survey cycle for

potential of transmission pipeline is every three months.

Coating being used is mostly polyethylene. According to the specification for polyethylene coating of KOGAS, 3-layer

coating is in principle applied to all straight pipes except for bends and fittings and also applied to river-crossing and off-

shore pipeline sections.

However, another coating system may be employed if specified so. In principle, single layer coating is applied to bends

and fittings. Heat shrinkable material has been applied to the girth weld during construction, while cold tape has been

selected when coating repair for pipeline under operation, which needs not preheating by torch flame.

Pipeline Integrity Assessment and Management System (PIAMS) KOGAS operates its own “pipeline Integrity Assessment and Management Program”, which runs on web browsers. The

system works on the nationwide intra-network which covers all KOGAS and the subsidiary company. The unique system

has been evolved from the own experience. About 6 years ago (1999), KOGAS started its program’s development aiming

to reduce the cost of pipeline management by prioritization of pipeline/segments. At first the stand-alone type program

was developed in 1999. As the enormous data could not be handled efficiently, KOGAS made the decision to expand this

program to web-based versatile multi-user groupware. So the current system had been developed with cooperation of

Head office and Research Division from 2001 to 2002. The program has been utilized since 2003.This program largely

consists of three categories, such as pipeline integrity Management and Pipeline Integrity Assessment, Rehabilitation Plan.

Pipeline Integrity Management is composed of nine sub-menu, such as potential survey(P/S, CIS), coating

maintenance(DCVG), pipe defect maintenance, interference of stray current and alternative current, rectifier maintenance,

underground steel casing pipe, river and off-shore crossing pipeline, excavation and soil resistivity etc.

The person in charge of this system in the head office reviews at third quarter of every year for setting up the plan and

budget for the following year, based on the results of the risk assessment. And the persons in charge of pipeline field

measurement at the branch office enter measured data at their office. Entered data from the branch office update the


on-line database of KOGAS intranet. KOGAS currently operates three LNG terminals and eight branch office. The risk

assessment result is let the operators can determinate the appropriate integrity assessment method. Rehabilitation plan is

to determine the most effective mitigation measures for the identified threats. Those methods can be used in-line

inspection, direct assessment, and other methodologies.

Pipeline Integrity Assessment is to assess all pipeline sections that associated with risk factor.

Total Risk is typically described as two primary factors that consist of ROF and COF. Total Risk can be described as

following.

ROF = Risk of Failure, COF = Consequence of Failure

Fig. 2 ROF and COF factor

ROF is Risk of Failure that the mathematical product of failure probability that some adverse event will occur. ROF factors

consist of corrosion, third party, mechanical integrity and environmental situation surrounding pipe. And COF is

Consequence of Failure that means the result of that event. Those factors include population density, dimension of

accident, types of accident and mitigation activities. Corrosion in ROF consists of environment, design, construction,

operation and maintenance. and mechanical integrity consists of same sub-items as well corrosion. Third party is

composed of environment and prevention measures, and environment damage also same sub-item such as environment

and prevention measures. ROF is made up of total 56 detailed assessment items while COF is 13 detailed assessment

items. COF is made up of population density, dimension of incident, type of incident and mitigation activities.

This system can also be utilized as electronic sanction system and monitoring system of pipeline’s cathodic protection as

well. KOGAS had entered all data available after 1996 into its system until the first half of the year 2003. The first risk

assessment after development of this system was performed at third quarter in 2003. At present Total risk number (COF

Total Risk

0 to 100

Risk of Failure (ROF)

0 to 10

Consequence of Failure (COF)

0 to 10

Corrosion

Mechanical integrity

3rd party construction

Environmental situation Mitigation activities

Type of incident

Dimension of incident

Population density

Total Risk (0~100) = ROF (0~10) × COF (0~10)


× ROF) in assessment criteria should be less than 15.0 and ROF should be less than 3.505. I think these figures should

be changed after two or three year’s trial and error because these criteria are not perfected. Integrity management

program should be continuously operated and should be customized to meet KOGAS’s unique conditions.

According to the result of risk assessment in 2003, Gwaneum-Jungni segment exceeded the risk assessment criteria

15.0 as total risk 15.157 in 153 segments. What the highest risk factor is in this section is a polarized potential and stray

current. So after survey of polarized potential, stray current and ILI survey were applied last year, this section keeps in

good condition on this system now. Based on the risk assessment being performed, KOGAS selected the appropriate

integrity assessment, which is In-line inspection.

Following year, in-line inspection had been conducted by Tuboscope with high resolution MFL tool for Gwaneum-Jungni

section in 2004, but the result in final report was good. Tuboscope reported that the result was calculated by ASME B

31.8G. There was no defect to be repaired the pipeline, Gwaneum-Jungni segment. A caliper tool was run on the 27th July,

2004. This section of the pipeline is 10.616km in length and outside diameter is 20”. The nominal wall thickness is

11.9mm, with additional bend thickness of 14.3mm. The pipeline is constructed from Grade API 5L X65 ERW pipe in 1995.

An instrumented tool of high resolutions type was launched on the 24th August 2004. The survey tool traveled through

the pipeline using natural gas as propellant. The survey time was 2 hours 5minutes, resulting in as average speed of 1.4

m/s. This pipeline section has not been previously inspected. There are several anomalies on this section that do not

display typical characteristics associated with corrosion. Calculation equation used in this inspection is ASME B31G, safety

factor 0.4.

KOGAS performed its second risk assessment with PIAM system in 2004, last year. Because it is the first assessment that

was performed in 2003, this database had some minor problems and some data error, which had later been corrected by

operator. The data for risk assessment can be obtained from the operator in charge of local transmission pipeline’s

cathodic protection. The operator in head office can not review a huge amount of data collected from branch office. All

entered data from local operator can also be provided by system with Import and Export Capabilities, which is connected

to MS Excel format and sources. Operators have corrected some construction data, pipeline information and modified

system error possible so far. This system should be periodically evaluated and modified to reflect improved technologies

and new environment. Data also should be updated and corrected to reflect new information if the system has needs to

be more upgraded as time goes by.

In-Line Inspection

The intelligent pigs for in-line inspection can now provide most of the information required about the condition of a

pipeline, enabling the operator to decide what must be done to rehabilitate it and the means thereafter to regularly

examine it to ensure it remains in good condition. The useful information has been obtained from the in-line inspection

result and enabled decisions to be taken concerning rehabilitation or repair.

KOGAS has inspected the total 1160km for its pipeline integrity using in-line inspection since 1997. This length is 47% of

entire 2451km pipeline of KOGAS. At first, it was started from the section of 26 inches diameter that is from Pyeongtaek

to Mokgam station and performed by service providing company in 1997.


Fig. 3 transmission pipeline network in Korea

But if we take a look at it more in detail, the ILI conducting rate of KOGAS’s pipeline is high because the entire pipeline

can be divided into three categories such as piggable segment, unpiggable segment and segment less than 10 years from

completion. Segment less than 10 years from completion among the total KOGAS pipeline 2,451km is only 616km.

Nevertheless, integrity assessment of pipeline completed with ILI in KOGAS is now up to 1,160km.

Table 1 Transmission pipeline size

Table.2 Operating

Pressure

Pressure(kg/cm²) 70 20 9 Total

Length (km) 2,258 117 76 2,451

Share (%) 92 5 3 100

KOGAS does not consider the regulation associated with the High Consequence Area (HCA) in North America. If there

are sections more than 10 years in any location of the nation, they anyway applied in-line inspection regardless of HCA

because the size of nation’s land is not spacious, and population density is very high.

Size (inches) 36 30 26 24 20 Total

Length (km) 27 1,864 311 47 202 2,451

Share (%) 1 76 13 2 8 100


249 km of total 2,451km would be very costly to make piggable and 34km cannot be pigged due to the low pressure. The

operating pressure of these unpiggable sections is less than 9kg/cm2. There is currently no technology of propelling tool

and maintaining tool’s speed without excursion in running through the line by low pressure gas product, therefore KOGAS

takes into consideration even liquid batching procedures using water instead of its natural gas product as propelling force.

There are major two functions in intelligent pigs. One is geometry pig and the other is MFL pig (Magnetic Flux Leakage).

Geometry pig is measuring ovalities, expansion and reduction of ID, dents, wrinkles, mapping, etc. MFL pig is locating

and measuring any loss of pipe-wall thickness due to corrosion, gouges, or due to any other cause. Geometry pig which

had been developed by KOGAS was named KogasCalGeoTM and applied with our KOGAS pipeline about 500km till end of

2004. In the meanwhile, the MFL pig also has been developing and prototype of MFL has been developed and tested with

pull rig facility. We are going to build the 30 inch-diameter, 300 meter-length pipeline simulation facility in Incheon LNG

terminal. After testing with pipeline simulation facility, we will apply the MFL tool with our pipeline same method as

Geometry pig developing process. The total budget is 5 million US dollar and developing period would probably take

about 7 years and Pipeline Inspection Team in R&D center has been focusing on this particular project for long time to

develop of the pigs.

Fig. 4 Geometry pig developed by KOGAS

Table.3 General Specification of KogasCalGeoTM

Item Specification

Mission Length 500 km

Maximum Operating Speed 8 m/s

Optimum Operating Speed 1 ~ 4 m/s

Minimum passable Bend Radius 1.5D

Maximum Operating Pressure 100 barg

Operating Temperature -10 ~ +60�

Survey Accuracy 1:2000(x,y,z)

Dent & Feature Size & Depth ±2.0 mm

Dent & Feature Orientation ±3 deg.arc

Ovality ±2.0 mm

Curvature Detection ±0.02% strain


Change of Class location to a higher level (now all class-A/ B location)

Pipeline area has been defined as class-A and class-B according to standard for gas pipe thickness selection of KOGAS.

There were three classifications such as class-A, class-B, class-C in the beginning, but it had been changed from three

classifications to two classifications in 1997 because korea’s economic growth rate of local area was very high.

Class-A is classified as city areas defined in the city planning (residential area, commercial area, industrial area and

green-belt area), suburbs to be city-planned in Myun class (or larger class) areas adjacent to cities or town, areas with

heavy traffic and areas with density factor of 46 or over. In case of class-A, Design factor is applied as 0.4. Class-B is

classified as all area other than class-A areas and areas with density factor less than 46. In case of class-B, Design factor

is applied as 0.5. Density factor is the number of households for each 1.6km of a strip centered on the pipeline with a

width of 0.2km each on both sides of it at a certain point of the pipeline. (In the case of the number of household in a

building complex such as an apartment building, the households in the building shall be counted as independent as

independent households). This means that the design factor 0.6 of existing class-C area is changed to design factor 0.5

and 0.6 is annulled. Therefore the distance between block valves is closer than before. It also means three classifications

associated with distance between valves were changed to two classifications, which is 8km to class-A, 16km to class-B,

while 24km to class-C was annulled in 1997.

ECDA (External corrosion direct assessment)

KOGAS has used only DCVG and CIS as indirect inspection. But, the Direct Assessment (DA) process has not been

regularized. The pipeline of KOGAS was designed with sufficient safety factor because of only carrying LNG. So the risk of

internal corrosion and stress corrosion cracking is considered to be negligible. Major concerns to the transmission pipeline

are about external corrosion. The company has analyzed the corrosion environment after the defect has repaired, which

was found by ILI tools. Most of the corrosion was occurred beneath the disbonded coating of girth weld joint and related

to microbiologically influenced corrosion. The most important parameter is the corrosiveness of the soil in this type of

corrosion. KOGAS has a plan to establish the DA process for its un-piggable section. The proposed DA procedure follows

the guide line of the relevant codes like NACE PR0502 and also emphasizes the soil resistivity survey.

They have repaired the damaged coating on the surface of pipeline according to result of DCVG. But now KOGAS is

about to start its integrity assessment with ECDA as tentative tool according to RP NACE 0502-2002. The first section’s

length is 20km called Jochiwon-CheongJu segment. So KOGAS have to decide whether ECDA will be adopted as parts of

integrity management or not after tentative ECDA.

Establishment of NGIS system for transmission pipeline

The gas explosion accidents in Seoul in 1994 and Taegu in 1995 respectively have accelerated the development of

underground facilities management system. The Korean government started to develop integrated underground facilities

management system in 7 areas as sewerage, water, communication, gas pipelines, electricity lines, heating and oil

pipelines.

The GIS information of KOGAS includes as-built drawing, pipeline construction record, report of radiographic examination,

the information of third party activities, and right-of-way, etc may also be searched by KOGAS operator using intranet

system. KOGAS has accumulated the database of buried pipeline and under construction pipeline since 1996. KOGAS has

surveyed its pipelines route and depth from above surface using non-destructive geophysical method called ground

penetrating radar (commonly called GPR). After marking the pipeline’s route and depth above ground acquired by GPR,


these marked points are allocated by GPS coordinates. And these coordinates enter into this NGIS system. KOGAS has

built its database of As-built drawing 2438km out of total 2,451km and completed its survey by GPS 1144km out of total

length of transmission pipeline.

The reason why KOGAS survey using non-destructive geophysical method and GPS coordinates again is according to

introduction of NGIS policy of Korean government since 1998, the coordinate value of national control point is changed.

So it needs to be updated to the NGIS system. The goal of the NGIS master plan is to develop environmentally healthy

land as well as to promote national competitiveness and productivity. It is expected the success of the NGIS Master Plan

to mark a turning point in the management system of our land.

Establishment and operation of the patrol car’s real time monitoring system by GPS

KOGAS has adopted the real-time based location information system by GPS over the patrol vehicle as parts of

improving pipeline safety management. This system can provide quick response and appropriate measures for emergency

situation that may be caused from the transmission pipeline.

This patrol car is equipped with GPS module for location information which enable it to possible to display on pipeline

mapping system from GPS coordinates. This can improve the efficiency of the transmission pipeline operation.

The main function on the web-based system is followings.

Display on the digital pipeline network (Zoom in, Zoom out)

Display on the screen in the Central Control Center real time based location of patrol vehicle

(Patrol vehicle owned and operated by Area Control Center)

Every 3 minute update on display data of individual vehicle

Display the path where vehicle route

Storage of back up data transferred

All block valves are equipped with a Motor Operated Valve (MOV) by remote control

Kogas has to install the block valve in transmission pipeline according to City Gas Business Law.

As mentioned before, the distance between block valves are 8km away for class-A area and 16km for class-B area. If any

incident occurred, this MOV (Motor Operated Valve) could be closed by control center operator and isolate a pipeline

section at the incident spot. To avoid firing and burning, operator can ventilate gases from the pipeline section. The MOV

is always monitored by control center.

As we know, if significant risk exists at some locations as long as gases are being supplied to a rupture site, there may be

fire. So MOV is more effective to isolate ruptured pipe section than manual valve operation.

Pedestrian patrol inspection for area that is difficult to approach by vehicles

As other pipeline operators conduct, KOGAS also patrols underground pipeline’s route and accessories such as test boxes,

gas leakage probations, line marks, sign boards, and land marks etc.

The criteria of KOGAS’s pipeline patrol cycle is twice a day by vehicle. But the problem is that there are areas that patrol

vehicle can not approach to check any damage or third party construction area above ground. Test box above pipeline for

electrical measurement to determine the adequacy of cathodic protection is installed within 300m distance for sacrificial

anode and drainage system and within 500m distance for impressed current system. Gas leakage Probation (GLP) for


checking gas leakage from underground piping is installed at location of both ends of a steel casing or a hume casing for

road crossing and stopple fitting where the line is hot-tapped. Sign Board for marking the location of the pipeline is

installed over buried pipeline in an unpaved road, on the side slope of a paved road, or in its side trench. The distance of

sign boards is 100m or shorter and it is located every turning points and junctions. Especially, there will be 25m in

collective housing area near a gas pipeline where the risk shall be mitigated. Line mark (marking nail) is a marking piece

installed over underground pipeline in a paved road or a paved sidewalk or every junction to mark the location of the

pipeline. Installation spacing is 50m or shorter at paved roads and sidewalks.

KOGAS patrol team’s inspection is performing by a team of two persons. One person gets off the patrol car and

performs the patrol inspection along the surface over the pipeline while the other person drives the car along the pipeline

route. The inspector performs the pedestrian patrol inspection on the basis of 1 to 2 km a day, refraining from inspecting

an excessively long distance in a day. This pedestrian patrol shall be applied once a quarter (three months) to all

pipelines. Cycle of vehicle patrol makes two round trips per day. Therefore the first team’ working time starts at 7 AM and

ends at 4 PM, the second team’s working time is from 10 AM to 7 PM. This means that inspection is performed 4 times a

day periodically for same area.

The vehicle patrol continues all year round even on holidays. Moreover, KOGAS operate Local Area Monitor system. A

person who lives in nearby pipeline route performs the inspection of pipeline instead of patrol car because patrol car can

not approach the area due to the geographical conditions. The responsibility of Local Area Monitor is to call twice a day to

KOGAS’s Area Control Center for the result of pipeline’s inspection performed by oneself.

Isolator and surge protector (ISP)

As I mentioned before, KOGAS apply deep well anode type to corrosion control method of pipeline for its all

underground pipelines. There is an insulation joint for purpose of isolation of pipelines between under ground and above

ground pipeline. It is preventive that lightning or surge can be flowed into above ground pipeline in the gas supply station

from buried transmission pipeline. The ISP blocks the flow of DC current and readily conducts AC current as long as the

absolute value of the voltage across its terminal is less than a pre-selected voltage threshold level (12.5V) and the

steady-state AC current is also within its rating. If either of these conditions is exceeded, the ISP momentarily transitions

from its “Blocking DC / Conducting AC” mode to a virtual short circuit to both AC and DC. This transition is accomplished

within 1 to 4 microseconds by the logic-controlled circuit turning on thyristor.

This equipment is used for main purpose of protecting Insulation Joint because voltage withstanding ability of Insulation

Joint is 25㏁ at AC 5000V 60Hz. KOGAS has the block valve in the middle of the transmission pipeline which is called as

MOV (Motor Operated Valve). The transmission pipeline’s MOV have its own Isolation grounding system while others MOV

have the common grounding system. This means that efficiency of cathodic protection system is not good because

cathodic protection current may flow into pipeline through grounding bar in soil.

Due to the problem, KOGAS considered changing the existing transmission pipeline’s MOV grounding system in 1996. It

is switched from the existing isolation grounding system to the common grounding system using ISP equipment, which

gained the extra advantages in addition to the original purpose of ISP for protecting Insulation Joint in the above pipeline.

Switching MOV’s Isolation grounding to Common grounding system improved the efficiency of cathodic protection system

and reinforced the underground pipeline’s safety because there was a function of Blocking DC / Conducting AC in ISP

equipment. In conclusion, primary purpose of this ISP is that maintains the flowing DC current in the buried transmission

pipeline for cathodic protection while blocking the DC flow into the above pipeline within Gas Supply Station, But KOGAS

utilizes this cathodic protection facilities much efficient ways using this ISP.


Automatic monitoring system for the third party Construction

KOGAS has a R&D program to develop on-line monitoring technique of pipe line damage by third party construction. The

main focus of the current project is on the development of the technique which can detect the vibration from the contact

of construction equipment like hammer drill that produce the distinguishing vibration pattern. The proto type model has

been built and installed at testing section. The device could cover around 10 km range. The device is composed of

accelerometer and signal acquisition unit. The measured signal is transmitted to the server via internet network. When

the signal of the third party construction is detected, the server gives an alarm and sends a message to the patrol team

automatically.

References 1. NACE Standard RP 0502-2002 Item No. 21097 “Pipeline External Corrosion Direct Assessment Methodology”.

2. US Department of Transportation Federal Register. Monday December 15, 2003. Part 2. Research and Special

Programs Administration. 49 CFR Part 192. Pipeline Safety: pipeline Integrity Management in High Consequence

Areas (Gas Transmission Pipeline); Final Rule.

3. Tuboscope pipeline service, Inspection Survey Report( Friday, October, 2004) “Pipeline Survey Report” Korea Gas

Corporation-(Kogas) Rev1. 20” Dry Gas pipeline Job #3425.01 Gwwneum Station to Jungni Station.

4. ASME B 31.8S 2001,” Managing System Integrity of Gas Pipelines”.

5. A.W Peabody edited by Ronald L. Bianchetti “PEABODY’s Control of Pipeline Corrosion” Second Edition. NACE

National International the Corrosion Society.

6. Korea Gas Corporation Standards KOGAS-GSD-2101 “Standard for Inspection of Pipeline accessories” (2002.

10.22 rev2)

7. Website, National Geographic Information Institute in Korea, www.ngi.go.kr/english

8. DEI (Dairyland Electrical Industries) Catalog, Technical Information: ISP P43.

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