value stream mapping and simulation to improve productivity in the installation of natural gas pipes

8/8/2019 Value Stream Mapping and Simulation to Improve Productivity in the Installation of Natural Gas Pipes

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The Construction, Building and Real Estate Research Conference ofthe Royal Institution of Chartered Surveyors

Held at Dauphine Universit, Paris, 2-3 September 2010

ISBN 978-1-84219-619-9

RICS

12 Great George StreetLondon SW1P 3ADUnited Kingdom

www.rics.org/cobra

September 2010

The RICS COBRA Conference is held annually. The aim of COBRA is to provide a platformfor the dissemination of original research and new developments within the specificdisciplines, sub-disciplines or field of study of:

Management of the construction process

Cost and value management Building technology Legal aspects of construction and procurement Public private partnerships Health and safety Procurement Risk management Project management

The built asset

Property investment theory and practice Indirect property investment Property market forecasting Property pricing and appraisal Law of property, housing and land use planning Urban development Planning and property markets Financial analysis of the property market and property assets The dynamics of residential property markets Global comparative analysis of property markets Building occupation

Sustainability and real estate Sustainability and environmental law Building performance


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The property industry

Information technology Innovation in education and training Human and organisational aspects of the industry Alternative dispute resolution and conflict management Professional education and training

Peer review process

All papers submitted to COBRA were subjected to a double-blind (peer review) refereeingprocess. Referees were drawn from an expert panel, representing respected academics fromthe construction and building research community. The conference organisers wish to extendtheir appreciation to the following members of the panel for their work, which is invaluable tothe success of COBRA.

Rifat Akbiyikli Sakarya University, TurkeyRafid Al Khaddar Liverpool John Moores University, UKAhmed Al Shammaa Liverpool John Moores University, UKTony Auchterlounie University of Bolton, UKKwasi Gyau Baffour Awuah University of Wolverhampton, UK

Kabir Bala Ahmadu Bello University, NigeriaJuerg Bernet Danube University Krems, AustriaJohn Boon UNITEC, New ZealandDouw Boshoff University of Pretoria, South AfricaRichard Burt Auburn University, USA

Judith Callanan RMIT University, AustraliaKate Carter Heriot-Watt University, UKKeith Cattell University of Cape Town, South AfricaAntoinette Charles Glasgow Caledonian University, UKFiona Cheung Queensland University of Technology, AustraliaSai On Cheung City University of Hong KongSamuel Chikafalimani University of Pretoria, South AfricaIfte Choudhury Texas A and M University, USAChris Cloete University of Pretoria, South AfricaAlan Coday Anglia Ruskin University, UKMichael Coffey Anglia Ruskin University, UKNigel Craig Glasgow Caledonian University, UK

Ayirebi Dansoh KNUST, GhanaPeter Davis Curtin University, AustraliaPeter Defoe Calford Seaden, UKGrace Ding University of Technology Sydney, AustraliaHemanta Doloi University of Melbourne, AustraliaJohn Dye TPS Consult, UK

Peter Edwards RMIT, AustraliaCharles Egbu University of Salford, UK

Ola Fagbenle Covenant University, NigeriaBen Farrow Auburn University, USAPeter Fenn University of Manchester, UKPeter Fewings University of the West of England, UK


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Peter Fisher University of Northumbria, UKChris Fortune University of Salford, UKValerie Francis University of Melbourne, Australia

Rod Gameson University of Wolverhampton, UKAbdulkadir Ganah University of Central Lancashire, UK

Seung Hon Han Yonsei University, South KoreaAnthony Hatfield University of Wolverhampton, UKTheo Haupt Cape Peninsula University of Technology, South AfricaDries Hauptfleisch University of the Free State, South AfricaPaul Holley Auburn University, USADanie Hoffman University of Pretoria, South AfricaKeith Hogg University of Northumbria, UKAlan Hore Construction IT Alliance, IrelandBon-Gang Hwang National University of Singapore

Joseph Igwe University of Lagos, NigeriaAdi Irfan Universiti Kebangsaan Malaysia, MalaysiaJavier Irizarry Georgia Institute of Technology, USAUsman Isah University of Manchester, UK

David Jenkins University of Glamorgan, UKGodfaurd John University of Central Lancashire, UKKeith Jones University of Greenwich, UK

Dean Kashiwagi Arizona State University, USANthatisi Khatleli University of Cape Town, South AfricaMohammed Kishk Robert Gordons University, UKAndrew Knight Nottingham Trent University, UK

Scott Kramer Auburn University, USAEsra Kurul Oxford Brookes University, UK

Richard Laing Robert Gordons University, UKTerence Lam Anglia Ruskin University, UKVeerasak Likhitruangsilp Chulalongkorn University, ThailandJohn Littlewood University of Wales Institute, Cardiff, UKJunshan Liu Auburn University, USAChampika Liyanage University of Central Lancashire, UKGreg Lloyd University of Ulster, UKS M Lo City University of Hong KongMok Ken Loong Yonsei University, South KoreaMartin Loosemore University of New South Wales, Australia

David Manase Glasgow Caledonian University, UKDonny Mangitung Universitas Tadulako, MalaysiaPatrick Manu University of Wolverhampton, UKTinus Maritz University of Pretoria, South AfricaHendrik Marx University of the Free State. South AfricaLudwig Martin Cape Peninsula University of Technology, South AfricaWilfred Matipa Liverpool John Moores University, UKSteven McCabe Birmingham City University, UKAnnie McCartney University of Glamorgan, UKAndrew McCoy Virginia Tech, USAEnda McKenna Queens University Belfast, UKKathy Michell University of Cape Town, South AfricaRoy Morledge Nottingham Trent University, UK


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Michael Murray University of Strathclyde, UK

Saka Najimu Glasgow Caledonian University, UKStanley Njuangang University of Central Lancashire, UK

Henry Odeyinka University of Ulster, UKAyodejo Ojo Ministry of National Development, SeychellesMichael Oladokun University of Uyo, NigeriaAlfred Olatunji Newcastle University, AustraliaAustin OtegbuluBeliz Ozorhon Bogazici University, TurkeyObinna Ozumba University of the Witwatersrand, South Africa

Robert Pearl University of KwaZulu, Natal, South AfricaSrinath Perera Northumbria University, UKJoanna Poon Nottingham Trent University, UKKeith Potts University of Wolverhampton, UKElena de la Poza Plaza Universidad Politcnica de Valencia, SpainMatthijs Prins Delft University of Technology, The NetherlandsHendrik Prinsloo University of Pretoria, South Africa

Richard Reed Deakin University, AustraliaZhaomin Ren University of Glamorgan, UKHerbert Robinson London South Bank University, UKKathryn Robson RMIT, AustraliaSimon Robson University of Northumbria, UKDavid Root University of Cape Town, South AfricaKathy Roper Georgia Institute of Technology, USASteve Rowlinson University of Hong Kong, Hong KongPaul Royston Nottingham Trent University, UK

Paul Ryall University of Glamorgan, UK

Amrit Sagoo Coventry University, UKAlfredo Serpell Pontificia Universidad Catlica de Chile, ChileWinston Shakantu Nelson Mandela Metropolitan University, South AfricaYvonne Simpson University of Greenwich, UKJohn Smallwood Nelson Mandela Metropolitan University, South AfricaHeather Smeaton-Webb MUJV Ltd. UKBruce Smith Auburn University, USAMelanie Smith Leeds Metropolitan University, UKHedley Smyth University College London, UKJohn Spillane Queens University Belfast, UKSuresh Subashini University of Wolverhampton, UKKenneth Sullivan Arizona State University, USA

Joe Tah Oxford Brookes University, UKDerek Thomson Heriot-Watt University, UKMatthew Tucker Liverpool John Moores University, UK

Chika Udeaja Northumbria University, UK

Basie Verster University of the Free State, South AfricaFrancois Viruly University of the Witwatersrand, South Africa

John Wall Waterford Institute of Technology, IrelandSara Wilkinson Deakin University, AustraliaTrefor Williams University of Glamorgan, UK


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Bimbo Windapo University of Cape Town, South AfricaFrancis Wong Hong Kong Polytechnic UniversityIng Liang Wong Glasgow Caledonian University, UKAndrew Wright De Montfort University, UKPeter Wyatt University of Reading, UK

Junli Yang University of Westminster, UKWan Zahari Wan Yusoff Universiti Tun Hussein Onn Malaysia, Malaysia

George Zillante University of South AustraliaBenita Zulch University of the Free State, South AfricaSam Zulu Leeds Metropolitan University, UK

In addition to this, the following specialist panel of peer-review experts assessedpapers for the COBRA session arranged by CIB W113

John Adriaanse London South Bank University, UKJulie Adshead University of Salford, UKAlison Ahearn Imperial College London, UKRachelle Alterman Technion, IsraelDeniz Artan Ilter Istanbul Technical University, Turkey

Jane Ball University of Sheffield, UKLuke Bennett Sheffield Hallam University, UKMichael Brand University of New South Wales, AustraliaPenny Brooker University of Wolverhampton, UK

Alice Christudason National University of SingaporePaul Chynoweth University of Salford, UK

Sai On Cheung City University of Hong KongJulie Cross University of Salford, UK

Melissa Daigneault Texas A&M University, USASteve Donohoe University of Plymouth, UK

Ari Ekroos University of Helsinki, Finland

Tilak Ginige Bournemouth University, UKMartin Green Leeds Metropolitan University, UKDavid Greenwood Northumbria University, UKAsanga Gunawansa National University of Singapore

Jan-Bertram Hillig University of Reading, UKRob Home Anglia Ruskin University, UK

Peter Kennedy Glasgow Caledonian University, UK

Anthony Lavers Keating Chambers, UKWayne Lord Loughborough University, UKSarah Lupton Cardiff University

Tim McLernon University of Ulster, UKFrits Meijer TU Delft, The NetherlandsJim Mason University of the West of England, UKBrodie McAdam University of Salford, UKTinus Maritz University of Pretoria, South Africa


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Francis Moor University of Salford, UK

Issaka Ndekugri University of Wolverhampton, UK

John Pointing Kingston University, UK

Razani Abdul Rahim Universiti Technologi, Malaysia

Linda Thomas-Mobley Georgia Tech, USAPaul Tracey University of Salford, UK

Yvonne Scannell Trinity College Dublin, IrelandCathy Sherry University of New South Wales, AustraliaJulian Sidoli del Ceno Birmingham City University, UK

Keren Tweeddale London South Bank University, UK

Henk Visscher TU Delft, The Netherlands

Peter Ward University of Newcastle, Australia


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Value stream mapping and simulation as integrated lean approach tool for improving

productivity in the installation of natural gas pipes

Mok, Ken Loong

Master student, Department of Civil & Environmental Eng., Yonsei Univ., Seoul, [email protected]

Sin, Eon IllMaster student, Department of Civil & Environmental Eng., Yonsei Univ., Seoul, [email protected]

Han, Seung HeonProfessor, Department of Civil & Environmental Eng., Yonsei Univ., Seoul, [email protected]

Jang, Woosik Master student, Department of Civil & Environmental Eng., Yonsei Univ., Seoul, [email protected]

Abstract

From ancient Egypts pyramids to Qin Shi Huangs terracotta army, and onto Henry Fords Model T,

cogitations of pre-existing waste-reduction similar to todays lean-thinking have been practiced by

several forerunners. With the contemplation of the past and the origin of the modern worlds lean-

thinking outlined, an introduction to lean construction was given. The role of value stream mapping(VSM) and simulation as tools in implementing, analyzing and evaluating lean construction have been

studied separately by numerous researchers. Hence, this paper attempts to apply both methods as

integrated lean approach for productivity improvement. A case study was carried out on a natural gas

pipe works. The current-state of the value-stream-map was drawn and analyzed to identify the waste

related to lean management. On top of that, a detailed value-stream-map of individual processes against

time frame was studied to extrude more hidden wastes. Simulation models for current ( as-is ) and

improved ( to-be ) natural gas pipe operations were developed using the EXTEND simulation software,

whereby the improved natural gas pipe operations showed better results in all aspects of the process

utilization and productivity. This study showed that VSM and simulation tools, when combined together,

form a strong integrated instrument for improving work productivity.

Keywords : Lean construction; Value stream mapping (VSM); Simulation; Productivity improvement

1. INTRODUCTION

Lean construction has long been discussed by numerous researchers. Practical examples of the lean

approach in construction were conducted using developed tools, such as value stream mapping (hereafter


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called VSM) and simulation. However, focus was usually placed on a single tool and its greatness onto

the other. Instead, it might be better to consider the integration of both evaluative tools in a manner

whereby they could complement each other. This paper discusses the above mentioned matters plus some

insights down the discovery lane of lean thinking. The structure of this paper is as follows. In part 1, we

discuss waste-reduction prior to the well acknowledged lean-thinking principle. The history of leanthinking is examined to enable a greater understanding of its development and, subsequently, its

extension towards lean construction. Part 2 describes the VSM and simulation methods as efficient

integrated tools in implementing, analyzing and evaluating lean construction. It also reviews the literature

related to the topic in question. Part 3 details the procedural methodology adopted in the present study. A

case study for a natural gas pipe installation works is then carried out and the current-state value stream is

mapped and analyzed in part 4. In addition, the lean techniques are implemented in order to eliminate the

waste in the current system. On the basis of as-is analysis, leaner future-state map is proposed. Then,

both simulation models of the current and improved states were modeled, validated and analyzed. Finally,

part 5 discusses a short conclusion and suggestions for the future study.

1.1 The forebear of lean thinking

Having gained much assurance since its introduction in the last decade of the twentieth century, lean-

thinking continues to inspire us to attain new heights in building better system for our current world and

perhaps the promising future. For a lay man, lean would carry the meaning of economical or little

waste . Lean thinking, thus, was introduced as a means to reduce the waste through identification and

elimination of waste which was defined under lean-management. Nevertheless, there exist numerous

sources that quoted the existence of waste-reduction thinking long before the acknowledgement of the

just-in-time (JIT), the Toyota Production System (TPS), and the relatively newer idea of lean production.

Over the years, similar concepts that are now seen as being the key to lean have been discovered and

practiced by manufacturers and investors in order to improve productivity and eliminate waste in their

production systems. It has been claimed that the application of lean-thinking in mass production appeared

as early as 2600 B.C. when the Egyptians built the pyramids (Kenneth Wong, 2007). Wong reported that

a French architect named Houdin devised a new theory pertaining to the construction methods employed

by the Egyptians at Giza (2570-2500 BCE). Houdins theory supposed that waste was eliminated during

the construction of the pyramids through the reuse of the stones dismantled from the external ramps to

build internal ramps for the completion of the pyramids. The external ramps were temporary ramps for

transporting millions of tons of stone to approximately 2/3 of the pyramids mass.

We believe that more such historical examples of waste conservation will be discovered in the future. We

should encourage more participation from our very own construction academia to unmask the mystery of yet another predecessor of lean construction applicants among various world heritages and megaliths that


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survived the past age. For example, Qin Shi Huang s Terracotta Army is the largest ceramics project ever

known, whereby each figure was formed by joining separately created bodily sections (Asian Art

Museum, 1999). These terracotta sculptures were claimed to be an early feat of mass production and

assembly line production, with the specific parts manufactured and joined together in various

combinations whilst be monitored for quality control ( J. Portal, 2007, Museum of the Terra-cottaWarriors and Horses of Qin ShiHuang).

William A. Levinson (2002) once mentioned that the philosophy behind the revolutionized Japanese

manufacturing was the same as the Ford Motor Company. He also mentioned how Ford was influenced

by Benjamin Franklin on issues of waste. Henry Ford, in his book entitled My life and work, states that

he had applied the principles of waste-reduction, the essence of lean-thinking, when he investigated a

foreign valve strip stem made from French steel and eventually improved his steel by adding vanadium.

Vanadium was added to the steel in order to produce lighter yet stronger car parts which subsequently

reduced the weight of the car. Reducing a cars weight is a great approach to minimizing the waste of

energy and materials. Lighter parts also shorten the handling time of the parts throughout the joining

process, and most importantly, increased the value of the products.

No business can improve unless it pays the closest possible attention to complaints and suggestions.

(Henry Ford, 1922). Though confident in the quality of his cars, Ford always showed a keen interest in

the customer feedback related to the quality of the Ford cars. This is similar to the pull philosophy of

the recent customers-driven concept in lean thinking. Pull is one of the techniques in lean production

involving materials being pulled through the production flow to meet the expectation of the customers

(Tommelein, 1998).

1.2 The origin of lean thinking in the modern world

Despite the historical evidence present herein, we cannot deny the fact that systematic concepts of lean-

thinking actually surfaced in the 1980s and were outlined by a team of researchers at MIT after an

extensive study of the manufacturing processes, under the International Motor Vehicle Program (IMVP),

of the motor industry. In their classic book The Machine That Changed the World (Womack, Jones and

Roos, 1990), the development of lean manufacturing practices in the automobile industry was discussed

in detail. Such lean production principles had been systematically applied by Japanese car maker Toyota

for decades since the 1960s, but were only made known to the world in the 1980s. The overwhelming

responses to Womacks study led to the term of lean production first called being coined by Krafcik in

1988 (Holweg, 2006).

Eventually, the concept of lean was introduced into one of the oldest and change-resistant construction-


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industries following the devisal of Lean Production by Koskela in a 1992 report. Following notable

success in the manufacturing sector, such as industrialization, computer integration and automation, the

concepts of lean production were also imported to the construction industry. Ballard and Howell (1998)

reasoned that a lean revolution in the construction industry could lead to the conceptual overthrow of the

established flow and value models.

2. EFFECTIVE TOOLS FOR LEAN CONSTRUCTION AND APPLICATIONS

2.1 The roles of value stream mapping (VSM) and simulation

To date, the construction industry had focused mainly on waste reduction (Ballard and Howell 1998).

Hence little research has been conducted pertaining to the improvement of value maximization in the

construction industry. One way to indentify the in-place value for the existing system is through the

evaluation and validation tools of lean techniques, such as VSM and simulation. VSM is a visualization

tool that was first used in the Toyota Production System and is known as Material and Information Flow

Mapping. The Toyota engineers characterized the existing and future states of their process & operations

in order to implement lean elements into their developmental system plans (Rother and Shook, 1998). A

value stream is the combined flow of all of the operations, including both non-value added and value

added activities, required to produce the end product for a customer. Such a system is first mapped out in

2-D. This practical communication tool provides a clear view of the flow of information as the

production process progresses through the value stream; hence, it enables easy visual detection of sources

of waste. After identifying waste, one can design an improved future-state map by implementing lean

techniques into the current value-state map.

No other tools are more suitable than VSM for displaying the connections between information flow and

material flow (Rother and Shook, 1998). The recommended practice is not to spend too much time

ensuring every detail of the future-state map is perfectly flawless. Re-adjustments and fine-tuning of a

future map following its implementation may save us from rework and waste efforts. Lean-thinking is the

art or tactics used for command, while validation tools can be regarded as the instruments for evaluatingthe various maneuvers. Validation tools are becoming more important in implementing lean thinking due

to the rapid development of complex project under booming economies. The advancement of technology,

especially in the information and computing sector, has provided the investors with the required

technology to implement lean-thinking to its entirety in the construction industry. A good example is the

computer simulation. Researchers have proved the roles of simulation as an evaluation tool in shaping the

very illustration of the benefits contributed by lean construction towards the industry. In fact, lean

thinking and simulation are closely linked and indeed synonymous, provided that the processes are

efficiently modeled and analyzed as the real operations (Halpin and Kueckmann 2002).


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2.2 Review of lean construction applications

The construction industry has not paid enough attention to the benefits, and real value of lean-thinking

partly due to the difficulty in implementing a lean approach. Yu et. al. (2009) mentioned the lack of

practical examples of a VSM in lean construction. Hence, further research based on effective tools, suchas VSM and simulation, is required to practically extend lean thinking in construction society. Quite a

numer of lean construction simulation studies now exist thanks to the advancement of computing

technology. Tommelein (1998) used simulations to improve pull technique construction processes. This

study described three alternatives of supply chain models and provided simulations that reflected the

significant difference in the output of a lean model and a control model. Halpin and Kueckmann (2002)

concluded that lean-thinking provides a structured format while its performance and advantages can be

evaluated through simulation. As the use of simulation is now some four decades old, powerful

simulation tools have been developed along with strategies for their usage. Simulation technique has now

further advanced to involve 3D motion paths in dynamic animations of simulated construction processes

(Martinez and Ioannou 1999; Kamat and Martinez 2007), thus emphasizing the visualization and

technical aspects of the tools.

On the other hand, there are only limited studies that have employed the VSM technique along with the

implementation of lean construction. Such studies have focused mostly on the resource supply chain or

the flow of components in a manufacturing-cycle domain. Thus they did not track the course of upright

lateral processes (for example, the idling time of a machine before its next task) or evaluate the value

stream against time. Arbulu et. al. (2003) conducted a value stream study for a re-engineered construction

supply chain for pipe supports used in power plants. These authors successfully identified opportunities

for improvement through the VSM. In their research, the researchers studied the VSM workflows, which

involved the engineering firm and its supplier in one single connected stream. They, however, ignored the

development at each individual host in the understanding that it was not necessary to map the value

stream of the engineering firm for its other daily works. More recently, Alves et al. (2005) applied lean

production concepts and VSM for make-to-order products in a job shop environment. Job shop is related

to business that specializing in manufacture of custom made parts. They corrected the inefficiencies in

the current-state value map and presented a future-state value map. Despite their contributions, there

were no VSM studies for individual operations against time, even though the operators might be idle for

half of the time behind the backdrop.

In manufacturing production, researchers investigate the process flow by tracking the direction of the

products components or work-in-progress (WIP) on a conveyor belt leaving the host of an individual

process behind for its next task. However, it is the other way round for construction whereby the endproduct is stationed at a fixed place. The product passes through different sub-trade processes brought in


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through the conveyor belt. The main factor contributing to a smooth flow is the efficiency of this

moving belt to deliver the available resources. With good management through the application of the JIT

method or a sufficient inventory, mass production in manufacturing today is able to ensure the continuity

of the resources delivered by the conveyor belt to each process host without much delay. The waste or

values that are lost invariably occur at the interfaces between processes (Arbulu et. al. 2003). Hence, it isnecessary to study the characteristics of the virtual conveyor belt in order to provide a smooth supply

of resource for a fixed place product in the construction industry.

Often in construction, different tasks cannot be carried out simultaneously. This mean that one resource is

idle on the conveyor belt before its forerunner completes an earlier task. This is worsened by variation

of sub-trades or crews who tend to follow their own working schedules, not to mention the different

interests of individual parties. There is much to be studied behind the scenes for every host of a process

while they were placed on the belt.

Wang et. al. (2009) argued that simulations are more practical and powerful than VSM as a modeling and

evaluative tool for complex and dynamic systems. VSM has been called a static snapshot that is unable to

express the dynamic nature and uncertainty inherent to an interconnected system. However, Wang et al.

did not explain how they identify waste in the current process map before they started using simulation

models for improved state (future state). We think that VSM and simulation is not separable when

dealing with the context of indentifying waste and subsequently modified for improvement. Indeed, the

process of identifying waste prior to simulation is no other than practicing VSM itself. Any

understanding towards a process or scratch of idea for value-waste detection would have long been

executed initially in a mind-map, before transferring into a visualized form of computer simulation. Not

only the vision and model come from the value-stream-map, the data gathered thru VSM make

information for simulation setup available (Donatelli and Harris 2001). We did not test VSM and

simulation as if they were two isolated tools. Instead, we combined both to form a single integrated tool.

We then tested this integrated tool as a means for implementing the lean approach to improve

construction productivity. If VSM is a snapshot, simulation is the movie. (Donatelli and Harris, 2001).

VSM snapshots therefore act like the individual frames of an animation: if you flick through the

snapshots in sequence, you will see the process motion.

3. METHODOLOGICAL RESEARCH PROCEDURES

The current paper begins with a brief literature review pertaining to the development of lean-thinking in

lean construction. A case study is then conducted to obtain real field data together with the advice of

experienced personnel. We interviewed the supervisors responsible for the installation works. Thesupervisors opinions were obtained pertaining to the sequence of natural gas pipe works and likely


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duration of certain operations.

Our data was analyzed by both the VSM and simulation methods. The process system was first

represented by a value-stream-map and any opportunity for improvement through the elimination of

waste was identified. Next, a more detailed value-stream-map was delineated to show the specific typesof waste generated by individual operations against time. Similar identification for improvement

opportunity was again conducted.

Simulation model was made and validated to represent the real operation. An improved model was made

based on the suggestions obtained from the VSM. Simulations were conducted to assess the results of our

improvements after the implementation of the lean approach. Models were developed using EXTEND

simulation software. These were compared to the real process. Thus, the integrated VSM and simulation

methods were used to devise a framework for the systematic implantation of the lean approach. As a

result, through field observations, process modeling, and operational reengineering, we have been able to

suggest improvements in productivity.

4. CASE STUDY

In this paper, a case study was conducted in a natural gas pipe works in Korea. The construction work

processes under study included the interactions of all of the construction elements from the materials to

the equipments to the work force.

Natural gas pipe works by KOGAS (Korea Gas Corporation) were selected as the case study for this

paper. KOGAS was incorporated by the Korean government in 1983 and has grown to become the

worlds largest LNG importer, with a nationwide pipeline network of 2,739 km. The construction and

operation of LNG terminals and its natural gas distribution network are among the main business

concerns of KOGAS. Hence, a good and efficient way of building the pipelines would be of great benefit

to the gas company.

The Pyong Taek Yongin pipeline construction site was particularly observed. The simplicity and

repetitiveness of this operation became the main reason for it to be selected as the case study in our

research. On top of that, the cycle time of a natural gas pipe installation can be observed easily, hence

increases the chances of detection of opportunity for improvements. This project began in June 2008 and

is scheduled to be completed in December 2011 (3.5 years). The cost of construction is approximately

estimated at USD 61.2 million in total and involves two main contractors: Daerim Engineering &

Construction and Doosan Heavy Industries & Construction.


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4.1 Work flow diagram and current state map

The natural gas pipes facility setup is an operation involving multiple processes and the coordination of

different parties. Though not as many trades are involved as with the building construction, the issues of

safety, land, and the publicly used environment have presented limitations to the operational flow of thenatural gas pipe installation. Other limitations include space, lengthy inspections, and non-flexible

sequences. Productivity goals cannot be achieved at the expense of control factors such as safety and

public interest. Therefore, it is important for us to study the operational system carefully in order to

identify possible improvements. The operation started with excavation of a trench. Two dumping trucks

were served by an excavator with a service time of 5 - 8 minutes. In case of restraints due to underground

utilities or during asphalt clearing, the service time would range from 12 to 30 minutes. The travel time to

and from the dumping site was around 12 - 17 minutes per trip. Gas pipes were fixed in 12 m length.

Hence, the task of pipe loading (pipes being load down to the trench by crane truck), following the

excavation of the trench, could only commence when the length of the trench was sufficient (> 12m).

Since the natural gas pipes were to be buried under the road, the operation took place at the existing

double lane road whereby one lane was closed to allow for the construction. Workers were assigned to

control the traffic as only one way traffic was available. Whenever the trucks came or departed, the

traffics in the remaining open lane was disturbed to some extent. Figure 1 shows the work flow diagram

for installation of natural gas pipes excluding the asphalt-repave works at a later stage.

Three welders were needed to weld the joint between two pipes. The welding process took approximately

135 minutes before the joint was ready for inspection by the non-destructive test (NDT) technicians. The

NDT took approximately 30 minutes and the test results were available after an hour. The average rate of

fail results is relatively low at less than 2%. The welders started their next task if no further touch up of

welding was needed. After the pipe connections passed the NDT, grinding and coating began for

approximately 40 minutes to be followed by backfilling activities. Backfilling of the completed pipeline

involved several stages of sand filling, protection board placing, backfilling of suitable material (earth)

and land mark setup. The covered trench was not repaved as there was not enough length of accumulated

sub-base to be paved until one or two weeks ahead. Therefore, the laying of the pavement was excluded

from this study. Fig. 2 shows the current-state value-stream-map representing the production flow for a

natural gas pipe installation. The proportion of non-value added activities (NVAA) were found to be very

low compared to the value added activities (VAA). That is largely because this current-state value-

stream-map cannot fully represent the value stream of the actual operation and thus accurately identify

the existence of waste. A more detailed value-stream-map is thus required such that more detailed and

breaks down individual processes can be laterally displayed against time.


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4.2 Findings from the current system and suggestions for improvement

Figure 3a and 3b show the breakdown of the value stream for the individual sub-processes conducted on

the study against time. The percentage of non-value added and unnecessary activities for welders and

grinders-coaters were 30% and 76.5% respectively. There might be an alternative way of reducing the


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idling time of workers by merging their tasks and allocating a team of multi-taskers. However, in the case

of natural gas pipe operations, the grinders are semi-skilled labor and the welders are skilled labor; hence,

the grinders are not able to do the welding jobs. Utilizing welders to do the grinding and coating jobs

would be a waste of wages. Moreover, concurrent welding and coating of different joints cannot be

carried out if the welders are required to complete all of the treatments to a joint, including grinding andcoating.

An alternative way to improve the labor utilization and reduce the idle time for workers is by reducing

the waiting time of third parties (welders, NDT technicians, etc.) for the completion of trench excavation

before the pipe can be set up and welded. Normally, the first task of the day is the excavation of the pipe

trench, which last for 2 - 3 hours before there is enough space for pipes to be loaded and connected by

welding. We suggest utilizing the idle time of the excavator on the day before while waiting for the

completion of the welding, NDT, and coating process. The excavator could excavate additional lengths of

the buffer trench for the following days pipe works. However, the danger of leaving open trench exposed

overnight must be considered. We thus proposed that the pipes be loaded into the open trench which

would then be filled in with sand so as to increase the stability of open trench. Figure 4(a) and (b) show

the current and proposed revision of the pipe works over a period of three days respectively. Currently,

the contractor is able to connect and treat two connection points per day. The proposed revision of this

procedure calls for an extra excavation for one pipe length and the unloading of an additional pipe per

day. Although the welding for this new loaded pipe cannot be done on the same day, it enables the

welders to commence work early the next day, hence increase the possibility of treating three connection

points per day. Figure 5 shows the proposed future-state value-stream-map. The increase of the open

trench buffer to one extra pipe length per day will eliminate the idling of the excavator, the trucks and

will allow welding to start concurrently with the excavation on the following work day. Hence, overall

productivity can be improved over the downstream activities.

4.3 Simulation as an evaluative tool complementing VSM

In the previous part, the waste generated and opportunities for improvement were identified through

VSM as part of our lean approach. However, the static nature of VSM has limits its ability as an

evaluative tool for the dynamic system of a real construction site, especially in operations involving

interrelated tasks and common operators assigned with multiple-tasks. Simulation is a good complement

to VSM when evaluating the lean approach for a construction process. In this case study, the excavator

and dumping trucks were needed for both excavation and backfilling; hence, both tasks could not be

carried out concurrently at different places. In our case study, the grinding and coating were done by the

same team of grinders. A simulated model for a natural gas pipe operation was produced using EXTENDsimulation software. The model was designed to provide an algorithm for making sure the upstream tasks


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were given priority for the resources. Other sequences of different events were also tested for potential

improvement. Figure 6 shows the natural gas pipe operational model ( As-is ) which consists of three

hierarchy blocks named Excavation, Pipe Treatment and Backfilling. Each hierarchy block

contains other blocks that represent a portion, or subsystem, of the model.

The first hierarchy block for the excavation involved two numbers of dump trucks and an excavator. The

Daily Program block fixed the daily start time for work across three consecutive days. The duration of

the work day was 8.5 hours or 510 minutes, after the rest time had been eliminated (refer Figure 7). The

fill-in capacity of dump truck corresponding to the run length of the open trench was approximately 1.5

m of trench per truck. The Excavation block represents the operation of the excavator serving the empty

trucks. The service time of the excavator was set at 6.5 minutes. The trucks were held at the stack block

until they were needed according to FIFO (first-in-first-out) order. The resource pool of the Trench

(1.5m) block represented the number of dump truck trips required per day (excavation). The space

required for one pipe was 12 m in length. As only two pipes were installed per day, a minimum (24 m

/1.5 m) = 16 trips were required per day. Figure 8 shows the subsystem for the excavation involved in the

first stage of natural gas pipe operations.

The second hierarchy block consists of the treatments applied to the connection joints of the natural gas

pipes. After the loading of a pipe into the open trench, welding is carried out followed by the non-

destructive test (NDT). The welders are required to standby while the test takes place. If the connection

joint passes the test, the grinders start coating the joints. Figure 9 shows the sub-system for pipe

treatment in the hierarchy block.

The third hierarchy block is the Backfilling block involving the backfilling of sand and suitable

materials into the excavated pipe trench. External sand resources are used for the backfilling. Manpower

is needed along with machinery during sand filling to avoid damaging the installed gas pipes with the

machinery. Sand filling and compaction is followed by laying down protective board and then filling in

the trench with earth. The capacity of the dumping trucks corresponds to the run length of the half-open

trench at approximately 3 m of trench per truck. The Unload Earth block entails the dumping truck

unloading its load for backfilling. Figure 10 shows the backfilling subsystem nested in the hierarchy

block.


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4.4 Simulation-based evaluation of the current system

Our results showed that the excavator and dump trucks were utilized as 51% and 47% respectively. These

percentages are relate to the non-idling time of machineries. The excavation of the trench was completed

at six counts with six connection joints welded and five pipes coated and buried at the end of three days

(refer Figure 6 and Figure 9).

In actual construction site, the utilization of welders and grinders-coaters were 58% and 16%. Our

simulation showed that the welders and grinders-coaters were utilized at 53% and 15% respectively.These percentages are relate to the non-idling time of workers and these figures are similar to those we


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obtained from our VSM. Figure 11 shows the utilization graph for the welders (first and highest graph in

blue), NDT technicians (second graph in green), coaters (third graph in grey) and grinders (lowest graph

in red) in the current system. Two peaks (two pipes welded per day) can be found for each work day of

welders, which corresponded to two numbers of pipe joints treated per day in actual construction site.

However, there were only five joints being coated in three days (five peaks).

4.5 Improved model (To-be)

The revised model was set to have a resource pool named trench to be excavated to a length of 36 m

(three pipe lengths). The resource pool named Trench (1.5m) represents the number of dump truck trips

required per day in order to excavate the required length of the open-space trench. The length required

for 1 pipe is 12 m. In the old system, only two pipes were installed and treated per day. Our VSM showed

that this process could be improved by loading an additional pipe into the trench per day so that welding

could commence at the start of the following work day. In this way, delays due to uncompleted trenchexcavations could be reduced. Hence, in the new system, a minimum (36 m /1.5 m) = 24 trips of earth

removal works are required per day.

Figure 12 shows the revised model excavated eight pipe lengths, treated six joints completely and bury

five pipes in three days. The excavator and dump trucks were utilized at 71% and 66% respectively, both

projected an improvement of around 40% compared to the as-is model. The welders and grinders-coaters

were utilized at 61% and 18%, respectively, projected an improvement of 15% and 20% respectively

compared to the old system. Figure 13 shows the utilization graph for the welders (blue), NDTtechnicians (green), coaters (grey) and grinders (red) for the to-be model. Six peaks (six pipes treated in


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three days) can be found, which corresponded to two numbers of pipe joints treated per day. An

additional peak (additional joints) is not properly formed at the end of welders graph due to the end of

the time period. The welding works will be continued and commence at the start of the following day

without delay, hence increasing the chance of treating three joints at the following day again. There were

six joints being coated in three days (six peaks), an additional joint or 20% improvement compared to theModel as-is . Table 1 shows the comparison between the Model as-is and model to-be .


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5. CONCLUSION

The current study reviewed the pre-existing methods of waste-reduction that precede lean thinking in

achieving a more efficient operational system. The current study has presented a clearer picture for the

use of lean though in construction, the laying of gas pipes to be specific. We believe that any simulation

model would have started as a systematic value-stream-mapping whereby the values and waste were

identified when re-designing an improved ( to-be ) operational system. Thus, the present study examined

the possibility of systematically implementing a lean framework using an integrated VSM and simulation

method.

The case study described herein involved a natural gas pipe laying site. The current-state value stream for

the site was mapped and the opportunities for improvement ware identified. On top of an original flow

value-stream-map, a more detailed value-stream-map was drawn up that broke down the individual

processes against time in order to identify those sources of waste that the plain flow map missed. The

downstream operators were found to be idling. The pull signals from downstream were not being

captured to increase the inventory or to buffer the excavated trench upstream for immediate pipe

treatments. The idling of the excavators and dump trucks was reduced when they were assigned an

increased excavation load in order to provide a buffer in terms of the pipe loading space. The simulations

for our current ( as-is ) and improved ( to-be ) work schedules for the laying of natural gas pipes were

modeled using the EXTEND simulation software. The latter showed improved results in all aspects of

process utilization, queue time, maximum wait time and productivity.

Our proposed improvements require validation in a real operational environment. The natural gas pipes


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experts have stated that it is the safety issue involved in leaving an additional open trench exposed

overnight that is the main drawback to our suggested improvements. Perhaps future research could

propose temporary solutions to increase the safety of open-trench buffers. However, this study has shown

that the VSM and simulation methods can be functionally integrated to provide a stronger instrument in

the search for solutions to productivity shortfalls. Future studies, therefore, could focus on developingmore potential applications for the integrated VSM and simulation method in operations of greater

complexity.

Acknowledgements

This research was supported by the Basic Science Research Program through the National Research

Foundation of Korea (NRF), a grant funded by the Ministry of Education, Science and Technology

(2009-0081326). The authors would like to acknowledge the contributions of KOGAS personnel and Dr.

Sean Ramnarine for their valuable feedback on this text.

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