Improving the quality of cleaning the surface of the shield by high pressure water jetting method at vivablast (vietnam) co , ltd

for allowing me to practice and complete my graduation thesis this semester with the topic: Improving the quality of cleaning the surface of the shield by high-pressure water jetting met

MINISTRY OF EDUCATION AND TRAINING

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION

FACULTY FOR HIGH QUALITY TRAINING

THESIS

IMPROVING THE QUALITY OF CLEANING THE SURFACE OF THE SHIELD BY HIGH-PRESSURE WATER JETTING METHOD AT VIVABLAST

COMMENTS OF ADVISOR

………

………

……….………

……… ………

………

………

………

………

………

………

………

………

………

………

………

………

………

………

………

HCM city, day … month … year 2022

Advisor

Nguyen Thi Mai Tram

COMMENTS OF REVIEWER

………

………

……….………

……… ………

………

………

………

………

………

………

………

………

………

………

………

………

………

………

………

HCM city, day … month … year 2022

Reviewer

ACKNOWLEDGEMENTS

Dear:

Board of Management of Vivablast (Vietnam) Co., Ltd

Mrs.Nguyễn Thị Mai Trâm – Lecturer at Ho Chi Minh City University of Technology and Education

My name is Pham Ngoc Duy (student ID: 17146012) - a graduate thesis student in the first semester of the academic year 2022-2023

First of all, allow me to thank Vivablast (Vietnam) Co., Ltd for allowing me to practice and complete my graduation thesis this semester with the topic: Improving the quality

of cleaning the surface of the shield by high-pressure water jetting method at Vivablast (vietnam) Co., Ltd

I would also like to express my sincere thanks to Ms Nguyen Thi Mai Tram - my direct advisor for this graduation thesis In more than two and a half months of working on my graduation thesis, I have been guided in detail about the outline, presentation, and detailed content suggestions for this topic Thanks to her dedicated help, I can not only complete my graduation thesis better but also have a better overview of the topic I am writing about That helps to lay the foundation for building and defending this thesis before the committee

In the end, although I have tried to do this graduation thesis as best as possible, I will inevitably make mistakes I hope that Vivablast company, Mrs.Tram, and readers understand Above all, I would be happy to receive further feedback from Vivablast,

Ms Tram, and readers to improve this report

Sincerely Thanks and Best regards

HCM city, day … month … year 2022

Student

Pham Ngoc Duy

LIST OF ABBREVIATION

ISO International Organization for Standardization NACE National Association of Corrosion Engineers International

QCVN

40:2011/BTNMT

National technical regulation

on industrial wastewater (vietnam)

TNHH Vietnamese: Trách Nhiệm Hữu Hạn / English: Company

Limited

LIST OF TABLE

Table 2 1 Quality standards for cleaning the surface of the shields 15

Table 2 2 Traditional AHP pairwise comparison matrix 18

Table 2 3 Normalised Pairwise Comparison Matrix 18

Table 2 4 The random index corresponds to the number of selection criteria considered 19

Table 3 1 Popular types of water jetting machines on the Vietnamese market 26

Table 3 2 Criteria for evaluating the quality of cleaning the surface of the shield 37

Table 3 3 Alternatives affecting the quality of cleaning the surface of the shield 37

Table 3 4 Pairwise Comparison Matrix of criteria 39

Table 3 5 Normalised Pairwise Comparison Matrix of criteria 39

Table 3 6 Pairwise Comparison Matrix of alternatives according to Surface Roughness 40

Table 3 7 Normalised Pairwise Comparison Matrix of alternatives according to Surface Roughness 41

Table 3 8 Pairwise Comparison Matrix of alternatives according to Initial Condition of the Surface 42

Table 3 9 Normalised Pairwise Comparison Matrix of alternatives according to Initial Condition of the surface 42

Table 3 10 Pairwise Comparison Matrix of alternatives according to Degrees of Cleaning 43

Table 3 11 Normalised Pairwise Comparison Matrix of alternatives according to Degrees of Cleaning 44

Table 3 12 Alternative Weights of criterion 45

Table 3 13 Criteria Weights 45

Table 3 14 Alternative Score 46

Table 4 1 Reference table of risk levels 47

Table 4 2 Hierarchy of control over the secure implementation 49

Table 4 3 Compare the investment cost and risk cost of rotating shifts solution 50 Table 4 4 Compare the investment cost and risk cost of equipping headphones solution 52 Table 4 5 Levels of roughness according to quality standards for cleaning the surface

of the shield 62 Table 4 6 Some suggested hand symbols 63 Table 4 7 Cost effectiveness of the solution 3 68

LIST OF FIGURE

Figure 1 1 Logo of Vivablast (Vietnam) Co., Ltd 5

Figure 1 2 The organizational structure of Vivablast Co., Ltd 7

Figure 1 3 High-pressure water jetting process and final product at First Solar's production department 9

Figure 2 1 The internal steel structure is broken during traditional hand drilling 11

Figure 2 2 The internal steel structure is preserved when performing high-pressure water jetting 11

Figure 2 3 The high-pressure water jetting system 12

Figure 2 4 Cleaning quality of Class C surfaces at each level 15

Figure 2 5 General structure of the hierarchy 17

Figure 3 1 Fishbone diagram of the quality of cleaning the surface of the shield 21

Figure 3 2 A rusted surface after UHP cleaning (left) compared with standard surface water jetting type WJ1 (right) 22

Figure 3 3 Certificate of Hughes' high-pressure water jetting technique 23

Figure 3 4 A basic theoretical training class on water jetting techniques at Vivablast training center – Binh Chieu construction site 24

Figure 3 5 Occupational safety card of a water-jetting technician 24

Figure 3 6 Vivablast’s high-pressure water jetting machine 25

Figure 3 7 Some accessories come with the high-pressure water jetting machine 25

Figure 3 8 Position of the nozzle on the gun and its rotation amplitude 27

Figure 3 9 A water jetting machine and its accessories are being transported to another site 27

Figure 3 10 Standard performance posture 28

Figure 3 11 A TBM (Tool Box Meeting) at the beginning of a shift 29

Figure 3 12 Some risks of occupational accidents during high-pressure water jetting 30 Figure 3 13 Limited area of high-pressure water jetting at Binh Chieu construction site

31 Figure 3 14 A Standard Personal Protective Equipment model when performing high-pressure water jetting 31 Figure 3 15 Safety information boards in the high-pressure water jetting area 32 Figure 3 16 Emergency first aid supplies and fire extinguishers in the high-pressure water jetting area 32 Figure 3 17 Two waste water tanks at Binh Chieu construction site 33 Figure 3 18 Process of mixing abrasive particles into the high-pressure water stream 34 Figure 3 19 The surface of the shield (level WJ2) is scratched by large abrasive particles 34 Figure 3 20 Cost structure of a typical high-pressure water jetting system 35 Figure 3 21 The AHP hierarchical structure for the quality of cleaning the surface of the shield 38

Figure 4 1 Hearos 5826 Xtreme Protection Series UF Foam Ear Plugs (NRR 33) 48 Figure 4 2 Peltor Sport Tactical 100 Electronic Hearing Protector, Ear Protection, NRR

22 dB 48 Figure 4 3 Maintenance workers are repairing a high-pressure water jetting machine at the Binh Chieu construction site 65

TABLE OF CONTENT COMMENTS OF ADVISOR I COMMENTS OF REVIEWER II ACKNOWLEDGEMENTS III LIST OF ABBREVIATION IV LIST OF TABLE V LIST OF FIGURE VII TABLE OF CONTENT IX

INTRODUCTION TO THE REPORT 1

1 Rationale: 1

2 Objectives: 2

3 Scope and object: 2

4 Research methodology: 3

4.1 Data collection: 3

4.2 Data analysis: 4

5 Structure of thesis: 4

CHAPTER 1: INTRODUCTION TO VIVABLAST (VIETNAM) 5

1.1 Introduction to Vivablast company - History of formation and development: 5

1.2 Business sector activities and markets of Vivablast company: 5

1.3 Vivablast organizational structure: 6

1.4 Vivablast's business performance in recent years: 7

1.5 Vivablast development orientation: 8

CHAPTER 2: LITERATURE REVIEW 10

2.1 Introduction to cleaning shields by high-pressure water jetting method: 10

2.1.1 Purpose of cleaning shields by high-pressure water jetting method: 10

2.1.2 The stages of the process of cleaning shields by high-pressure water jetting

method: 12

2.2 The quality of the cleaning shield: 13

2.2.1 The concept of quality: 13

2.2.2 The quality of the cleaning shield: 14

2.3 The fishbone diagram: 16

2.4 The Analytic Hierarchy Process (AHP) method: 16

2.4.1 Method introduction: 16

2.4.2 Steps of AHP method: 17

CHAPTER 3: REALITY OF THE QUALITY OF CLEANING THE SURFACE OF THE SHIELD BY HIGH-PRESSURE WATER JETTING METHOD AT VIVABLAST (VIETNAM) CO., LTD 21

3.1 The influence of human factors on the quality of cleaning the surface of the shield: 21

3.2 The influence of mechanical factors on the quality of cleaning the surface of the shield: 24

3.3 The influence of methodological factors on the quality of cleaning the surface of the shield: 27

3.4 The influence of material factors on the quality of cleaning the surface of the shield: 32

3.5 The influence of financial factors on the quality of cleaning the surface of the shield: 35

3.6 Analytic Hierarchy Process (AHP) for the quality of cleaning the surface of the shield: 36

CHAPTER 4: SOLUTIONS TO IMPROVE THE QUALITY OF CLEANING THE SURFACE OF THE SHIELD BY HIGH-PRESSURE WATER JETTING METHOD AT VIVABLAST (VIETNAM) CO., LTD 47

4.1 Solution 1: Improving safety procedure: 47

4.1.1 Content of solution 1: 47

4.1.2 Comment on solution 1: 48

4.2 Solution 2: Completing the method of cleaning the shield according to ISO 9001:2015: 52

4.2.1 The basis of the solution: 52

4.2.2 Content of solution 2: 61

4.2.3 Comment on solution 2: 64

4.3 Solution 3: Improving equipment maintenance method: 64

4.3.1 Content of solution 3: 64

4.3.2 Comment on solution 3: 66

CONCLUSION 69

REFERENCES 70

APPENDIX 73

INTRODUCTION TO THE REPORT

1 Rationale:

Today, with the economy on a strong development momentum, Vietnam is likened to a large factory in Southeast Asia According to the General Statistics Office team (2022), Foreign Direct Investment (FDI) in Vietnam in the first three months of

2022 is expected to reach US $4.42 billion, up 7.8% over the same period last year In particular, foreign direct investment in the manufacturing industry reached 2.8 billion USD, accounting for 68.6% of newly and additionally registered capital The above data partly shows that the manufacturing industry in Vietnam will have a lot of potential for development in the future, and the number of machines and equipment for production needs will be more Besides, the need for maintenance of machinery and equipment (especially with metal structures) under the influence of temperature, humidity, and light

is also higher than before One of the solutions for the above is to implement corrosion measures directly on the surface of the equipment In addition, Vietnam has a tropical monsoon and hot and humid environment, where the air contains a high concentration of Cl ions, the average humidity is over 70%, the temperature variation between day and night is high, and ultraviolet radiation is high (at a very high level (above 7)), strong winds and annual tropical storms hit the 3,260 km coastline All of the above factors turn Vietnam into a place with a harsh climate environment and make general manufacturing materials (metal, concrete, etc.) surface stains, metal corrosion, temperature cracks, thermal radiation breaking chemical bonds in material structures, etc Therefore, the need for anti-corrosion in Vietnam is higher than in other regions and becomes more urgent than ever

anti-Vivablast (Vietnam) Co., Ltd is one of the leading units in Vietnam in the field

of anti-corrosion Vivablast offers anti-corrosion services according to international standards and tailored to the specific needs of the customer With 25 years of experience

in this field, Vivablast has implemented 10 different anti-corrosion solutions such as wrapping protection, passive fire protection, surface preparation, chemical cleaning, water proofing solutions, thermal spray coatings, protective and marine coating, high-pressure water jetting, CO2 dry ice cleaning, industrial flooring system In particular,

the solution of cleaning shields by the high-pressure water jetting method is the most commonly used

During the study of the current state of the high-pressure water jetting process at Vivablast, three issues need to be considered Firstly, the implementation of occupational safety is not good Secondly, the maintenance of the water jetting machine

is not consistent with the actual requirements Thirdly, there is no consensus on quality standards and quality inspection procedures

With all the above reasons plus the actual time having access to the high-pressure water jetting process at the company, I chose the topic Improving the quality of cleaning the surface of the shield by high-pressure water jetting method at Vivablast (Vietnam) Co., Ltd to do the graduation thesis report in the first semester of this academic year 2022-2023

2 Objectives:

Analyzing the quality of cleaning the surface of the shield by high-pressure water jetting method at Vivablast (Vietnam) Co., Ltd Detail:

Analysis of factors affecting the quality of cleaning the surface of the shield

Of the factors just analyzed above, find out which factors that affect the quality

of cleaning the surface of the shield the most

Proposing solutions to improve the quality of cleaning the surface of the shield by pressure water jetting method at Vivablast (Vietnam) Co., Ltd Detail:

high-Propose solutions for the factors that have the most influence on the quality of cleaning the surface of the shield

Each solution needs to be proven effective in practice by solution cost, expected results, implementation time, etc

3 Scope and object:

Research object: The quality of cleaning the surface of the shield by pressure water jetting method at Vivablast (Vietnam) Co., Ltd

high-Space: The main research topic is at Binh Chieu construction site - Vivablast

(Vietnam) Co., Ltd., address: Lot B1, Road No 2, Binh Chieu, Thu Duc city; and some other construction sites such as: Vung Tau, Ca Mau, Ben Tre, Quang Nam

Time: Data is provided for the last 3 years of Vivablast company (2020, 2021, and 2022)

Secondary data is collected from:

General Statistics Office of Vietnam: used to get the data for the Introduction to the report

Specialized documents on the method of high-pressure water jetting: These documents are mainly used for the analysis of the quality of cleaning shields in chapter 3 They are also used as a reference for chapters 2 and 4 For example, document Jetstream (2015) is used to describe the construction of a water jetting machine or document Joint Surface Preparation Standard (2017) is the most popular document used for the NACE certification exam (the author used it as a reference for the quality of cleaning the surface of the shield by high-pressure water jetting method)

Internal documents of Vivablast company: The most frequently used internal document in this thesis is the Method Statement: Shields cleaning by Bui Anh Quoc Along with internal documents of some other departments

A number of other related documents are listed in detail in the references section It is necessary to mention The Analytical Hierarchy Process by Saaty (1980) - which is the theoretical basis for applying the AHP method in

determining which factors have the most influence on the quality of cleaning the surface of the shield by high-pressure water jetting method

4.2 Data analysis:

As mentioned above, the data after being obtained from the expert will be preliminarily processed and then used the AHP method for calculation This is not a new method, but it is effective in ranking the importance of factors Especially in this thesis, the number of selection criteria and options is small, so it is easy to build the matrix and calculate the consistency In this thesis, the author uses the AHP tool through 8 steps of analysis including:

Step 1: Define criteria and alternatives

Step 2: Building the AHP hierarchical structure

Step 3: Survey and collect expert opinions in the company about the priority of the above factors

Step 4: Design the Pairwise Comparison Matrix of criteria

Step 5: Calculate the weights

Step 6: Check the consistency

Step 7: Repeat steps 3, 4, 5, and 6 with alternatives according to each criterion Step 8: Summarize the result

5 Structure of thesis:

In addition to the introduction to the report, comments of the advisor, comments

of reviewer, acknowledgements, list of abbreviation, list of table, list of figure, table of content, conclusion, references and appendix, the main content of the thesis consists of

4 chapters:

Chapter 1: Introduction to Vivablast (Vietnam) Co., Ltd

Chapter 2: Literature review

Chapter 3: Reality of the quality of cleaning the surface of the shield by pressure water jetting method at Vivablast (Vietnam) Co., Ltd

high-Chapter 4: Solutions to improve the quality of cleaning the surface of the shield

by high-pressure water jetting method at Vivablast (Vietnam) Co., Ltd

CHAPTER 1: INTRODUCTION TO VIVABLAST (VIETNAM)

1.1 Introduction to Vivablast company - History of formation and development:

Figure 1 1 Logo of Vivablast (Vietnam) Co., Ltd

Source: The Vivablast team (2019) Vivablast (Vietnam) Co., Ltd was founded in 1994 with 100% foreign capital Over the past 20 years, Vivablast has become a reliable partner in providing industrial asset protection services to clients such as PIRIOU, JGCS, Technip, KNOC, Metacor, PTSC Group, Vietsovpetro, etc In particular, Vivablast uses an innovative system of mobile blasting and painting to serve large projects such as Vietnam’s first refinery project – Dung Quat followed by Vung Ang Power Plant project, and the biggest Oil & Gas complex in Vietnam – Nghi Son Refinery In 2014, Vivablast expanded its business

to Thailand, Myanmar, and Malaysia

1.2 Business sector activities and markets of Vivablast company:

Basically, Vivablast's main business sector activity is industrial assets protection services Specifically, Vivablast provides solutions such as Access Solution, Protection Solution, Anti-Corrosion Solution, Insulation Solution, Fabrication Solution, and Mechanical Solution In addition, Vivablast is also the exclusive material distributor of Belzona (the world's leading polymer material manufacturer) in Vietnam

Currently, Vivablast's main market is still in Vietnam In addition, the company also provides the above service packages to other countries in Southeast Asia such as Laos, Cambodia, Thailand, Malaysia, and Myanmar

1.3 Vivablast organizational structure:

Regarding the personnel structure, the BOM (Board of Managers) consists of 5 members:

Mr Jacques Vivarès – President of the Company

Mr Boris Vivarès – Commercial and Business Development Director Shanthamani Muthukumar – Director of Vivablast Vietnam

Dang Xuan Dieu – Commercial Manager

Tran Thi Cam Tu – Financial Manager

The company is organized into 9 departments in charge of different functions and tasks The commercial department is responsible for bringing projects to the company and building relationships with partners The estimation department is responsible for calculating the number of materials needed for the project and reporting to the purchasing department The operation department is responsible for coordinating personnel and projects The QA/QC department is responsible for the quality of the project according to the agreed requirements between Vivablast and customers The HSE department is responsible for ensuring labor safety and waste treatment in projects The maintenance department is responsible for planning maintenance and performing repairs to the company's machinery The ADM/HR department is responsible for personnel management, recruitment, and dispatch of workers according to the requirements of the operation department The accounting department is under the direct management of Mrs Tu in terms of staff salaries, project costs, etc The purchasing department is also under the direct management of Mrs Tu and is responsible for planning purchase materials after receiving the quotation from the accounting department In addition, the purchasing department is also responsible for the import and export of goods to other countries

In addition, according to the data of the human resources department, the whole company has a total of 465 employees In more detail, the company has 35 management personnel and 370 technicians and operators

Figure 1 2 The organizational structure of Vivablast Co., Ltd

Source: The Vivablast team (2019)

1.4 Vivablast's business performance in recent years:

With more than 20 years of experience in the field of industrial asset protection services, in the past 5 years (from 2018 to 2022), Vivablast has continued to use those valuable experiences to implement many projects in the oil and gas industry, manufacturing industry, shipbuilding industry, thermal power industry, and renewable electricity industry As follows:

Oil & Gas Industry: Vivablast provides Refinery Construction and Maintenance, Offshore Platform Cleaning Work, Flare Bloom and Platform Construction, and Structure Repair Some typical projects can be mentioned, such

as the Aluminum insulation paint project in Thailand (2019-2020), the offshore drilling rig cleaning project in Vietnam (2020), etc

Manufacturing industry: Vivablast provides services for large construction projects These can be mentioned as Blasting & Protective Coating

(Shop & Field), Thermal Spray Coating, Passive Fire Proofing, Spray-on Insulation, Industrial Flooring Systems, Waterproofing, and Flexible & Conventional Insulation Some typical projects can be mentioned, such as the Port equipment maintenance project in Vietnam (2018-2020), the fertilizer plant maintenance project (2018-2019), etc

Shipbuilding: Vivablast is known as the number one contractor in the field

of marine corrosion protection for small and medium-sized ships over 6,000T that use services such as HP/UHP water jetting, Hulls Anti-Corrosion and Anti-Fouling Protection, floor coating, Tank Internal Lining, Thermal Spray Coating, etc Some typical projects can be mentioned, such as Trawler Ship project (2018), Deck and 94m Catamaran project, etc

Power Generation: In this industry, Vivablast provides several services such as Cooling Water Piping Lining, Tank Lining, Ceramic Coating Refurbishment, Heat Exchanger Cleaning, etc Two typical projects in this industry that Vivablast did are Power Plant Maintenance Project, and Power Plant Construction Project

1.5 Vivablast development orientation:

From 2014 until now, Vivablast has made strategic changes when expanding its business to Thailand, Myanmar, and Malaysia with the main areas of wind and solar power, also known collectively as renewable electricity With available methods and experiences for more than 20 years, Vivablast is implementing a series of main projects today, such as the blade repair project in Thailand wind farm (2022), the rooftop solar panel installation project (2022), the project of supplying and installing solar panels at

a dragon fruit farm in Vietnam (2021-2023)

In wind power projects, Vivablast uses the Rope Access Method and Blade Access Platform to access the turbine blades When approaching turbine blades, workers will perform blade maintenance (usually using anti-corrosion paint) With some key projects such as in Taiwan and Thailand, Vivablast also uses specialized drones to survey the entire wind farm

In the solar industry, Vivablast provides maintenance and cleaning services for

solar panels In addition, Vivablast also provides shield cleaning services to First Solar customers In particular, the high-pressure water jetting is an extremely important step when implementing this project These shields, after being cleaned, will be the main supporting parts in First Solar's solar cell production It is also noticeable that the current high-pressure water jet cleaning process is also one of Vivablast's pioneering service solutions for further breakthrough developments in the renewable electricity industry in the future

Figure 1 3 High-pressure water jetting process and final product at First Solar's

production department

Source: Muthukumar (2019)

CHAPTER 2: LITERATURE REVIEW

2.1 Introduction to cleaning shields by high-pressure water jetting method:

2.1.1 Purpose of cleaning shields by high-pressure water jetting method:

The high-pressure water jetting method was known as a traditional surface cleaning method of Vivablast for over 20 years According to the Vivablast team (2019), this method uses two types of high pressure (10,000 PSI) and ultra-high pressure (36,500 PSI) to remove rust, varnish, drill mud on the surface of the shield depending on the customer's requirements (refer to item protection solutions – HP/UHP Jetting) More specifically, Vivablast now uses high-pressure water jetting to clean the surfaces of ship hulls, voids, ballast tanks, loading ramps, pilings; concrete cutting and surface preparation; rust removal, oil painting, drilling mud in pipe yards; Clean surfaces in gas plants, pressurized water pipes, lead coatings To see the advantage of the high-pressure water jetting method over other traditional cleaning methods, Figures 2.1 and 2.2 will show the difference According to Conjet (2021), breaking the concrete layer by the traditional hand drilling method has a very high probability of breaking the structure of the steel inside On the opposite, the high-pressure water jetting method not only does not break this steel structure layer but also gives greater efficiency and safety for workers On the one hand, the method of high-pressure water splashing proves to be less harmful to the working environment On the other hand, it helps workers - who are in direct contact with the source of vibrations to avoid Hand-arm vibration (Rebecca & Elizabeth, 2005)

Figure 2 1 The internal steel structure is broken during traditional hand drilling

Source: Conjet (2021)

Figure 2 2 The internal steel structure is preserved when performing high-pressure

water jetting

Source: Conjet (2021) According to the Jetstream team (2015), the high-pressure water jetting system

is normally divided into two main parts: the water pump and the water gun (Figure 2.3)

In addition, the system has several important accessories such as a high-pressure hose, pressure regulating valve, safety valve, nozzle (Straight, forward, reverse nozzle), flexible lance, foot valve, and rigid lance Regarding the operating principle of the system, a high-pressure motor will take water from a low-pressure place and pump it

through a one-way valve system to increase water pressure and direct it to the worker's gun When the user pulls the trigger, the water will be shot out into the jet by the high-pressure nozzle When the user releases the trigger, the water will return to the old water area

Figure 2 3 The high-pressure water jetting system

Source: The Jetstream team (2015)

2.1.2 The stages of the process of cleaning shields by high-pressure water jetting method:

According to Quoc (2021), the process of cleaning shields by high-pressure water jetting method goes through 4 stages:

Stage 1 (Preparation): The main task in this stage is preparing the basic requirements before performing the main stage Among them, the surface preparation work is the most important A correct determination of the initial condition of the shield's surface combined with the customer's requirement will result in a suitable surface standard for high-pressure water jetting (Refer to section 2.2 – The quality of cleaning the surface of the shield) In addition, some other preparation work is equally important, such as determining the number of shields delivered by the customer; determining the number of abrasive particles, the amount of packaging, and machine oil; preparing a water jetting machine, a packing machine, a heat gun, and some other supporting tools

Stage 2 (High-pressure water jetting): This is the most important stage of the whole process This stage was introduced in section 2.1.1

Stage 3 (Heating): This is the treatment process after high-pressure water jetting is done Workers use a heat gun to provide heat in the form of a stream of air with a temperature of up to 600 degrees Celsius directly on the surface of the shield to evaporate the remaining water stains

Stage 4 (Packing): The final stage of the high-pressure water jetting process uses a vacuum machine to pack the entire shields In addition to the aesthetics of the product when delivered to the customer, the purpose of the packaging is to prevent the air from coming into direct contact with the surface after the water jetting, because the air will quickly oxidize the surface of the shields

2.2 The quality of the cleaning shield:

2.2.1 The concept of quality:

There are many different concepts of quality in the world With different fields and different purposes, the perspective on quality is also different But there is only one internationally accepted definition, that of the International Organization for Standardization (ISO) According to Hoyle (2015), clause 3.6.2 states that: Quality degree to which a set of inherent characteristics of an object fulfills requirement Where:

Characteristics: Can be physical (mechanical, electrical, chemical, or biological characteristics); sensory (related to smell, touch, taste, sight, hearing); behavioral (courtesy, honesty, veracity); temporal (punctuality, reliability, availability, continuity); ergonomic (physiological characteristic, or related to human safety); functional (maximum speed of an aircraft)

Objects can be material (an engine, a sheet of paper, a diamond), material (conversion ratio, a project plan), or imagined (the future state of the organization)

non-Requirements can be need or expectation that is stated, generally implied,

or obligatory

2.2.2 The quality of the cleaning shield:

If explained according to the concept of quality of the International Organization for Standardization (ISO) above, the quality of cleaning the surface of the shield by high-pressure water jetting is The degree to which a set of three characteristics of the shield fulfills two requirements Detail:

Characteristics (Refer to the Method Statement: Shields cleaning (2021) by Bui Anh Quoc):

Ra (average roughness): measures the deviation of a surface from a mean height Measured in µm

Rz is the average height of the profile Measured in µm

L: Standard length Measured in mm

Objects: The shield (usually made of steel)

Requirements (Refer to Joint Surface Preparation Standard (2017) by the Society for Protective Coatings/NACE International): The quality of the shield is composed of two main factors: The initial condition of the surface before cleaning and the Degrees of cleaning There are 8 initial conditions of the surface before cleaning (Refer to appendix A) There are also 4 degrees of cleaning:

WJ-1: Clean to bare substrate

WJ-2: Very thorough or substantial cleaning

Table 2 1 Quality standards for cleaning the surface of the shields

Source: The Society for Protective Coatings/NACE International (2001) For example, for a surface with an initial condition of class C, there are 4 surface quality standards after cleaning: C WJ-1, C WJ-2, C WJ-3, and C WJ-4

Figure 2 4 Cleaning quality of Class C surfaces at each level

Source: The Society for Protective Coatings/NACE International (2001)

2.3 The fishbone diagram:

Known as one of the seven basic tools of quality in the early 1960s, the Ishikawa diagram is a method to identify problems and provide solutions in management and leadership According to Ishikawa (1968), this diagram is shaped like a fishbone and is used to show factors about people, machines, working environment, materials, methods, ways of measuring, etc All of them can cause problems that need to be fixed From these major factors, we find other, smaller factors that may be responsible for the undesired results This tool has several advantages such as: being highly intuitive; can find a single root cause found multiple times; observe all causes at once However, this tool also has some disadvantages such as many causes that can be difficult to understand when looking at the diagram, and difficulty to determine the relationship between causes With the consent of Vivablast experts, the author uses a fishbone diagram to analyze the root causes affecting the quality of cleaning the surface of the shield In that diagram (refer to figure 3.1), 5 main factors are included in the analysis: Man, Machine, Method, Material, and Money

2.4 The Analytic Hierarchy Process (AHP) method:

2.4.1 Method introduction:

AHP is a multi-objective decision-making method developed by Thomas L.Saaty (an Iraqi mathematician) in 1980 This method allows us to quantify, sort and select an alternative that meets the previously specified criteria By comparing pairs of criteria as well as pairs of methods within each criterion, AHP can assist to select the optimal solution that meets the decision maker's criteria

It is noticeable that the factors must ensure uniformity and reversible comparison conditions (For example, if factor A is n times more important than factor B, then factor

B is 1/n times more important than factor A) before being included in the analysis

Suppose someone needs to decide for a situation, let's say a goal In order to achieve that goal, it is necessary to rely on several criteria and options It can be described by the diagram below:

Figure 2 5 General structure of the hierarchy

Source: Saaty et al (1980)

2.4.2 Steps of AHP method:

According to Saaty et al (1980), the steps to implement the Analysis Hierarchical Process method (AHP) are as follows:

Step 1: Determine priority for criteria:

Set up a square matrix of order n (n is the number of criteria to consider) The data in the table is denoted by aij (with i in rows, and j in columns) Priority by each pair

of criteria is determined by positive integer values from 1 to 9 or the reciprocal of these numbers (Refer to appendix B – Main part) For each pair of criteria, it is necessary to enter two preferred values in the table, a positive integer value and an inverse value It

is noticeable that the value of cells with the same row and column is “1”

Look at table 2.2, for example criterion 1 has a12 times the value of criterion 2

First, it is necessary to enter the value of “a12” in the cell with row 1 and column 2 Then enter the value of “1/a12” in the cell with row 2 and column 1

Table 2 2 Traditional AHP pairwise comparison matrix

Step 2: Calculate the weights for criteria:

Based on table A, replace those aij values by dividing aij by the sum of the values

in the respective column The average of the values across each row will be the weight

of each criterion C1, C2, C3, , Cn The result will have the following new matrix table:

Table 2 3 Normalised Pairwise Comparison Matrix

𝑛 𝑖=1

𝑛 , with j∈ {1, 𝑛} (2) However, before a conclusion can be drawn, consistency in expert judgment must be

ensured throughout the application of the method The consistency ratio (CR) is determined as follows:

λmax = ∑𝑛𝑖=1𝑤𝑖*∑𝑛𝑗=1𝑎𝑖𝑗 (5)

n is the number of elements to be compared in pairs in one computation, which is the size of the calculation matrix

RI (random index) is determined by the given table:

Table 2 4 The random index corresponds to the number of selection criteria

considered

n 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

RI 0 0 0.58 0.9 1.12 1.24 1.32 1.41 1.45 1.49 1.51 1.54 1.56 1.57 1.59

Source: Saaty et al (1980)

In all cases, the CR should not be greater than 10% For 3x3 matrices, CR needs to be

no larger than 5%, and the corresponding value for 4x4 matrices is 9% If the CR is greater than the above-mentioned levels, there is an inconsistency in the expert judgment, and it is necessary to re-evaluate and recalculate

Step 3: Calculating the priority of the alternatives according to each criterion:

In this step, the performer calculates for each criterion, the calculation method is the same as in Step 1 and Step 2 However, the data included in the evaluation is the result of the comparison of the priority of the alternatives considered according to each criterion Thus, the evaluator has to perform n matrices for n different criteria As a result, there will be n matrices of 1 column m rows Consistency ratio checking should also be performed to ensure that the results obtained have adequate confidence

Step 4: Scoring for alternatives and selection:

This is the final step in the process of evaluating and choosing alternatives The performer concatenates the n 1-column m-row matrices (in Step 3) into the m-row n-column matrix Multiplying that matrix by 1 column n rows (the result of Step 2) As a result, there is a matrix of m rows 1 column The resulting matrix will indicate the best option to choose is the one with the highest result value

CHAPTER 3: REALITY OF THE QUALITY OF CLEANING THE SURFACE

OF THE SHIELD BY HIGH-PRESSURE WATER JETTING METHOD AT

VIVABLAST (VIETNAM) CO., LTD

The author analyzes the quality of cleaning the surface of the shield by high-pressure water jetting method at Vivablast (vietnam) co., Ltd through the Ishikawa method These

are summarized by the fishbone diagram below:

Figure 3 1 Fishbone diagram of the quality of cleaning the surface of the shield

Source: Author's own compilation This diagram shows an overview of the five factors that affect the quality of cleaning the surface of the shield These can be mentioned as Man, Method, Material, Machine, and Money Each factor has three detailed items that have a direct impact on the quality of cleaning the surface of the shield (detailed in chapter 3)

3.1 The influence of human factors on the quality of cleaning the surface of the shield:

The project manager plays a key role in the overall success of the project They

have an important influence on the quality of the cleaning shield In particular, the faster oxidation of the surface of the shield after water jetting is a common risk of the high-pressure water jetting method (Figure 3.2) Project managers can limit this risk by packaging the product after cleaning to prevent the surface of the shield from being exposed to the air The project manager needs to coordinate with the warehouse department to organize the delivery of goods to the customer and the acceptance of the shipment as soon as possible This is being done well in Vivablast On the other hand, personnel coordination is a prominent issue at Vivablast Because Vivablast is a company specializing in providing industrial services at other construction sites, workers are often dispatched to projects far away, even abroad such as Laos, Thailand, and Malaysia Therefore, the arrangement of personnel to move as well as train the high-pressure water jetting technique for each project not only takes time but also directly affects the surface quality of the shield (in the case of the newbies who don't know how

to do it) In this problem, Vivablast is doing quite well because they have dedicated engineers in charge of the project directly at each site

Figure 3 2 A rusted surface after UHP cleaning (left) compared with standard surface

water jetting type WJ1 (right)

Source: Lydia (2019) The supervisor is the person who supervises the implementation of the plan under the direction of management Other duties of the supervisor are checking the number of inputs and outputs, checking the surface quality, and reporting daily progress to the project manager Along with the specialized engineer, the supervisor is the person who understands the common errors on the surface of the structure when splashing water

such as rust, blistering, and rapid oxidation At Vivablast today, engineers and supervisors before participating in each project are trained in the basic certificate of Hughes' high-pressure water jetting technique (Figure 3.3)

Figure 3 3 Certificate of Hughes' high-pressure water jetting technique

Source: Hoa (2009) The third group of personnel that has a direct influence on the quality of cleaning the surface of the shield is the workers They are the ones who receive direct instructions from supervisors and engineers to perform tasks such as surface preparation, cleaning, packaging, and delivery One of the common problems among workers is salary If they

do not receive a remuneration suitable to the nature of the job, they will not have the best mentality to work They will even be lazy or deliberately make it through the speakers This leads to poor quality of cleaning the shield, which entails the need to re-spray water and slow down the project's progress In this regard, Vivablast currently provides additional support for workers and allows them to participate in full insurance according to the Vietnamese government's decree No 58/2020/ND-CP regulations on the management of the collection of social insurance and health insurance (issued on May 27, 2020) In terms of capacity, Vivablast's workers receive basic training in high-pressure water jetting techniques at the training center in Binh Chieu headquarters (Figure 3.4) as well as training in safety certifications (Figure 3.5)

Figure 3 4 A basic theoretical training class on water jetting techniques at Vivablast

training center – Binh Chieu construction site

Source: The Vivablast team (2019)

Figure 3 5 Occupational safety card of a water-jetting technician

Figure 3 6 Vivablast’s high-pressure water jetting machine

Source: The Vivablast team (2021)

Figure 3 7 Some accessories come with the high-pressure water jetting machine

Source: The Jetstream team (2015) Included with the high-pressure water jetting machine are some important accessories such as a gun, a nozzle, a safety valve, a hose, etc (Figure 3.7) On the market today, there are 7 common types of high-pressure water jetting machines (Table 3.1) With more than 20 years of experience in the field of water jetting combined with

customers' cleaning requirements, Vivablast chose the BHP/120053E series pressure type from 1,200 bar to 17,405 bar) for the project

(high-Table 3 1 Popular types of water jetting machines on the Vietnamese market

Source: The Bhartiya team (2017) From the perspective of the quality of cleaning the shield, the BHP/120053E water jetting machine is in line with current project standards such as:

The water jetting pressure is suitable for cleaning level WJ-1

Customers require that the surface of the shield after high-pressure water jetting must comply with C WJ-1 standards

Vivablast has full tools at Binh Chieu's main construction site to do the maintenance

If the high-pressure water jetting is not regularly maintained, it will affect the quality of cleaning the surface of the shield such as:

The damaged nozzle causes the adjustment of the water ejection force to be uneven, leading to the fracture of the internal structure of the shield (in case the pressure is too high) (Figure 3.8)

The pressure pump valve does not work properly (irregular pumping), resulting

in irregular high-pressure water injection As a result, the surface of the shield has some clean places, and some places it does not

The machine is damaged locally to the point of being unusable For example,

when worker A just shot 2/3 of the surface of the shield with high-pressure water, the machine broke down So the shield could not be packed As a result, 2/3 of that surface will be in direct contact with the air more and more susceptible to corrosion

Figure 3 8 Position of the nozzle on the gun and its rotation amplitude

Source: The Jetstream team (2015)

In addition, because the number of Vivablast's water jetting machines is limited, this machine is often transported back and forth between construction sites (Vung Tau site, Dong Nai) Frequent movement not only increases the risk of machine failure but also affects the quality of cleaning the shield

Figure 3 9 A water jetting machine and its accessories are being transported to another

site

Source: Author's own compilation

3.3 The influence of methodological factors on the quality of cleaning the surface

of the shield:

The water jetting technique of the skilled worker has a direct influence on the quality of cleaning components Depending on the requirements of firing pressure and firing position, skilled workers need to perform manually, semi-automatically (manually with the assistance of assistive devices) or fully automated by machines Currently, Vivablast is applying high-pressure water jetting in 2 ways: manual and semi-automatic

In particular, the most important thing in the high-pressure water jetting technique is the resistance of the gun to the reverse thrust of the gun when spraying This force has a value of F' = 50 lb (23 kg), which is 1/3 of the average weight of the worker In this case, the technician's standard posture is that they have to stretch The technician used his legs

to fix the shooting position and slightly shifted his body weight forward to counteract the reverse thrust of the gun (Figure 3.10) When higher pressure is required (the back thrust of the gun is more than 23kg), the semi-automatic method is used This method requires some special equipment to assist the technician

Figure 3 10 Standard performance posture

Source: The Vivablast team (2021) Reality shows that Vivablast's waterjet technicians perform the work under the direct supervision of engineers and supervisors If the quality of cleaning the surface of the shield is not good, the technician will be prompted immediately to correct the