The application process of fusion-bonded epoxy as field joint ...

The application process of fusion-bonded epoxy

as field joint coating

Geert Jan Kap

Faculty of Mechanical, Maritime and Materials Engineering

Faculty of Civil Engineering and Geosciences

Faculty of Technology, Policy and Management

Delft University of Technology

Allseas Engineering BV

Thesis

Master of Science - Transport, Infrastructure and Logistics

August 2013

Preface

This report marks the final steps towards my graduation. It describes my thesis

work, which I completed at Allseas Engineering BV in corporation with Delft

Technical University. During this masters thesis I enjoyed the combination of

scientific knowledge with hands on experimenting. One day I would be reading

about the chemical cross linking of thermosetting polymers. The next day I would

build a machine and clean the excess epoxy powder out of a fluidised bed with a

shop vac. To me this is the definition of being a true engineer.

A wise man once said: when thanking people you should mention everybody or

nobody at all. True words, but with the risk of forgetting a couple I will give it

a try. First off I would like to thank my graduation committee for their support,

comments and guidance throughout the process. Professor Rijsenbrij for his enthu-

siasm on the subject. Wouter van den Bos for helping me stay on topic. Professor

Heijnen for her help with getting my thoughts on paper. Kirill and Erik, for their

vast knowledge and discussions on the topic of field joint coating. Manuel, Jos,

Mark, Warner and everybody else from PPD and the yard in IJmuiden for their

support during the tests. My roommates in C3.27 and the colleagues I shared a

pool-car with or shared a small break with by the coffee machine. My parents

Aaldrik and Marianne, my family and my parents-in-law Wolter and Arina for

their never ending support. My close friends for the good times we had besides

our studies and Arne in particular for his tips on writing the final report.

I would like to thank Allseas for the chance they gave me to do my thesis work

at their exciting company. I am grateful for the chances given and I am looking

forward to continue my career within the company.

Finally I would like to thank my lovely girlfriend Fenna for sticking by my side

for all these years and especially these final weeks. Your love and support were of

great significance for the completion of this thesis and the successful ending of my

career as a student.

Delft University of Technology

FACULTY MECHANICAL, MARITIME AND

MATERIALS ENGINEERING Department Marine and Transport Technology

Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl

This report consists of 99 pages. It may only be reproduced literally and as a whole. For commercial purposes only with written authorization of Delft University of Technology. Requests for consult are only taken into consideration under the condition that the applicant denies all legal rights on liabilities concerning the contents of the advice.

Specialization: Transport Infrastructure and Logistics Report number: 2013.TIL.7786 Title: The application process of fusion-

bonded epoxy as field joint coating

Author: G.J. Kap

Title (in Dutch) Het applicatie proces van fusion-bonded epoxy als field joint coating

Assignment: Master thesis

Confidential: yes

Initiator (university): Prof. ir. J.C. Rijsenbrij (Delft University of Technology)

Initiator (company): Dr. K. Kavelin, Ir. E. Kramer (Allseas Engineering BV, Delft)

Supervisor: ir. W. van den Bos, Dr.ir. P.W. Heijnen

Date: August 23, 2013

Student: G.J. Kap Assignment type: Master thesis

Supervisor (TUD): ir. W. van den Bos, Dr.ir.

P.W. Heijnen (TU Delft)

Creditpoints (EC): 30

Supervisor (Company) Dr. K. Kavelin, Ir. E.

Kramer (Allseas Engineering BV)

Specialization: TIL

Report number: 2013.TIL.7786

Confidential: Yes

Subject: The application process of fusion-bonded epoxy as field joint coating

Allseas is one of the leading offshore pipeline installation contractors in the business. For the

installation of pipes, it uses the so called S-lay method, a method where pipe sections, called joints,

are assembled into a continuous pipeline at the firing line, on-board the pipe lay vessel. Subsequent

stations perform welding, non-destructive testing and coating tasks in this firing line. Since the

founding of the company in 1985, much of the equipment to perform these tasks was designed,

developed and built in-house. A lot of effort was put into improving installation time. Allseas and its

clients mainly focused on the welding and NDT testing stations while the coating process drew

relatively less attention.

In recent years the attention of the clients of Allseas shifted to the coating stations. There were also

signals that on some projects the process time of individual coating stations negatively affected the

overall installation time. This has triggered Allseas to also improve the coating process, with a focus

on process times, while coating quality should not suffer. A combined machine for heating and coating

was used, a mechanical blaster was installed in the firing line and the grit blast equipment was scaled

up with the addition of more blast heads. Some of these improvements were more successful than

others.

The assignment of this master’s thesis is to make an analysis of the current coating process and find

possible improvements. These improvements should be tested on process times and coating quality.

Finally an advice should be given about the implementation of these improvements within the current

pipeline installation process.

The report should comply with the guidelines of the section. Details can be found on the website.

The professor,

Prof. ir. J.C. Rijsenbrij

Summary

Allseas is one of the leading offshore pipeline installation contractors in the busi-

ness. For the installation of pipes, it uses the so called S-lay method, a method

where pipe sections are assembled into a continuous pipeline at the firing line, on-

board the pipe lay vessel. Subsequent stations perform welding, non-destructive

testing and coating tasks in this firing line.

Since the founding of the company in 1985, much of the equipment to perform

these tasks was designed, developed and built in-house. A lot of effort was put

into improving installation time. Allseas and its clients were mainly focused on the

welding and NDT testing stations while the coating process drew relatively less

attention.

In recent years the attention is shifted to the coating stations. There were also sig-

nals that on some projects the process time of individual coating stations negatively

affected the overall installation time.

Although some effort was made in the past to improve the coating process the re-

sults were disappointing. The need for reducing overall process times while main-

taining coating quality still remains. Therefore Allseas initiated this research,

exploring possible changes to the coating process.

A preliminary research showed that fusion-bonded epoxy is the most used coating

type. Based on that the choice was made to focus the research on the application

process of fusion bonded epoxy.

The goal of the research was formulated as a research question: What are the

possibilities to change the current process of field joint coating application, in

order to achieve faster cycle times while maintaining the current coating quality,

while taking into account requirements for changes to the process?

To answer the research question the current process of pipeline production was

analysed. From this analysis it was concluded that there were three possibilities

for changes to the process:

• The order of steps within the process

• Combination of steps within the process

• Alternative methods within the process step

A research into the current cycle times showed that for some projects the field

joint coating stations could be critical. From the limited amount of data available

it could be seen that the most time was used at the station where the joint is

heated and coated. Analysis of cycle times did not show the surface preparation

station to be critical. Interviews with Allseas employees however confirmed that

for some projects the surface preparation station was critical.

The analysis of the current equipment used for the application process of fusion-

bonded epoxy was done. This research showed that the current method of surface

preparation, grit blasting, could be improved. The current method gives good

results, but due to a limitation in space for the grit handling units it is difficult to

optimise this method.

The method of heating the joint with induction heating is the most efficient and

clean way. The shape of the coil however could be changed in order to combine

the heating coil with other equipment.

A research into possible alternatives was done, based on the conclusions of the

analysis of the current process and equipment. A number of possible alternatives

were found.

The order of steps within the process:

• Pre-blasting with mechanical blasting followed by cleaning with laser or dry

ice

• Pre-blasting with grit blasting followed by cleaning with laser or dry ice

Combination of steps within the process:

• Shockwave Induced Spray Painting

• Combined Heat & Coat machine with alternative heating coil

Alternative methods within the process step:

• Dry ice with grit blasting instead of grit blasting

• Pick brush instead of grit blasting

• Low application temperature FBE instead of FBE

• Surface treatment with laser blasting instead of grit blasting

Based on found requirements for new equipment and the change of the process, a

number of these alternatives were chosen to further research:

• Pre-blasting with mechanical blasting followed by cleaning with laser or dry

ice




Practical tests were performed to see whether these possible alternatives could

lead to the reduction of cycle times while maintaining the coating quality. A test

setup was designed and built in-house. The test setup replicated the process in the

firing line. Steel plates were used, which were treated with the different surface

treatment methods. After that they were heated in an industrial oven. After

heating they were coated with FBE. Once the FBE was fully cured, destructive

tests were performed to evaluate the level of the quality of the coating.

During the tests different measurements were taken. The time each of the surface

treatment methods took was recorded. The noise levels of the surface treatment

were recorded as part of the safety aspect. During the destructive test the degra-

dation of the coating was measured.

Based on the test result it was concluded that there are three alternatives that can

be identified as prominent alternatives for FBE application:

• Pre-blasting with mechanical blasting followed by cleaning with laser

• Dry ice with grit blasting

• The application of LAT FBE

Based on the conclusions some further recommendations can be made for each of

the three possible alternatives.

Pre-blasting with mechanical blasting followed by cleaning with laser:

• Research the possibilities for the incorporation of a mechanical blaster in the

bevelling station

• Further test the use of laser equipment in the current process and with the

current equipment

• Investigate possible safety issues related to the use of laser equipment

Dry ice with grit blasting:

• Research the logistics of dry ice pellets

• Research the possibility of producing of dry ice on board the vessels

• Execute more tests with different types of blast media added to the dry ice

• Research the possibilities for the reduction of noise levels

• Investigate the possible safety issues with CO2

The application of LAT FBE:

• Research the possible time reduction when applying LAT FBE with current

equipment

• Research the cost aspect of applying LAT FBE powder with respect to the

reduction of time (cost versus gain)

Contents

Preface x

Summary x

List of Figures xi

List of Tables xv

Glossary xvii

1 Introduction 1

1.1 General introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Problem definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.3 Relevance of the research . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.4 Goal of research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.5 Structure of the report . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2 Analysis - process 13

2.1 Requirements for the pipeline production process . . . . . . . . . . . . . 13

2.2 Process description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.3 Cycle time analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3 Analysis - equipment 23

3.1 Requirements for equipment . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.2 Surface preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3 Coating application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

ix

CONTENTS

4 Alternative application methods 35

4.1 Process alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.2 Surface preparation alternatives . . . . . . . . . . . . . . . . . . . . . . . 39

4.3 Coating application alternatives . . . . . . . . . . . . . . . . . . . . . . . 45

4.4 Choice of alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5 Tests 49

5.1 Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.2 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

5.3 Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

5.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

6 Conclusions & Recommendations 73

6.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

6.2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Bibliography 77

x

List of Figures

1.1 S-lay method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Firing line on board PLV Solitaire . . . . . . . . . . . . . . . . . . . . . 4

1.3 Schematic overview of the firing line of the Solitaire . . . . . . . . . . . 5

1.4 Percentage of field joints per surface preparation method . . . . . . . . . 7

1.5 Percentage of field joints per coating type . . . . . . . . . . . . . . . . . 8

2.1 Scematic overview of the process . . . . . . . . . . . . . . . . . . . . . . 15

2.2 Process of pre-production . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.3 Example of a J-bevel and a K-bevel . . . . . . . . . . . . . . . . . . . . 17

2.4 Process of welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.5 Build-up of welds in the pipeline wall . . . . . . . . . . . . . . . . . . . . 18

2.6 Schematic process overview of Field Joint Coating . . . . . . . . . . . . 20

2.7 Typical field joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.1 Anchor profiles on substrate; left is shallow, right is deep[1] . . . . . . . 25

3.2 Sample of blast media: steel shot and grit mix . . . . . . . . . . . . . . 26

3.3 Grit blast frame in operation on the pipe . . . . . . . . . . . . . . . . . 27

3.4 Grit handling unit - LTC . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.5 Green mile of PLV Solitaire . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.6 Heating coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.7 Heat profile along the field joint[2] . . . . . . . . . . . . . . . . . . . . . 31

3.8 FBE coating frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.9 Inside of the coating ring of the application frame . . . . . . . . . . . . . 32

3.10 Fluidised bed together with control panel . . . . . . . . . . . . . . . . . 33

4.1 Pre-blast process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

xi

LIST OF FIGURES

4.2 FBE application dishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.3 Combined steps process for heat and coat machine . . . . . . . . . . . . 38

4.4 Contact blocks of heat and coat machine . . . . . . . . . . . . . . . . . . 38

4.5 Spacing between the heating coil and pipe . . . . . . . . . . . . . . . . . 39

4.6 Mechanical blasting machine [3] . . . . . . . . . . . . . . . . . . . . . . . 40

4.7 Bauhaus mechanical blaster in FL . . . . . . . . . . . . . . . . . . . . . 41

4.8 Surface preparation with laser beam . . . . . . . . . . . . . . . . . . . . 42

4.9 Laser treatment of steel piece . . . . . . . . . . . . . . . . . . . . . . . . 42

4.10 Pellets of dry ice used for blasting . . . . . . . . . . . . . . . . . . . . . 43

4.11 Principle of dry ice blasting [4] . . . . . . . . . . . . . . . . . . . . . . . 44

4.12 Power wire brush with hardend bent ends [5] . . . . . . . . . . . . . . . 44

4.13 Power wire brush frame . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

4.14 Schematic overview SISP process [6] . . . . . . . . . . . . . . . . . . . . 46

5.1 Test plates blasted and put outside . . . . . . . . . . . . . . . . . . . . . 51

5.2 Corroded test plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.3 Test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.4 Grit blast head fitted in test setup . . . . . . . . . . . . . . . . . . . . . 53

5.5 Test plates in industrial oven . . . . . . . . . . . . . . . . . . . . . . . . 54

5.6 FBE application nozzle fitted in test setup . . . . . . . . . . . . . . . . . 54

5.7 Mechanical blaster test setup . . . . . . . . . . . . . . . . . . . . . . . . 55

5.8 Simulating FL conditions with heat and NDT water . . . . . . . . . . . 56

5.9 Dry ice blasting method . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.10 Laser treatment test setup . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.11 Surface comparator with mechanical blasted test plate . . . . . . . . . . 60

5.12 Measuring of the Testex tape . . . . . . . . . . . . . . . . . . . . . . . . 61

5.13 Surface after mechanical blasting . . . . . . . . . . . . . . . . . . . . . . 62

5.14 Surface after laser blasting . . . . . . . . . . . . . . . . . . . . . . . . . . 62

5.15 Test setup Noise level measurement . . . . . . . . . . . . . . . . . . . . . 63

5.16 Cured coating on a test plate . . . . . . . . . . . . . . . . . . . . . . . . 64

5.17 Adhesion test - resistance to removal . . . . . . . . . . . . . . . . . . . . 65

5.18 Pull-off tester and 20mm dollies glued to test plate . . . . . . . . . . . . 66

5.19 Pull-off results 14mm: three failure types for batch D . . . . . . . . . . 68

xii

LIST OF FIGURES

5.20 Cathodic disbondment test setup at Element, Amsterdam . . . . . . . . 69

5.21 Cathodic disbondment on test plate . . . . . . . . . . . . . . . . . . . . 70

xiii

LIST OF FIGURES

xiv

List of Tables

2.1 Firing line stations overview . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2 Joint types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.3 Cycle times of the three main steps . . . . . . . . . . . . . . . . . . . . . 21

2.4 Cycle times per station . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5.1 Anchor profile measurements . . . . . . . . . . . . . . . . . . . . . . . . 61

5.2 Cycle time measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 63

5.3 Noise level measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 63

5.4 Dry film thickness measurements . . . . . . . . . . . . . . . . . . . . . . 64

5.5 20mm dolly pull-off test measurements . . . . . . . . . . . . . . . . . . . 67

5.6 14mm dolly pull-off test measurements . . . . . . . . . . . . . . . . . . . 67

5.7 Cathodic disbondment test results . . . . . . . . . . . . . . . . . . . . . 70

5.8 Test results summarised . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

6.1 Test results summarised . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

xv

LIST OF TABLES

xvi

Glossary

DJF Double Joint Factory

FBE Fusion-bonded Epoxy

FJ Field Joint

FJC Field Joint Coating

FL Firing Line

HSS Heat Shrink Sleeve

LE Liquid Epoxy

NDT Non-Destructive Testing

OD Outside Diameter

PLV Pipelay Vessel

PP Pipeline Production

PPD Pipeline Production Departement

PQT Procedure Qualification Trial

PWB Power Wire Brush

QHSE Quality, Health, Safety and Environment

WT Wall Thickness

xvii

LIST OF TABLES

xviii

1

Introduction

This chapter introduces the topic of this masters thesis. Section 1.1 will give a general

introduction of the topic. In section 1.2 the problem definition is stated. In section 1.3

the relevance of the research is stated. In section 1.4 the goal of the research is sketched.

Finally in section 1.5 the structure of the report is given.

1.1 General introduction

Around the world many offshore platforms extract hydrocarbons in the form of oil

and natural gas. One way to transport these hydrocarbons between platforms wells

and onshore is by means of pipelines. This method of transportation is a low cost

alternative with respect to tons per kilometre. Before transportation can commence

the pipeline needs to be produced and installed.

Allseas is a company that installs those pipelines. As a commercial company their

goal is to lay the best pipeline possible in the shortest amount of time. To be able to do

this, they have to constantly monitor and improve their method of pipeline installation

and production. With this in mind Allseas has been the originator of this research.

Before the research is further explained an introduction to Allseas and the installation

and production of pipelines is given.

1.1.1 Allseas

The Swiss-based Allseas Group S.A. is a global leader in offshore pipeline installation

and subsea construction. The company employs over 2,000 people worldwide and oper-

1

1. INTRODUCTION

ates a versatile fleet of specialized pipelay and support vessels, designed and developed

in-house [7].

The basis of this fleet, are the pipelay vessels (PLVs):

• Solitaire (300 m)

• Audacia (225 m)

• Lorelay (182.5 m)

• Tog Mor (111 m)

All vessels are capable of handling pipelines with outside diameters (OD) ranging

from 2 inch to 60 inch, except for PLV Lorelay, which is limited to a maximum OD of

28 inch. PLV Solitaire has achieved pipelay speeds in excess of 9 km/day [7].

Currently Allseas is building her fifth PLV, the Pieter Schelte. She will be commis-

sioned in 2014. The Pieter Schelte will then be the biggest PLV in the world with an

overall length of 382 meter. She will be capable of laying pipelines up to a maximum

OD of 68 inch.

The philosophy within Allseas has always been to develop and design its own equip-

ment, ranging from the Phoenix welding system up to the biggest pipelay vessel thus

far, the Pieter Schelte. From this philosophy the department of Innovations has tried

and tested numerous different methods of pipeline production and continues to perfect

and adapt its equipment. The main reason to apply this philosophy is to stay ahead of

the competition and to be independent from (sub) contractors. Allseas uses a specific

method of pipeline installation which is explained in the next section.

1.1.2 Pipeline installation

There are a number of different methods for the offshore installation of pipelines. The

choice for each one of these methods relies on a number of factors. The most important

being water depth and the OD of the pipe. For Allseas two methods are suited. The

first method is the so called S-lay method. The second is the so called J-lay method

[8]. The letters S and J, describe the shape of the pipeline from the PLV to the ocean

floor.

2


With the J-lay method the pipeline is produced in a vertical tower. At the deck level

al the steps to produce the pipeline are performed in the same station. S-lay describes

the method of pipeline installation where the pipeline is produced horizontally.

The main advantage of S-lay is the fact that it is possible to simultaneously conduct

several steps needed for pipeline production. These are done in multiple stations along

the length of the ship. There are different stations for welding, non-destructive testing

(NDT) and field joint coating (FJC).

The pipeline follows the shape of the letter S, from the vessel to the bottom of the

sea as seen in figure 1.1. To support the pipeline while leaving the vessel a stinger is

attached. The stinger is a support structure that limits the bend radius of the pipeline

and prevents buckling of the pipeline.

Figure 1.1: S-lay method

Several tensioners fitted with tracks hold the pipeline in the vessel. The tensioners

are controlled to move the pipeline in and out of the vessel. This is done automatically

to compensate for vessel motions due to waves. The deeper the pipeline needs to be

installed the higher tension is needed to hold the pipeline with the tensioners.

Allseas has designed and developed systems for J-lay and S-lay installation. The

choice was made for the S-lay method because this method provides fast installation

for all pipeline ODs over a large range of water depths in comparison with the J-lay

method [8]. The choice for the S-lay method resulted in a specific layout of the pipeline

production, which is described in the next section.

3

1. INTRODUCTION

1.1.3 Pipeline production

The production process of a pipeline can be compared to a standard production process

in a factory. A piece of pipe, called a joint, enters the factory. During the production

process joints are connected to form a continuous pipeline. The factory is the firing

line (FL). Production rates can be increased with the addition of a double joint factory

(DJF) to the FL. In the DJF two single joints are connected to form a double joint

before entering the FL.

Firing line

In each of the four PLV’s of Allseas the joints are transformed in a continuous pipeline

in the firing line. The FL is situated along the length of the vessel. It is divided in a

number of work stations. There are a number of consecutive stations where the welding

of the joints takes place. In figure 1.2 the firing line of PLV Solitaire is presented.

Figure 1.2: Firing line on board PLV Solitaire

When two joints are welded together both cut-back sections together are called a

field joint (FJ). A cut-back is the bare section on both ends of the joint. In the next

station the weld is checked with ultrasonic sound, this station is called the NDT station.

4


Finally there are a number of stations that together perform the task of coating the

FJ.

During each production cycle each station performs its individual task. When the

task is completed the operator gives a signal. Once all stations have signalled they are

ready, the pipeline can move to the next station. The distance that the pipeline moves

between stations is called a pull. The vessel moves forward in the lay direction and the

tensioner pays out the length of one pull. Each FJ then arrives at the next station,

while the last FJ moves to the stinger.

In figure 1.3 a schematic overview of the FL of the Solitaire is presented. On the

bow of the vessel the FL starts with the welding stations. At the stern of the vessel,

the stinger is situated.

Figure 1.3: Schematic overview of the firing line of the Solitaire

Double joint factory

In order to increase lay rates the Solitaire is equipped with a Double Joint Factory

(DJF). In the DJF single joints are welded together to form a double joint. The firing

line of the Solitaire is therefore twice as long as that of the other vessels. The newly

build Pieter Schelte will also be equipped with a double joint factory. In the DJF joints

are welded and the weld is inspected with NDT. Coating of the welded double joint

does not take place in the DJF. Coating takes place in the FL where more FJC stations

are available.

5

1. INTRODUCTION

1.2 Problem definition

During the pipeline production process it is important to minimize the time that each

joint has to be in a single station (cycle time), whether it is one of the welding stations,

NDT or FJC stations. Furthermore it is important to synchronise the cycle times

of the stations with each other. This results in an optimal usage of the production

potential. The reduction in cycle times lead to lower overall production process times

and minimizes project costs.

To achieve this, a lot of attention over the past years was given to the welding and

NDT process. Welding over the years has become more reliable with the introduction

of the automated Phoenix welding system and cycle times have thus been reduced and

became more constant. With the automation of non-destructive testing and welding

the chances on defects and repairs have also been greatly reduced [9].

There is a tendency now to pay more attention to FJC. During recent projects it

has been observed that cycle times of FJC stations were not coherent with welding

and NDT. One of the approaches from Allseas was to build the combined heat and

coat machine. The machine was capable of performing two steps in one. The machine

however was bulky and not optimised, which resulted in a bad coating quality. Another

step was the introduction of a wheelabrator (mechanical grit blast machine) in the FL.

The principle was promising but the fixed nature of the machine was not ideal for use

in the FL.

Although an effort was made in the past to improve the coating process the results

were disappointing. The need for reducing overall process times while maintaining

coating quality however remains. Therefore Allseas initiated this research, exploring

possible changes to the coating process.

1.3 Relevance of the research

The coating process within Allseas has a number of variables depending on the project.

For each project the FJ has to be coated to protect it against corrosion. This first

layer of coating is called the anti-corrosion coating and is always applied to the FJ.

Optionally a second coating can be applied to protect the pipeline against mechanical

damage or to insulate the pipeline.

6

1.3 Relevance of the research

For each project the client in cooperation with Allseas decides on the type of anti-

corrosion coating that will be applied. The choice for the type of coating also decides

the type of surface preparation that must be done. Three types of anti-corrosion coat-

ing can be distinguished: liquid epoxy (LE), fusion-bonded epoxy (FBE) and a heat

shrink sleeve (HSS). Two types of surface preparation can be distinguished: power wire

brushing (PWB) and air pressured grit blasting. When FBE is chosen, this automat-

ically means that grit blasting is used for surface preparation. For LE and HSS both

types of surface preparation can be chosen.

A preliminary research in to the choice for each of these types was done to establish

the relevance of the research. With the results from this preliminary research a scope

can be defined for the actual research.

1.3.1 Field joint coating project data

Analysis of available project data gives an indication of the relevance of the research

of FJC application. The analysis is based on track records Allseas has of past projects

and the known characteristics of planned projects. Due to missing data in this track

record the overview is based on data from 2008 up until 2014. The overview is based

on the number of FJs made in each of the pipeline installation projects for al PLVs

combined.

Figure 1.4: Percentage of field joints per surface preparation method

7

1. INTRODUCTION

In figure 1.4 it can be seen that PWB was used for a great part in past. This has

changed however. The use of grit blasting has risen. This can be explained by the rise

in use of FBE as a FJC, which requires grit blasting. This can be seen in figure 1.5.

In that figure it can also be seen that the use of HSS has diminished. LE is still used,

but for limited amount of projects.

Figure 1.5: Percentage of field joints per coating type

From interviews with coating engineers from Allseas it became clear that in the

future the use of HSS and LE will further diminish. The demand from clients of

Allseas will mainly be FBE. As a result grit blasting will be the predominant choice

for surface preparation.

1.3.2 Scope of research

Based on section 1.3.1 it can be concluded that FBE will be the most used field joint

coating for the coming years within Allseas. The scope of this research will therefore

lie on the application process of FBE. Another reason for this scope is the practical

implementation. If changes to the process can be found which reduce the overall process

times it will be possible for Allseas to benefit from these changes on a short term.

Completely new forms of coating could possibly require more time to fully research and

implement and are therefore out of the scope of this research.

8

1.4 Goal of research

Because the FBE coating application process only takes place in the FL, the DJF

on Solitaire lies outside of the scope. The scope of the research will be on the FL itself.

The application process of secondary coatings lies outside of the scope because the

choice for secondary coatings is not as regularly as the application of anti-corrosion

coating.

1.4 Goal of research

With the scope of the research defined in section 1.3.2 and the problem definition from

section 1.2 the goal of the research can be set. This is done by first formulating the

main research question, after which the approach of the research can be defined.

1.4.1 Research question

The main research question is formulated as follows: ’What are the possibilities to

change the current process of field joint coating application, in order to achieve faster

cycle times while maintaining the current coating quality, while taking into account

requirements for changes to the process?’

To answer the main research question there are a number of sub-questions to be

answered. These questions are:

I What is the current process of FJC application?

II What equipment is used in the current process?

III What are the cycle times within the whole process of pipeline production?

IV What defines the level of quality of field joint coating?

V What changes could be made to the current process?

VI What are the requirements for changes to the process?

VII What alternatives are available for the process and the equipment?

VIII Which of these alternatives can lead to faster cycle times?

IX Can these alternatives maintain the current quality level of field joint coating?

X How can alternatives be implemented in the current process of pipeline installation?

9

1. INTRODUCTION

1.4.2 Approach

To answer each of the sub questions a certain approach is necessary. The approach for

each of the question will be as follows:

I Analyse the current FBE application process through in-house literature and inter-

views with Allseas employees to find possibilities for changes.

II Analyse the current FBE application equipment through in-house literature, inter-

views with Allseas employees and a visual inspection of the equipment at the

storage facility to find possibilities for changes.

III Analyse the project data that is available within the Pipeline Production depart-

ment to get cycle times for different projects and to find which possibilities for

change would have to most effect on overall cycle times.

IV Study publications and in-house literature on the topic of coating to find the pa-

rameters which define the level of quality of coating and the methods to asses

this level.

V List the possibilities for changes based on the findings of I, II and III.

VI Study publications and in-house literature and interview employees to find the

requirements for changes to the process.

VII Find alternatives for the possibilities for changes as found in V through a literature

study, interviews with Allseas employees and interviews with suppliers of coating

equipment.

VIII Measure the cycle times of alternatives found in VII trough practical tests and

project these times on the real-time process.

IX Measure the quality of the coating that has been made through practical tests

based on the findings of IV.

X Give an advise on the implementation of the alternatives based on the findings of

VI, VIII and IX.

10

1.5 Structure of the report

1.5 Structure of the report

The structure for the report will be as follows; In chapter 2 an analysis of the pipeline

production process is given. In chapter 3 an analysis of the equipment used within the

FJC process is given. In chapter 4 alternative application methods for the FJC process

are researched. Based on found requirements the most promising ones are chosen. In

chapter 5 the chosen alternatives are tested. Finally in chapter 6 the results of the tests

are discussed and conclusions are drawn.

11

1. INTRODUCTION

12

2

Analysis - process

In this chapter an analysis will be made of the current process of pipeline production

and the application of FBE as a field joint coating in particular. The whole process is

analysed to give an indication of the role of the FJC process in the whole pipeline pro-

duction process. The analysis should point out which possibilities there are to change

the process of pipeline production. The analysis starts with stating the requirements

for the pipeline production process in section 2.1. The process is described in sec-

tion 2.2. In section 2.3 an indication of the cycle times of the stations is given. Finally

in section 2.4 conclusions are drawn with respect to possibilities for changes of the

process.

2.1 Requirements for the pipeline production process

To get an insight in the pipeline production (PP) process the requirements for the

process are researched in this section. Requirements for the PP process in a certain

project can be given from one actor to another actor. They can also be discussed

and agreed upon by multiple actors. Four different actors can be distinguished in this

process:

1. Allseas

2. Clients

3. Suppliers

4. Independent parties

13

2. ANALYSIS - PROCESS

Clients are oil and gas companies who contract Allseas to install pipelines. Suppliers

are companies who supply Allseas with equipment and / or consumables. Equipment

can range from components to whole machines. Consumables can be grit for the grit

blaster or FBE powder used in the coating machine. Independent parties can be gov-

ernments or organisations like ISO, DNV or Lloyds. They standardise and formalise

the requirements for pipeline construction and installation.

Requirements for a project are driven by the client and determined in detail in

corporation with Allseas. These requirements can be categorized in three themes;

Time For Allseas to be competitive and be successful as a commercial company the

main goal for the process of PP is to make as much pulls as possible in a given amount

of time. To achieve this goal the cycle time of each of the individual work stations needs

to be as low as possible. Next to that the cycle times per station need to be as close

together as possible to use the production capacity to a maximum. The station that

uses to most time to perform its individual task is called critical. The time needed for

this station is the governing time for the total process time and the amount of pipeline

that can be installed per day.

Quality The process needs to result in a pipeline that adheres to the agreed level of

quality. This means that the process is designed in a certain way. Surface preparation

for instance needs to take place before coating can be applied. It may be possible to

make changes to the process while still adhering to the level of quality.

Safety and Health Within Allseas there is a Quality, Health, Safety and Environ-

ment (QHSE) department. This QHSE department has the specific task of monitoring

all the processes that take place within Allseas. One of their main tasks is the safety

and wellbeing of employees. The PP process therefore needs to be designed in such a

way that the safety and wellbeing of employees is guaranteed. Where possible, safety

measures should be incorporated in the process.

2.2 Process description

In this section the complete process of pipeline production is described. In the PP

process four main steps can be distinguished: pre-production, welding, NDT, and FJC.

14


A schematic overview of these four steps can be seen in figure 2.1. The first step

pre-production takes place before the FL. The other three steps combined form the FL.

Pipeline production process

Firing Line

Non distructive testing

WeldingField Joint

CoatingPre-production

Figure 2.1: Scematic overview of the process

Each of the steps is performed in a separate work station. Table 2.1 gives an

overview of the number of stations on each of the PLV’s of Allseas. The number of

stations used depends on the project. For smaller pipeline OD’s with smaller wall

thicknesses (WT) less welding stations could be used than there are available.

Vessel Welding stations NDT stations FJC stations

Pieter Schelte 6 1 6

Solitaire 5 1 4

Audacia 7 1 3

Lorelay 6 1 3

Tog Mor 3 1 1

Table 2.1: Firing line stations overview

In the next sections the processes during pre-production and in stations in the FL

are further explained.

2.2.1 Pre-production

The pipeline is produced in the FL, before the FL there is a pre-production process.

In this pre-production process the joints that form the pipeline are prepared for the

process of the firing line.

The steps in the pre-production process are bevelling of the joint, cleaning of the

inside of the joint and finally heating of the ends of the joint. These steps can be seen

15


in the schematic overview in figure 2.2.

Pre-production

Pro

cess

st

ep

CleaningBeveling Heating

Figure 2.2: Process of pre-production

Joints come in a standard length of 40 feet (12.2 meter). Joints come in different

sizes with respect to OD and WT [8]. The choice for OD and WT are based on the

function of the pipeline. These functions can be roughly divided into three categories

as shown in table 2.2. These are not set values. Other combinations are possible as

well.

Type OD [inch] Length [km]

Infield 6 - 12 1 - 30

Trunk lines 10 - 24 10 - 70

Export lines 24 - 42 100 - 1000

Table 2.2: Joint types

Joints are made of steel and WT ranges from 12 to 41 mm. Joints are supplied with

a factory applied coating which is called the parent coating. The ends of the joints are

left bare for welding and NDT. This bare end is called a cut-back. The length of the

cut-back ranges from 100 to 250 mm.

Joints are supplied by different companies depending on the job location. The way

joints are transported, stored and handled form supplier to the vessel has led to many

different surface conditions of the cut-back. These conditions can range from mild rust

to severe pitting. Severe corrosion on the cut-back has a negative effect on the time

needed to prepare it for the FL.

The first step is making a bevel. Depending on the type of weld two different bevels

can be made. If the joint is welded from the inside and the outside a so called K-bevel

is made. Welding from the inside can only be done in the DJF. If the joint is only

16


welded from the outside a so called J-bevel is made. In the FL the FJ is only welded

from the outside. In figure 2.3 an example of both bevels can be seen.

Figure 2.3: Example of a J-bevel and a K-bevel

To make the bevel a machine is inserted in the pipe. It machines the edge of the

cutback in the required bevel. The machine also brushes the cutback to prepare it for

welding.

After bevelling the joint is cleaned from the inside. This is done to prevent foreign

objects being left in the pipeline during or after production.

Once the joint is cleaned the cut-back is heated with a heating coil. This is done

to prepare for the welding process in the FL. After heating the joint can enter the FL.

2.2.2 Welding

Welding

Sta

tio

n

Pro

cess

st

ep

Intermediate stations (2-4/

5/6)

Bead stall (Line-up

station 1)

Final station (5/6/7)

Filler (hot) passRoot pass Cap weld

Figure 2.4: Process of welding

Before welding starts, the new joint is lined up against the existing pipeline. This

is done with a line-up car. The line-up car is controlled by an operator. The operator

17


can manoeuvre the joint in all directions. When the joint is lined-up correctly the first

weld is made. The first weld is called the root pass. The root pass is a full pass around

the circumference of the pipe. This weld must be strong enough to withstand the forces

of a pull. After the root pas, the next stations make the filler (hot) pass. In the final

welding station the last weld is laid which is called the cap. The steps of the welding

process can be seen in figure 2.4. The build-up of the welds can be seen in figure 2.5.

Figure 2.5: Build-up of welds in the pipeline wall

The number of welding stations used is based on the amount of welding that needs

to be done. This in turn depends on the WT and OD of the pipeline. The first (root

pass) and the final (cap) welding station are a given. The number of stations in between

depends on the amount of welding that has to be done. It is distributed over these

stations so none of them can be critical. Cycle times of the first or last welding station

are leading. In each station welding is done until the pull can be made. When a pull

can be made the particular station stops welding and marks the end point. The next

weld station then resumes welding from the spot the previous station has marked. Once

the final weld is made, the whole weld has to be checked for defects in the next station.

2.2.3 Non-destructive testing

After welding the quality of the weld must be checked. This is done in the NDT station.

In the past this was done with X-ray, when photos were made of the weld. These photos

were then inspected. The downside of these photos was their size: they were the same

scale as the weld itself.

18


X-ray testing has now been replaced with automatic ultrasonic testing (AUT). With

AUT the images appear on computer screens and can be enhanced for a more detailed

view. AUT works with sound waves that penetrate the metal trough water as a coupling

medium. This water also cools the FJ, which is still hot from the welding process. After

leaving the NDT station the FJ temperature is around 120 degrees Celsius.

The AUT device moves on a rail along the circumference of the pipe. The results

can be seen instantly on computer screens. If unacceptable weld defects are detected

they must be repaired. A partial section or the whole joint can be cut out for repairs.

If a repair has to be made, overall production time is greatly affected. The pipeline

has to be pulled in and the repair has to be made. This results in the loss of valuable

production time.

If the weld passes NDT it can progress to the next station where the FJC application

process starts.

2.2.4 Field joint coating - FBE

The application of FBE as a field joint coating is a three step process. In the first step

the surface area of the FJ is prepared. In the second step the FJ is heated. The final

step is the application of the FBE coating. These steps can be seen in figure 2.6. In

figure 2.7 a typical layout of a FJ can be seen.

Multiple stations are available for coating application. The first station is for surface

preparation. The second station is for the application of the anti-corrosion coating.

Other stations can be used for secondary coatings. As mentioned in chapter 1 these

lay outside of the scope of this research.

Grit blasting is the process where a blast medium is accelerated by compressed air

against the FJ. This takes place in the first FJC station. Once the FJ has been blasted

a protective sleeve is applied around the FJ. This is done to protect the cleaned surface

while it goes through the tensioner to the next station.

In the next FJC station the FBE coating is applied. This is a two-step process that

takes place in the same station.

For the application of FBE coating the FJ needs to be heated to a certain temper-

ature. This is done with an induction coil. Once the required temperature is reached

the coil is taken off. The coating frame is then put on the pipe. This switching of

equipment takes time. Once the coating is applied the coating frame can be taken off.

19


Field Joint Coating (FBE)

Sta

tio

nP

roce

ss s

tep Station

Coating application 1

Surface preparation

FBE coating application

Induction heating

Grit blasting

Figure 2.6: Schematic process overview of Field Joint Coating

Figure 2.7: Typical field joint

If necessary the coating can be cured by pouring water over the FJ. This is done by

placing a clamp with a water hose on top of the pipe.

2.3 Cycle time analysis

When a new tender for a project is prepared within Allseas, employees from the Pipeline

Production Departement (PPD) make an estimate of the total process time. This

estimate is based on the cycle times of each of the process steps as described in this

20

2.3 Cycle time analysis

chapter. From interviews with employees from PPD it became clear that the estimate

is not really based on databases with project data but more on experience. This meant

it was difficult to obtain data regarding cycle times.

Based on the limited available date from a number of projects the cycle times per

process step are summarised in table 2.3. Projects are named letters A to G. From this

data it can be seen that the FJC process step can become critical.

( critical ) OD Welding NDT FJC

Project [inch] [sec] [sec] [sec]

A 24 501 180 505

B 18 215 150 156

C 18 145 150 156

D 18 142 135 136

E 18 178 150 178

F 13 233 150 175

G 20 188 150 178

Table 2.3: Cycle times of the three main steps

From the projects in table 2.3 where FJC station were critical there was more data

available regarding cycle times of the individual stations. For two other projects H and

I also data was available with respect to cycle times of the FJC stations. These cycle

times are summarised in table 2.4.

( critical ) OD Surface prep Coating Heat Coat

Project [inch] [sec] [sec] [sec] [sec]

A 24 180 230 160 70

C 18 96 95 55 40

E 18 143 178 104 74

H 36 200 285 180 105

I 18 151 134 67 67

Table 2.4: Cycle times per station

From the cycle times from tabel 2.4 it can be seen that both the surface preparation

station and the coating application station can become critical.

21


From this limited amount of data it can be concluded that changes to the FJC

process and its stations could have an effect on overall process times.

2.4 Conclusions

From the analysis of the current method of pipeline production it can be concluded

that there are three possibilities for changes to the process that could have an effect on

the overall process time.




Although limited, an analysis of cycle times showed that this would indeed have an

effect.

The three possibilities for change are further researched in chapter 4. Before this

can be done an analysis of the current methods within each of the process steps of FJC

must be made, which is done in the next chapter.

22

3

Analysis - equipment

In this chapter an analysis is made of the current equipment that is used for the

application of FBE as a FJC. In section 3.1 requirements are given for the application

equipment. Surface preparation is analysed in section 3.2. Coating application is

analysed in section 3.3. Finally in section 3.4 conclusions on possibilities for changes

are drawn based on the analysis.

3.1 Requirements for equipment

In this section the requirements for existing equipment are described. These require-

ments can also be used when developing new equipment.

Quality As with the process, the use of specific equipment should result in a agreed

level of coating quality. This level of quality is agreed upon by clients of Allseas and

Allseas themselves. It is described in client specifications. In these client specifications

it is stated which equipment should be used and which procedures should be followed

to assure an acceptable quality level of the coating.

Before the project is executed offshore, Allseas performs a Procedure Qualification

Trial (PQT). During a PQT Allseas shows the client in which manner the coating is

applied. After the coating is applied it must be shown that the agreed level of coatin

quality is achieved. For this purpose the applied coating is subjected to quality tests

as described in specific norms and standards. For FBE coating the quality tests as

described in ISO norms 21809 and 8501-1 are performed.

23

3. ANALYSIS - EQUIPMENT

Practical The available space on board the vessels is limited. This means equipment

must be kept within certain dimensions to fit inside the FL or storage areas. The same

holds for consumables used by the equipment.

The possibility to implement a new alternative based on current machinery and

infrastructure is an advantage. Extensive changes to the vessels layout to fit equipment

are not desirable, unless this could be justified with the performance of the equipment.

Financial Operational costs for equipment should be minimised. These costs come

from:

• Building the equipment: cost of development and costs of components

• The transport and use of consumables

• Operators of the equipment

• Energy consumption of the equipment

With new equipment, investments must be made. If operators have to operate new

equipment, investment in training must be done as well.

Safety and Health Operator safety is an important issue when using equipment.

The QHSE department has the specific task to ensure equipment can be used in a safe

manner. When designing or buying new equipment the safety aspect must be kept in

mind.

3.2 Surface preparation

Prior to the application of the anti-corrosion coating, the surface of the FJ needs to be

cleaned. In this preparation the surface is cleaned and corrosion is removed. Depending

on the type of coating there are different methods with different results. Anchor profile

and surface cleanliness are leading in the choice for which method. Allseas uses two

methods, power wire brushing or grit blasting.

Currently for the application of FBE the surface is always prepared with grit blast-

ing. Grit blasting is the process in which grit is propelled at a high velocity by way of

pressurized air against the substrate. Due to the shape and speed of the grit this has

24


an abrasive effect. Depending on the conditions of the FJ the grit blaster is capable of

cleaning up to 20 m2/hr [10].

The goal of grit blasting is to get a surface that is:

• clean: cleanliness of SA 2.5

• rough: anchor profile created of 32-100 microns

These are two important requirements. The cleanliness is defined by the ISO norm

8501-1, where SA 2.5 stands for: Mill scale, rust paint and foreign matter are removed

completely. Any remaining traces are visible only as slight stains or discoloration in

the form of spots or stripes. The anchor profile is a measurement of the roughness of

the surface. This is measured from the lowest point to the highest point of the surface.

In figure 3.1 two examples of surface roughness can be seen.

Figure 3.1: Anchor profiles on substrate; left is shallow, right is deep[1]

Clients of Allseas for the most part specifically request for the grit blaster to be

used as a method of surface preparation if FBE is used as a coating.

3.2.1 Blast media

The blast media used for grit blasting is a mix between shot and grit. Shot particles

have a rounder shape and act as a cleaner. Grit particles have sharper edges that create

the required anchor profile. The correct mix between the two components is important.

Blast media has a limited life time as it deteriorates due to impact forces. This means

that during a project Allseas has to carry sufficient blast media on board the vessel.

25


Since the blast media that Allseas uses is made of steel particles it has to be stored

under controlled circumstance to prevent corrosion.

A sample of the blast media Allseas uses can be seen in figure 3.2.

Figure 3.2: Sample of blast media: steel shot and grit mix

3.2.2 Blast frame

Allseas developed an automatic frame in which two grit blasting heads are mounted.

The blast heads are positions opposite of each other. Each cleans one half of the FJ.

The heads can rotate and translate around the FJ [11]. This is done with electric

motors which are controlled by a control panel where the speed in both directions can

be pre-set. The frame is presented in figure 3.3.

The blast head is a closed loop system: a combination a nozzle and a suction part.

The nozzle ejects the grit; the suction part surrounding the nozzle removes the grit

mixed with dust particles. The used grit is sucked away to be filter and re-used.

During a noise survey on board PLV Lorelay measurements were taken on multiple

locations in the FL during production. These measurements were taken by a third

party. Results from these measurement show that for the grit blaster noise levels of

97 dB were reached [12]. To protect operators double hearing protection was advised.

The QHSE department within Allseas also expressed their wishes for a reduction of

noise levels from the grit blast equipment.

26


Figure 3.3: Grit blast frame in operation on the pipe

In recent projects there were signals that the grit blast process would be critical.

To speed up the cycle time of grit blasting two additional heads were fitted to the blast

frame. This led to lower cycle times but created another problem which is described

in section 3.2.3. Exact cycle times could not be found, but interviews with Allseas

employees confirmed the reduction of cycle times when using four blast heads instead

of two.

3.2.3 Grit handling units

The grit is processed in the grit handling units. These units are made by LTC. Therefore

they are named LTCs. In figure 3.4 an LTC can be seen.

In the LTC dust and rust particles are separated from returning stream of grit. The

cleaned grit is then mixed with the compressed air and fed back to the blast heads in

blast frames.

With the addition of more blast heads, more LTCs were needed. The capacity of

the existing LTCs was not sufficient. This created a problem since the LTCs are placed

in the so called Green Mile where space is already limited.

27


Figure 3.4: Grit handling unit - LTC

The Green Mile is a hallway situated alongside the FL. It is used by personnel to

reach the different stations. It is also used to store other equipment and consumables.

During pipeline production this normally is a crowded area. In figure 3.5 the green

mile of PLV Solitaire can be seen.

When new equipment is introduced within the PP process the availability of space

is an important matter to take into account.

28

3.3 Coating application

Figure 3.5: Green mile of PLV Solitaire


After the surface preparation mentioned in section 3.2 the anti-corrosion coating can

be applied in the next station. In the coating station, multiple machines are used in a

sequence.

3.3.1 Heating coil

Prior to the application of FBE and HSS it is necessary to heat up the FJ. FBE requires

a temperature in the order of 230 degrees Celsius, while the application of HSS needs

a lower temperature of 180 degrees Celsius.

To achieve this temperature an induction heating coil [2] is used. This coil is wound

around the FJ and a large AC current goes through. The AC current has a frequency

of 2000 to 3000 Hz. The power is in the order of 100 to 500 kW.

The generated heat comes from the eddy currents which flow through the pipe as

a reaction on the electromagnetic field the coil creates. In figure 3.6 a heating coil can

29


be seen. The thick red leads form the actual coil. The frame encloses the leads around

the FJ.

Figure 3.6: Heating coil

Induction heating is the most efficient and clean way of heating the pipe[13]. The

shape of the coil determines the heating profile generated in the pipe. Due to the

parent coating (factory applied coating) on the joint it is necessary to maintain the

heated zone within the FJ. If the heated zone is greater than the width of the FJ the

parent coating can be damaged by the generated heat. This will result in bad adhesion

of parent coating to the pipe or parent coating to the applied coating. A schematic

overview of the heat profile along the FJ can be seen in figure 3.7.

3.3.2 Fusion-bonded epoxy

Fusion-bonded epoxy is a one-part thermosetting epoxy resin powder that uses heat

to melt, crosslink and adhere to the metal substrate [14]. FBE being one part means

no solvents are involved. During the manufacturing of FBE the resin and the curing

agent are pre-mixed. The reaction between the two is incomplete and continues when

the resin is reheated during the FJC application process.

FBE has a number of properties which are suited for pipeline coating:

• Physical and chemical stability

• Resistance to soil stress and loads

30


Figure 3.7: Heat profile along the field joint[2]

• Adhesion and resistance to impact

• Resistance to cathodic disbondment

When FBE is used as a coating the required thickness can vary between 300 and 500

microns. The choice for the applied thickness depends on the function of the coating.

FBE can be the only coating which will be applied to the FJ. The thickness of choice

will then be in the order of 500 microns. If FBE is applied as an anti-corrosion coating

where more layers of other types of coating will be applied, the thickness will be in the

order of 300 microns.

3.3.3 Coating machine

The coating machine is used to apply coating. The complete coating machine is made

up of two parts. The first part is the automatic spraying frame. The second part is the

fluidised bed, which supplies the frame with FBE powder.

Application frame

The spraying of FBE powder is done by standard spray nozzles. These nozzles are

fitted in a ring that spans over the circumference of the FJ[15]. The ring moves along

31


the pipe and rotates with increments. The movement is controlled by a program, which

is set to apply the required coating thickness.

In figure 3.8 the frame can be seen.

Figure 3.8: FBE coating frame

Due to the lay-out of the nozzles in the ring there is an overlap in powder streams.

This ensures a full coverage of the FJ, but more FBE powder is sprayed than necessary.

The ring is equipped with an extraction system for the excess powder. The inside of

the ring can be seen in figure 3.9. In the centre the nozzles are placed. On both sides

the extraction hoses are placed. The problem of excess spraying will not be further

investigated in this research. From interviews with Allseas employees it became clear

that this problem does not have a negative effect on cycle times.

Figure 3.9: Inside of the coating ring of the application frame

32

3.4 Conclusions

Fluidised bed

The fluidised bed gives the FBE powder the characteristics of a fluid so it can be applied

to the FJ. A fluidized bed is a drum where pressurised air (2.5 bars) is blown in from

the bottom through a mesh. The mix of air and powder has fluid properties. Via a

venturi pump the powder is transported through hoses to the spray nozzles. When

FBE application starts the operator opens the electromagnetic controlled valves on top

of the barrel so the powder can flow to the nozzle.

Figure 3.10 shows the fluidised bed together with the control panel. The barrel can

be seen behind the control panel in this figure.

Figure 3.10: Fluidised bed together with control panel

3.4 Conclusions

From the analysis of the equipment used for FJC application of FBE a number of

conclusions can be drawn.

For surface preparation grit blasting is an effective method for reaching the de-

sired anchor profile and cleanliness. However there are a number of possibilities for

improvements:

33


• Noise level of the grit blaster

• Usage of consumables (blast media)

• The required space for supporting equipment (LTCs)

Regarding the heating of the FJ, the principle of induction heating is the most

suitable. A possibility for change could lie in the shape of the coil. If the shape of the

current induction coil could be changed it could be possible to combine the coil with

other process steps.

These possibilities for change will be further explored in the next chapter. There

they will be combined with the conclusions regarding the process from chapter 2 to

find possible alternative application methods.

34

4

Alternative application methods

In this chapter possible alternative application methods are explored. The alternatives

are based on the possibilities for improvement as identified in chapter 2 and chapter 3.

Alternatives for the process of FJC are explored in section 4.1. Alternatives for

surface preparation are given in section 4.2. In section 4.3 alternatives for coating

application are given. In section 4.4 alternatives application methods are formed based

on the findings of section 4.1 , section 4.2 and section 4.3. Finally in section 4.5

conclusions are drawn based on the formed alternative application methods.

4.1 Process alternatives

From the analysis of chapter 2 two possibilities for changes of the process were found.

The order of steps within the process or the combination of steps within the process

could be changed. In this section both options are further explored.

4.1.1 The order of steps within the process

Following the dismantling of the mechanical blast installation there were ideas within

Allseas to re-use the equipment in a different way. The main idea was to salvage the

parts of the old machine and come up with a machine that could blast the cutbacks of

the joints prior to the entry in the FL. In the FL the joint would be blasted again with

the conventional air pressured grit blaster. This would effectively mean a two stage

blasting process. A schematic overview of the process can be seen in figure 4.1.

35

4. ALTERNATIVE APPLICATION METHODS

Pipeline production – two stage blasting

Firing Line

Non distructive testing

WeldingField Joint

CoatingPre-production

Surface preparation – anchor profile

Surface preparation -

clean

Figure 4.1: Pre-blast process

In this process the pre-blast would create an anchor profile. During the processes

of the FL the FJ gets contaminated with weld spatter and NDT water. So therefore

just before heating and coating another blast sequence should be implemented to clean

the FJ again. As the anchor profile was already created this second blast step could

be done quicker. The parts of the old mechanical grit blast machine proved not to be

useful again.

Tests were done with the pre-blasting concept. In these tests the conventional air

pressured grit blaster was used for both stages. In these tests it was concluded that a

time reduction of up to 30 % was achievable[10]. After these tests there has not been

a follow up with the actual application of coating or the research of the possibility of

implementing this.

Therefore the option of pre-blasting should be further explored. It could be possible

to use different methods for creating the anchor profile and cleaning of the field joint.

An important factor that must be incorporated within the pre-blast process is the weld

surface. When the joint is pre-blasted there is an anchor profile on the cut-back. Once

two joints are welded there is no anchor profile on the weld surface. During cleaning in

the FL it should therefore be possible to make an anchor profile.

Possible methods that could be used in the pre-blast process are further explored

in section 4.2.

36

4.1 Process alternatives

4.1.2 Combination of steps within the process

In the application process of FBE there are three steps that can be distinguished,

surface preparation, heat and coating. Due to the layout of each of the FL it is only

possible to combine the heat and coat steps. In the FL the surface preparation station

lies before the tensioner while the heat and coat station lies after the tensioner. Coating

before the tensioner is impossible due to the fact that the tensioner would destroy the

freshly applied coating. Heating before the tensioner would melt the friction pads and

possibly more components of the tensioner itself.

Figure 4.2: FBE application dishes

The possible combination of heat and coat has been tried by Allseas in 2004. A

combined heat and coat machine was designed and built. A schematic view of the

process with the combined heat and coat machine can be seen in figure 4.3.

At that time FBE was applied by oval dishes instead of the now used nozzles. These

oval dishes had an advantage of being low profile and thus could be positioned between

the pipe and the heating coil as can be seen in figure 4.2. The dishes however had a

negative effect on coating quality. They were incapable of applying a constant quality

of FBE coating.

Next to that the dishes deteriorated during operation because of friction between

the FBE powder and the dishes. This resulted in unwanted downtime due to repair and

maintenance. Another downside of this combination was the overspray of FBE which

37


Field Joint Coating

Sta

tio

n

Pro

cess

st

ep


Surface preparation


Combined Heat & coat

machine

Figure 4.3: Combined steps process for heat and coat machine

nested itself on the heating coil and its parts. Mainly affecting the copper contact blocks

that close the current loop of the induction coil as shown in figure 4.4. The build-up

of FBE rendered them useless after a number of cycles, leading to more downtime due

to replacement.

Figure 4.4: Contact blocks of heat and coat machine

Two distinct upsides to this combination however were the elimination of the

change-over time from the heating coil to the coating frame. Next to that the heating

38

4.2 Surface preparation alternatives

coil could be set to a lower temperature as it was not necessary to compensate for the

heat loss during change-over.

Recently Allseas has changed the application of coating from dishes to nozzles. From

interviews with Allseas personnel it became clear that dishes are no longer preferred

as the nozzles perform much better. This makes building a combined heat and coat

machine impossible. Nozzles need a certain distance from the object on which they

spray for a cone to form which applies an even layer of coating. This distance is not

present between the heating coil and the pipe as can be seen in figure 4.5.

Figure 4.5: Spacing between the heating coil and pipe

It can be concluded that with the adaptation of current equipment it is not possible

to build a combined heat and coat machine. For this purpose new methods of heating

and coating application should be further explored.


Based on the conclusions from section 4.1 in this section possible alternative methods

are further explored with respect to surface preparation.

4.2.1 Mechanical blasting

Mechanical grit blasting is a method of surface preparation in which the abrasive media

is propelled to the substrate. This is done by wheel that is driven by either an electric

39


or a hydraulic motor. The flow of blast media is regulated with an impeller in the

centre of the throwing wheel. The blast media is fed into the impeller through a chute.

A mechanical blaster can be seen in figure 4.6. The main advantage of mechanical

blasting is the simplicity of the machine with respect to a conventional air pressured

grit blaster.

Figure 4.6: Mechanical blasting machine [3]

Allseas has tried to incorporate such a system in 2005. This mechanical blaster was

fitted in the firing line as a permanent installation. It used six electric motors driving

six wheels that propelled the blast media at the FJ. This can be seen in figure 4.7

Although a good anchor profile was created, the system was not a success. Due to

difficulties with reclaiming of the blast media and the stationary character in de FL

in which the pipe could move to a certain degree with respect to ship motions, the

machine was discontinued.

When incorporated before the firing line it can be possible to make a stationary

mechanical blaster where the joint rotates. This approach will result in a simpler

mechanical blaster than the one used in the FL. This would make the mechanical

blaster an option for the pre-blast process.

40


Figure 4.7: Bauhaus mechanical blaster in FL

4.2.2 Laser blasting

Surface treatment with laser is a technique which is mostly applied in the aviation

industry. It is possible to clean metal surfaces with a powerful laser. The principle

behind this is shown in figure 4.8. The pulsating energy of the laser beam makes it

possible to treat the surface area. The amount of substrate material that is removed

depends on the intensity and the frequency of the pulsations of the beam.

This technique was introduced to Allseas in the past through a demonstration. In

the demonstration a limited number of steel plates cut from actual joints were treated

as shown in figure 4.9. The demonstration showed that it would be possible to clean

rusted steel surfaces although it was mentioned that it was not possible to create an

anchor profile.

These conclusions were later backed by a research done by Mitraco, another com-

pany involved in laser blasting. Mitraco did a study into the implementation of laser

blasting within Allseas. In the study it was stated that it was not possible to achieve a

certain anchor profile, but it would still be possible to get the desired coating quality[16].

Another company (SLCR) however claims that an anchor profile can be created.

Due to recent developments in laser technology, faster cleaning process time can also

41


Figure 4.8: Surface preparation with laser beam

Figure 4.9: Laser treatment of steel piece

be achieved. If that is the case, laser treatment would be an interesting alternative to

incorporate in the firing line as a cleaning method.

4.2.3 Dry Ice blasting

Dry ice blasting is a blasting technique that is based on air pressured blasting where

the steel grit is replaced as the blasting media with dry ice pellets. These pellets are

42


shown in figure 4.10. Dry ice is a solid form of carbon dioxide.

Figure 4.10: Pellets of dry ice used for blasting

The priniciple of dry ice blasting can be seen in figure 4.11. The cleaning effects of

dry ice blasting are realised by:

• Kinetic energy: impact of the dry ice on the substrate

• Explosive sublimation: the rapid expansion of the ice into CO2 gas accelerates

the contaminate removal process

• Thermo shock: the sudden cooling creates an intense thermal tension

• Embrittlement: the material hardens under cooling and can easily fracture and

be removed

This technique has already proven itself in other fields as an effective method of

substrate cleaning [4]. With dry ice it is possible to clean metal substrates. An advan-

tage of this method is the fact that there are no consumables left after impact. The

dry ice pellets sublimate into CO2 gas on impact.

Methods were developed by Cryotech in which an abrasive is added to the flow of

dry ice, making it possible to create an anchor profile. This would make dry ice blasting

suited for replacing the grit blaster. If blasting is only done with dry ice it could be

suitable for use as a cleaning method.

43


Figure 4.11: Principle of dry ice blasting [4]

4.2.4 Power wire brush

The standard PWB is only suited for the application of HSS and LE as it is not capable

of creating a proper anchor profile for the application of FBE. There are however new

types of brushes available. The wires in these brushes have a bend at the end. This

results in a picking action when the brush hits the substrate. In figure 4.12 such a

brush can be seen.

Figure 4.12: Power wire brush with hardend bent ends [5]

If the picking action of the brush results in the creation of an anchor profile, it

could be suitable for replacing the grit blaster. The pick brush could be placed in the

existing PWB frame, which can be seen in figure 4.13.

44

4.3 Coating application alternatives

Figure 4.13: Power wire brush frame

4.3 Coating application alternatives

Based on the conclusions from section 4.1 in this section possible alternative methods

are further explored with respect to coating application.

4.3.1 Heating coil

As mentioned in chapter 2 the heating coil is very effective. The principle of heating

by induction coil should not be changed. The geometry of the coil however could be

changed.

If a different geometry of the coil is used it might be possible to combine the function

of the heating coil with another function like coating application. Another shape of coil

that can be used is the pancake type coil. The pancake type is similar to the heating

coil in a household cooking plate. Multiple coils could then surround and scan the pipe.

Spray nozzles could be fitted between the pancake coils.

4.3.2 Shockwave induced spraying

Shockwave induced spraying (SISP) is a relatively new solid state spray process. It

was developed in 2001[6]. With SISP it is possible to deposit metals, alloys, cements

and polymers on many types of substrates. Fast opening and closing of a valve creates

45


shockwaves of gas. Powder is added to the flow of gas which exits the nozzle at a

very high velocity. The powder adheres to the substrate on impact. Because of these

characteristics it might be possible to grit blast and apply coating using the same

equipment. The SISP process does not require any pre-heating of the substrate.

After contact with a supplier it became clear that it has never been tested with

FBE. Due to developing heat in the gun it could get clogged up with reacting FBE. At

the moment no practical experience with the technique is available.

Figure 4.14: Schematic overview SISP process [6]

4.3.3 Low application temperature FBE

Beside conventional FBE powder, manufacturers offer a low application temperature

(LAT) FBE. This FBE can cure at a lower temperature of 180 degrees Celsius than

standard (230 degrees Celsius). This means less time is needed for the heating coil to

heat up the FJ and for the FBE to cure.

From interviews with coating engineers and Innovations personnel it became clear

that this option has not yet been fully explored. The price of LAT FBE could play an

important part in that decision. Compared to normal FBE it is twice as expensive.

The higher costs of LAT FBE could be justified if the use would lead to shorter

overall process times.

46

4.4 Choice of alternatives

4.4 Choice of alternatives

With all the alternatives explored it is now possible to combine the alternatives for the

process with the alternatives for the process steps. This gives the following combina-

tions of alternatives;

The order of steps within the process:

• Pre-blasting with mechanical blasting followed by cleaning with laser or dry ice

• Pre-blasting with grit blasting followed by cleaning with laser or dry ice

Combination of steps within the process:

• Shockwave Induced Spray Painting

• Combined Heat & Coat machine with alternative heating coil

Alternative methods within the process step:


• Pick brush instead of grit blasting

• LAT FBE instead of FBE


The most promising alternatives can be found when the requirement found in chap-

ter 2 and chapter 3 are applied.

It can be concluded that the following alternatives are not a possible alternative at

this moment:

• Pre-blasting with grit blasting followed by cleaning with laser or dry

ice. This alternative would transfer the existing problems in the FL with the grit

blaster to the location of pre-blasting.

• Shockwave Induced Spray Painting. This technique has not yet been proven

with the use of FBE. Incorporation of this technique would require more funda-

mental research.

47


• Combined Heat & Coat machine with alternative heating coil. This al-

ternative would require more research into the different shapes of heating coils and

alternative methods of applying FBE. This requires more fundamental research.

• Pick brush instead of grit blasting. From experience with the regular PWB

frame it is known that the brushes must be changed regularly. This means down-

time and lower overall process times. This means that this alternative is not

suited for further research.

4.5 Conclusions

Based on the combined alternatives of the process and the equipment there are a number

of alternatives that should be further researched:





To further asses their possibilities within the FJC process more data is required.

For each of these alternatives it must be know what the process times are and if it

is possible to obtain a quality coating. To acquire this data, practical tests must be

performed. These tests are described in the next chapter.

48

5

Tests

In the previous chapter alternative application methods were pre-selected. The pre-

selection was based on requirements that originated from literature research and in-

terviews with suppliers and Allseas employees. In this chapter these alternatives are

further tested on criteria which where estimated beforehand but can be confirmed with

the help of practical tests.

Section 5.1 describes the goal of the tests. In section 5.2 the method of testing is

explained. In section 5.3 the validation of the tests is discussed. In section 5.4 the

results of the tests are presented. Finally in section 5.5 conclusions are drawn based

on the test results.

5.1 Goal

The goal of the tests is to get an idea of the performance of the alternatives with respect

to the existing FJC process. The research and selection of alternatives was based on

literature and discussions with suppliers. This resulted in a number of claims and ideas.

These can be summarised as follows:

• It is possible to create an anchor profile with laser blasting

• Mechanical blasting is faster than grit blasting

• Two stage blasting results in lower overall process times

• Two stage blasting results in a coating of an acceptable quality level for mechan-

ical pre-blasting and laser cleaning

49

5. TESTS

• Two stage blasting results in a coating of an acceptable quality level for mechan-

ical pre-blasting and dry ice cleaning

• LAT FBE results in a coating of an acceptable quality level

• Dry ice blasting with the addition of grit is faster than grit blasting

• Dry ice blasting with the addition of grit results in a coating of an acceptable

quality level

The main goal of these tests is to see whether these claims hold true or not.

5.2 Method

To reach the goal of these tests a practical test was designed. In this test the actual

process of FJC was replicated as close as possible.

5.2.1 Test subjects

During PQTs whole joints are used or pieces cut from joints. In order to simplify

testing the joints are replaced by flat metal plates. The size of the plates was based on

the standard for laboratory tests as prescribed in ISO norm 21809-2. In the norm the

minimum dimensions of 100 x 100 x 6.3 mm are prescribed. Based on availability of

steel plates for this test, plates with dimensions of 100 x 100 x 8 mm were used. Test

plates were cut from the same plate. This ensures the same grade of steel was used for

all the plates.

The plates were treated to simulate the condition of joints as mentioned in sec-

tion 2.2.1. They were blasted to SA 2.5 to remove the mill scale. They were then

sprayed with water and left outside for the duration of two weeks. During this time

the surface of the plates started to corrode again. This can be seen in figure 5.1

This resembles the condition that joints can be in before entering production. Joints

are sometimes stored for a period of time on a yard before leaving on a supply vessel to

the PLV. This exposes the bare ends of the joint to the elements, resulting in corrosion.

In figure 5.2 the corroded test plates can be seen after the duration of two weeks.

50

5.2 Method

Figure 5.1: Test plates blasted and put outside

Figure 5.2: Corroded test plates

5.2.2 Setup

The test setup was designed and built in-house. Its purpose was to replicate the actual

coating process as close as possible. For a controlled movement the linear motor of

the blast frame was used. This linear motor can be controlled with a control panel.

On the control panel the speed and distance that the motor travels can be set. This

type of control panel is also used during production on the PLVs. The motor is fitted

with a clamp. In this clamp either the nozzle for the application of FBE powder can

be fitted or the grit blaster head. With the FBE nozzle connected the fluidized beds

which control the flow of FBE powder can be switched on and off with the control

panel. With the grit blaster head connected, the LTC grit handling unit is connected

51

5. TESTS

to the panel. The flow of grit can then be controlled. The finished test setup can be

seen in figure 5.3

Figure 5.3: Test setup

To hold the test plates in place a jig was constructed. In this jig the test plate lies

enclosed and an even surface is created. To heat the plates an industrial oven was used.

This temperature of the oven could be set with an accuracy of 1.0 degrees Celsius. The

initial plan for heating the plates was to use an induction cooking plate. Practical

problems with the plate however prevented this, as the plate failed during validation

tests.

5.2.3 Execution

In total nine batches of six plates were made. Each batch underwent the following

steps:

Batch A Current process: grit blasting - heat - FBE

Batch B Current process with delay: Grit blasting - one day delay - heat - FBE

Batch C Current process with LAT FBE: Grit blasting - heat - LAT FBE

Batch D Mechanical blasting - heat - FBE

52

5.2 Method

Batch E Mechanical blasting - FL conditions - laser cleaning - heat - FBE

Batch F Mechanical blasting - FL conditions dry ice cleaning - heat - FBE

Batch G Dry ice + grit blasting - heat - FBE

Batch H Laser (quality) blasting - one day delay - heat - FBE

Batch I Laser (time) blasting - one day delay - heat - FBE

Each of the individual steps was done in a certain manner. Grit blasting was done

in the test setup. The grit blast head could automatically move over the plate in the

X-direction. The Y-direction was manually controlled by an operator. Air pressure

was set at 8 bars. Figure 5.4 shows the grit blast head fitted in the test setup.

Figure 5.4: Grit blast head fitted in test setup

Heating was done in the oven. For normal FBE the oven was set at 240 degrees

Celsius. For LAT FBE the oven was set at 190 degrees Celsius. Plates were then put

in the oven for 15 minutes. When placed in the coating frame, test plate temperatures

were then 230 degrees Celsius for the normal FBE batch. For the LAT FBE batch the

test plate temperature was 180 degrees Celsius. In figure 5.5 the plates can be seen

laying in the oven.

FBE and LAT FBE application was done in the test setup. In figure 5.6 the FBE

powder application nozzle can be seen as fitted in the test setup. The heated test plates

were placed in the jig in the test setup. The FBE nozzle was moved automatically over

53

5. TESTS

Figure 5.5: Test plates in industrial oven

the test plate. Settings of the fluidised beds were the same as during production (2.5

bars). The nozzle made four passes over the plate. Plates were taken out of after 60

seconds with a spatula. They were then placed on racks for further curing.

Figure 5.6: FBE application nozzle fitted in test setup

One day delay is explained in section 5.3.2

Mechanical blasting was done by manually moving the machine over plate. The test

plate was placed in the jig. The mechanical blaster then made one pass back and forth

over the test plate. The test plate was then turned 180 degrees and again one pass

54

5.2 Method

back and forth was made. The jog was turned because of two reasons. The throwing

wheel propels the blast media to one side due to layout of the wheel and the direction

it spins. To guarantee both edges of the test plate receive the same treatment the jig

was turned. The jig and mechanical blaster can be seen in figure 5.7.

Figure 5.7: Mechanical blaster test setup

FL conditions were a simulation of the effects of heating the pipe during welding

and cooling it again with NDT coupling water. With two-stage blasting the FJ is prone

to corrosion between the first and the second blast step. It was expected that the NDT

water would induce the corrosion process. This was simulated by heating the test plates

in the oven to 90 degrees Celsius. Then they were sprayed with water and laid to rest

for the duration of 10 minutes. This can be seen in figure 5.8.

Dry ice cleaning was done manually. The dry ice blast gun was manually moved

over the test plate. The test plate was fitted in the jig. Air pressure was set at 8 bars.

For the dry ice plus grit surface treatment the blast gun was manually moved over

the test plate. The test plate was fitted in the jig. Air pressure was set at 8 bars. The

valve controlling the feed of Cryosand was opened halfway. In figure 5.9 the method of

dry ice blasting can be seen.

Each of the three variants of laser treatment were done one the same machine.

The test piece was placed in a jig with a set distance to the laser as can be seen in

figure 5.10. The laser was set to certain settings for each of the three variants. For the

leaser cleaning the fastest speed was used. For laser quality the laser was set to make

55

5. TESTS

Figure 5.8: Simulating FL conditions with heat and NDT water

an anchor profile of 100 micrometre. For the laser time variant the laser was set to

make a lower anchor profile and thus aiming for a faster cycle time.

5.2.4 Measurements

During tests the following measurements were taken using the following equipment:

Pre-test:

• Temperature - Fluke thermometer

• Dew point - Elcometer dew point meter

Surface preparation noise level (safety):

• Surface cleanliness - Elcometer 125 Surface Comparator

• Surface profile - Testex tape with Elcometer micrometre

• Time - Stopwatch

56

5.2 Method

Figure 5.9: Dry ice blasting method

Figure 5.10: Laser treatment test setup

• Noise - Rion NL20 noise level meter

Coating application:

• Temperature - Fluke thermometer

• Coating thickness - Elcometer 456 thickness meter

57

5. TESTS

Destructive tests:

• Adhesion - tape measure

• Pull-off force - Elcometer 506 pull-off tester

5.3 Validation

Before the main tests a number of validation tests have to be performed to check

whether the test devices and methods are performing as expected. Next to that some

batches were made only for comparison reasons.

5.3.1 Setup

Extra test plates used to test the test setup:

• Set grit blaster (speed, position)

• Set mechanical blaster (speed, position)

• Coating thickness

• Pre-set temperature of the oven

• Cooling (cure) of test plate

Once the test setup was working two batches of plates were done. These batches

were:

• Mechanical blasting

• Grit blasting

Both batches act as the baseline measurement. The other batches can be compared

against them.

58

5.4 Results

5.3.2 Delay

Three batches of test plates were laser blasted. This could not be done at the test site

in IJmuiden but was done at SLCR in Germany. Because of practical reasons it was

not possible to coat the plates directly after laser blasting. This was done the next day.

It was expected that this delay would have negative effects on the surface. If moisture

or other contaminates come in contact with the surface, the corrosion process could

start.

To minimize these effects the plates were individually wrapped in aluminium foil.

This was also the practice of SLCR if they would have to ship laser blasted samples.

The batch was then packed in thick PE bags which were sealed. To eliminate moisture,

sachets of silica gel were also put in the bag.

To check whether this delay affects coating quality, a batch that was grit blasted

was treated in the same manner. The batch was grit blasted, packed and put aside for

24 hours. After 24 hours it was heated and coated.

5.4 Results

The results of the measurements and the quality tests are given in the next sections.

The results are split up in tree blocks; Surface preparation, coating application and

destructive tests.

5.4.1 Surface preparation

These measurements were taken during surface preparation.

Cleanliness

Cleanliness cannot actually be measured. It is assessed with the Elcometer 125 Surface

Comparator. This disc has four different samples of surface cleanliness conditions. The

disc is hold against the treated surface. The one closest to the actual surface condition

gives the measured value. In figure 5.11 the assessment of a mechanical blasted test

plate can be seen.

For each of the surface preparations, the surface cleanliness could be compared to

SA 2.5 in my opinion. Exemptions are the two laser treatments (quality and time). I

was not able to make a good comparison with either of the samples on the disc.

59

5. TESTS

Figure 5.11: Surface comparator with mechanical blasted test plate

Because of the subjective nature of this test the results must be seen as indicative

results. This test was done for the sake of comparison between the different surface

treatment alternatives.

Anchor profile

The anchor profile after each of the surface treatments was measured with Testex tape

and an Elcometer micrometre. The Testex tape was rubbed against the treated surface.

This leaves an indentation in the tape. This indentation is the height of the surface

profile. This height can be measured by pressing the Testex tape in the Elcometer

micrometre as can be seen in figure 5.12. The measurements are given in table 5.1.

Because of the limited availability of Testex tapes during tests it was only possible

to do one measurement per batch. The measured values therefore must be interpreted

is indicative results.

A visual inspection of the treated surfaces showed an interesting comparison be-

tween the surfaces treated with grit and those with laser. Laser treatment gives a very

ordered anchor profile as can be seen in figure 5.14. The other methods show a chaotic

(random) profile. An example of this can be seen in figure 5.13.

60

5.4 Results

Surface treatment [microns]

Grit blasting 100

Mechanical blasting 80

Dry ice cleaning 70

Laser cleaning 74

Dry ice with grit blasting 68

Laser blasting (quality) 100

Laser blasting (time) 65

Maximum allowable 100

Minimum allowable 32

Table 5.1: Anchor profile measurements

Figure 5.12: Measuring of the Testex tape

Time

During each of the surface preparation methods the time was monitored. Because each

of the test plates has the same dimension, the times can be compared. In table 5.2 the

times are given.

Noise

Because of QHSE requirements the noise levels for each of the surface treatment meth-

ods was measurement. Noise level measurements during laser treatment were not taken

61

5. TESTS

Figure 5.13: Surface after mechanical blasting

Figure 5.14: Surface after laser blasting

as this method produces no abnormal noise levels. During laser tests no hearing pro-

tection was needed. The results can be seen in table 5.3.

Noise levels where measured from a distance of 1.0 meter as can be seen in fig-

ure 5.15. With respect to the result of the dry ice measurements a remark must be

made. There was no suction brush surrounding the nozzle as is the case with the grit

blaster. It could be possible that this would have a dampening effect. For safety reasons

it was not possible to measure the grit blaster without the brush or the dry ice nozzle

with a brush.

62

5.4 Results

Surface treatment T[sec] [m2/hr] [hr/m2] [min/m2]

Grit blasting 21 1.71 0.58 35

Mechanical blasting 68 0.53 1.89 113

Dry ice cleaning 36 1.00 1.00 60

Laser cleaning 20 1.80 0.56 33

Dry ice with grit blasting 14 2.57 0.39 23

Laser blasting (quality) 187 0.19 5.19 312

Laser blasting (time) 94 0.38 2.61 157

Table 5.2: Cycle time measurements

Surface treatment dB

Grit blasting 108

Mechanical blasting 98

Dry ice cleaning 112

Dry ice with grit blasting 117

Table 5.3: Noise level measurements

Figure 5.15: Test setup Noise level measurement

5.4.2 Coating application

The following measurements were taken directly after coating application.

Observation

According to ISO 21809-2 the coating must look uniform, feel smooth and free of

orange peel. This was the case for all the batches. This was checked and confirmed by

63

5. TESTS

experienced coating applicators on site. An example can be seen in figure 5.16

Figure 5.16: Cured coating on a test plate

Thickness

The coating thickness was measured for every plate. Measurements were taken on 9

points per plate. The average of all the measurement per batch is given in table 5.4.

Batch [microns]

A: Current process 426

B: Current process with delay 444

C: Current process with LAT FBE 414

D: Mech blasting 392

E: Pre-blast mech + laser cleaning 476

F: Pre-blast mech + dry ice cleaning 443

G: Dry ice with grit blasting 458

H: Laser blasting (quality) 453

I: Laser blasting (time) 456

Maximum allowable 500

Minimum allowable 300

Table 5.4: Dry film thickness measurements

Measurements were taken with the Elcometer 456 thickness meter. The meter was

64

5.4 Results

calibrated before use.

5.4.3 Destructive tests

After the coating of all the batches was fully cured, the quality of the coating was tested

with destructive tests. The tests were done in the below presented order.

Adhesion

The adhesion test is a test from ISO norm 21809-3. Two cuts were made in the coating

with a sharp knife. These two cuts have to form an X with an angle of approximately 30

degrees at the intersection point. A levering action with the knife was then performed

at the intersection of the cuts. The knife was used to try to prise the coating off. In

figure 5.17 an example of the adhesion test on one of the plates is given. The amount

of coating that came of was then measured. For each batch this test was performed on

two different plates. This was done three times per plate. For all of the batches the

amount of coating that came loose was no less than 2mm. All batches therefore were

considered as a pass.

Figure 5.17: Adhesion test - resistance to removal

65

5. TESTS

Pull-off

Pull-off tests were performed with the Elcometer 506 pull-off tester. During a pull-off

test aluminium dollies are glued to the coating. A device then tries to pull off the dolly.

In figure 5.18 the pull-off tester and dollies can be seen.

Figure 5.18: Pull-off tester and 20mm dollies glued to test plate

If the dolly cannot be pulled of when a minimum amount of 10 MPa of pulling force

is exerted on the dolly it is considered a pass. Of the glue fails below 10 MPa the test

is invalid. If the coating fails below 10 MPa, the coating is of bad quality. Of all the

coating comes loose with the dolly it is called an adhesion failure. Table 5.5 gives the

results for the pull-off tests with 20mm dollies.

For all measurements there was a glue failure. But al pull-off force measurements

were above 10 MPa. Based on these results all coatings can be considered a pass.

66

5.4 Results

Batch MPa

A: Current process 24.5

B: Current process with delay 14.0

C: Current process with LAT FBE 23.0

D: Mech blasting 18.5

E: Pre-blast mech + laser cleaning 20.5

F: Pre-blast mech + dry ice cleaning 17.5

G: Dry ice with grit blasting 14.3

H: Laser blasting (quality) 19.5

I: Laser blasting (time) 17.3

Minimum required 10.0

Table 5.5: 20mm dolly pull-off test measurements

Because there was only one pull-off test done per batch these results must be interpreted

as indicative results.

To gather more results 14mm dollies were also used to perform pull of tests. With

these dollies a better quality adhesive was used in order to see if a coating or adhesion

failure could be found. With 14mm dollies it was possible for the pull-off device to

exert more pulling force. The results of these tests can be seen in table 5.6.

(c=coating, a=adhesive, m=mix) mid 2 3

Batch MPa fail MPa fail MPa fail

A: Current process 31.5 c 42,5 c 41,0 m

B: Current process with delay 36.0 c 36.5 c 37.0 c

C: Current process with LAT FBE 45.5 c 48.0 a 48.0 a

D: Mech blasting 48.0 c 47.5 a 40.0 m

E: Pre-blast mech + laser cleaning 26.0 c 35.5 c 36.0 c

F: Pre-blast mech + dry ice cleaning 34.5 c 42.0 c 32.0 c

G: Dry ice with grit blasting 30.0 c 38.0 c 39.5 m

H: Laser blasting (quality) 35.0 c 42.0 c 37.0 c

I: Laser blasting (time) 48.0 m 47.0 a 47.5 m

Minimum required 10.0 10.0 10.0

Table 5.6: 14mm dolly pull-off test measurements

67

5. TESTS

From the results it can be seen that not a single pull-off was below the minimum

pull-off force of 10 MPa. Also none of the tests were a failure of adhesion between

substrate and coating. Therefore it can be concluded that based on these measurements

all coatings can be considered a pass.

During the 14mm pull-off tests three failure types were reached on a single test

plate. These can be seen in figure 5.19. Because these failures were not am adhesion

failure en the exerted pull-off force was well above the minimum of 10 MPa this plate

was also considered a pass.

Figure 5.19: Pull-off results 14mm: three failure types for batch D

Cathodic disbondment

CD tests were performed by Element in Amsterdam. Element is an independent test

lab. To test the cathodic disbondment the procedure as described in ISO 21809-3

Annex C has been followed.

A hole was drilled in the centre of the test plate through the coating. A plastic

cylinder was then glued onto the plate. The cylinder was filled with a solution of 3

% sodium chloride in distilled water. A 0.8 mm. platinum wire electrode was hanged

68

5.4 Results

in the cylinder above the drilled hole. The plate itself was earthed to a power supply

which put a voltage of 3.5 V on the platinum electrode. The setup then was heated

to 65 degrees Celsius and kept in that state for 24 hours. The setup with all the nine

plates can be seen in figure 5.20.

Figure 5.20: Cathodic disbondment test setup at Element, Amsterdam

After the period of 24 hours the plates were taken out and all the equipment was

removed. Then 8 cuts were made with a sharp knife. The knife was used to try to prise

the coating off. In figure 5.21 the disbondment of the coating of one of the plates can

be seen.

According to the ISO norm no more than an average of 8 mm. of coating should

come loose. This is measured from the edge of the drilled hole to the edge of the

remaining coating. The results can be seen in table 5.7. It can be seen that al plates

are well below the maximum allowable loss of coating. However the results must be

interpreted as indicative results, as the CD test was performed on just one test plate

per batch.

69

5. TESTS

Figure 5.21: Cathodic disbondment on test plate

Batch [mm]

A: Current process 1.250

B: Current process with delay 1.625

C: Current process with LAT FBE 1.000

D: Mech blasting 0.125

E: Pre-blast mech + laser cleaning 0.125

F: Pre-blast mech + dry ice cleaning 1.125

G: Dry ice with grit blasting 1.000

H: Laser blasting (quality) 0.125

I: Laser blasting (time) 0.000

Maximum allowable 8.000

Table 5.7: Cathodic disbondment test results

5.5 Conclusions

To conclude this chapter the most important test results are summarised in table 6.1.

On the basis of the summarised test results a number of conclusions can be drawn;

• All of the processes resulted in a coating with a quality level that passed the tests.

• The delay of one day did not have an effect on the passing of the quality level

tests.

70

5.5 Conclusions

• For all surface preparation methods it was possible to create an anchor profile of

at least 32 microns.

• It was possible to create an anchor profile with laser blasting, but this took a

longer time than with any of the other surface preparation methods.

• Cleaning with dry ice takes a longer time than grit blasting and the noise level is

higher

• Dry ice blasting with grit takes a shorter time than grit blasting but the noise

level was the highest of all the surface preparation methods.

Anchor Noise Capacity Dry film Quality

Batch [microns] [dB] [min/m2] [microns]

A: Current process 100 108 35 426 pass

B: Current process with delay 100 108 35 444 pass

C: Current process with LAT FBE 100 108 35 414 pass

D: Mech blasting 80 98 113 392 pass

E: Pre-blast mech + laser cleaning 74 98 33 476 pass

F: Pre-blast mech + dry ice cleaning 70 112 60 443 pass

G: Dry ice with grit blasting 68 117 23 458 pass

H: Laser blasting (quality) 100 - 312 453 pass

I: Laser blasting (time) 65 - 157 456 pass

Table 5.8: Test results summarised

Regarding the scale of the test equipment there are some remarks to be made with

respect to the obtained test results. For mechanical blaster a longer time was needed

to clean the test piece than with grit blasting. The mechanical blaster however was

a small scale test unit, where the grit blaster was the full scale unit as used during

production. For the actual use in production a larger mechanical blast setup could be

obtained. According to the supplier of such equipment it is possible to create an anchor

profile in a shorter time than with grit blast equipment. This should be verified with

tests using such equipment.

For laser blasting a similar remark can be made. During tests a laboratory scale

laser was used. For actual production higher powered laser equipment is available.

According to the supplier of this equipment faster process times than those of the test

should be available. This however should be verified with test using such equipment.

71

5. TESTS

The use of LAT FBE resulted in a coating of a level that passed the quality tests.

Because an industrial oven was used it was not possible to get data regarding process

times, which could be used for comparison. A lower overall process time can be expected

with the use of LAT FBE. Exact data should be verified with further tests using a

heating coil, which would make comparison possible.

Based on the above conclusion and with the mentioned remarks in mind there are

three processes that can be identified as possible alternatives for the application process

of FBE as field joint coating:

• Mechanical pre-blasting followed by cleaning with laser in the FL

• Dry ice with grit blasting in the FL

• The use of LAT FBE

These alternatives could lead to lower overall process times while maintaining the cur-

rent quality level of coating.

72

6

Conclusions & Recommendations

In this closing chapter all the conclusion that were made during the research are gath-

ered and summarised. The conclusions are presented in section 6.1. Based on the

conclusions a number of recommendations can be made. They are given in section 6.2.

6.1 Conclusions

From the analysis of the current method of pipeline production it was concluded that

there are three possibilities for changes to the process that could have an effect on the

overall process time.




From the analysis of the equipment used for FJC application of FBE a number of

conclusions were drawn.

For surface preparation grit blasting is an effective method for reaching the de-

sired anchor profile and cleanliness. However there are a number of possibilities for

improvements:

• Noise level of the grit blaster

• Usage of consumables (blast media)

73

6. CONCLUSIONS & RECOMMENDATIONS

• The required space for supporting equipment (LTCs)

Regarding the heating of the FJ, the principle of induction heating is the most

suitable. A possibility for change could lie in the shape of the coil. If the shape of the

current induction coil could be changed it could be possible to combine the coil with

other process steps.

Based on the combined alternatives of the process and the equipment it was con-

cluded that there are a number of alternatives that should be further researched:





The combined alternatives where further researched with practical tests. The test

results are summarised in table 6.1.

Anchor Noise Capacity Dry film Quality

Batch [microns] [dB] [min/m2] [microns]

A: Current process 100 108 35 426 pass

B: Current process with delay 100 108 35 444 pass

C: Current process with LAT FBE 100 108 35 414 pass

D: Mech blasting 80 98 113 392 pass

E: Pre-blast mech + laser cleaning 74 98 33 476 pass

F: Pre-blast mech + dry ice cleaning 70 112 60 443 pass

G: Dry ice with grit blasting 68 117 23 458 pass

H: Laser blasting (quality) 100 - 312 453 pass

I: Laser blasting (time) 65 - 157 456 pass

Table 6.1: Test results summarised

On the basis of the summarised test results a number of conclusions were drawn;

• All of the processes resulted in a coating with a quality level that passed the tests.

• The delay of one day did not have an effect on the passing of the quality level

tests.

74

6.2 Recommendations

• For all surface preparation methods it was possible to create an anchor profile of

at least 32 microns.

• It was possible to create an anchor profile with laser blasting, but this took a

longer time than with any of the other surface preparation methods.

• Cleaning with dry ice takes a longer time than grit blasting and the noise level is

higher

• Dry ice blasting with grit takes a shorter time than grit blasting but the noise

level was the highest of all the surface preparation methods.

The final conclusion of this research should answer the research question as stated in

chapter 1: ’What are the possibilities to change the current process of field joint coating

application, in order to achieve faster cycle times while maintaining the current coating

quality, while taking into account requirements for changes to the process?’

Three alternatives can be identified as possible alternatives for the application pro-

cess of FBE as field joint coating that could lead to lower overall process times while

maintaining the current coating quality:

• Mechanical pre-blasting followed by cleaning with laser in the FL

• Dry ice with grit blasting in the FL

• The use of LAT FBE

6.2 Recommendations

Before the alternatives for FJC application can be implemented more research is needed.

First a research should be conducted into which of these three alternatives would be

the most promising or worthwhile to pursue.

For each of the separate alternative methods a number of further research topics

can also be identified;

Mechanical pre-blasting followed by cleaning with laser in the FL:

• Research the possibilities for the incorporation of a mechanical blaster in the

bevelling station

75

6. CONCLUSIONS & RECOMMENDATIONS

• Further test the use of laser equipment in the current process and with the current

equipment

• Investigate possible safety issues related to the use of laser equipment

Dry ice with grit blasting:

• Research the logistics of dry ice pellets

• Research the possibility of producing of dry ice on board the vessels

• Execute more tests with different types of blast media added to the dry ice

• Research the possibilities for the reduction of noise levels

• Investigate the possible safety issues with CO2

The application of LAT FBE:

• Research the possible time reduction when applying LAT FBE with current equip-

ment

• Research the cost aspect of applying LAT FBE powder with respect to the re-

duction of time (cost versus gain)

76

Bibliography

[1] Norton Sandblasting Equipment. Norton coroporate website, 2013. URL http:

//www.nortonsandblasting.com/nsbabrasives-anchr.html. xi, 25

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http://www.nortonsandblasting.com/nsbabrasives-anchr.html

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79

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