6 Coating of Steel Structures...Hydroblasting and Coating of Steel Structures.. potx

6 Coating of Steel Structures

Hydroblasting and Coating of Steel Structures

H yd rob I ast i ng

and Coating of

Steel Structures

Andreas W. Momber

Privatdozent, Department of Mining,

Metallurgy and Earth Sciences,

RWTH Aachen Germany

ELSEVIER

UK

USA

JAPAN

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Cover illustration: Courtesy of Muhlhan Surface Protection International GmbH,

Hamburg, Germany

British Library Cataloguing in Publication Data

Momber, Andreas W., 1959-

Hydroblasting and coating of steel structures

1.Water jet cutting 2.Stee1, Structural - Cleaning

3.Building, Iron and steel - Cleaning

1.Title

620.1’06

ISBN 185617395X

Library of Congress Cataloging-in-Publication Data

Momber, Andreas W., 19 59 -

Hydroblasting and coating of steel structures / Andreas W. Momber

Includes bibliographical references and index.

ISBN 1-85617-395-X (hardcover)

p. cm.

1. Steel, Structural - Corrosion. 2. Corrosion and anti-corrosives.

I. Title.

TA467 .M545 2002

620.1’723 -dc2 1 2002040768

No responsibility is assumed by the Publisher for any injury andlor damage to

persons or property as a matter of products liability, negligence or otherwise, or

from any use or operation of any methods, products, instructions or ideas contained

in the material herein.

Published by

Elsevier Advanced Technology,

The Boulevard, Langford Lane, Kidlington, Oxford OX5 lGB, UK

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Typeset by Newgen Imaging Systems (P) Ltd, Chennai, India

Printed and bound in Great Britain by Biddles Ltd, Guildford and King’s Lynn

Contents

List of Symbols and Abbreviations Used

1 Introduction

1.1 Definitions of surfaces and preparation methods

1.2 Importance of surface preparation processes

1.3 Subdivision of water jets

1.4 Industrial applications

2 Fundamentals of Hydroblasting

2.1 Properties and structure of high-speed water jets

2.2 Basic processes of water drop impact

2.3 Parameter influence on the coating removal

2.4 Models of coating removal processes

3 Hydroblasting Equipment

3. I

3.2 Pressure generator

3.3 High-pressure hoses and fittings

3.4 Hydroblasting tools

3.5 Nozzle carriers

3.6 Hydroblasting nozzles

3.7 Vacuuming and water treatment systems

High-pressure water jet machines

4 Steel Surface Preparation by Hydroblasting

4.1 Efficiency of hydroblasting

4.2 Cost aspects

4.3 Problems of disposal

4.4 Safety features of hydroblasting

5 Surface Quality Aspects

5.1 Surface quality features

5.2 Adhesion strength

5.3 Flash rust

5.4 Non-visible contaminants - salt content

vii

17

18

24

29

38

45

46

47

55

59

63

66

73

77

78

84

87

94

113

114

114

121

126

vi Contents

5.5 Embedded abrasive particles

5.6 Wettability of steel substrates

5.7 Roughness and profile of substrates

5.8 Aspects of substrate surface integrity

6 Hydroblasting Standards

6.1 Introduction

6.2 Initial conditions

6.3

6.4 Non-visible surface cleanliness definitions

6.5 Flash rusted surface definitions

6.6 Special advice

Visual surface preparation definitions and cleaning degrees

7 Alternative Developments in Hydroblasting

7.1 Pulsed liquid jets for surface preparation

7.2 Hydro-abrasive jets for surface preparation

7.3 High-speed ice jets for surface preparation

7.4 Water jethltrasonic device for surface preparation

References

133

136

138

144

149

150

151

152

154

155

157

159

160

169

176

181

183

Appendix 199

Index 203

~ ~

List of Symbols and

Abbreviations Used

model parameter

jet structure parameter

cleaned surface

cleaning rate

nozzle (orifice) cross section

plunger cross section

jet structure parameter

fatigue parameter

cleaning energy flux

speed of sound water

constant

speed of sound target

paint consumption

jet spreading coefficient

paint degradation rate

drop diameter

maximum drop diameter

Sauter diameter (water drop)

dry film thickness

hose diameter

jet diameter

nozzle (orifice) diameter

plunger diameter

threshold nozzle diameter

cleaning effectiveness

kinetic energy hydro-abrasive jet

cleaning efficiency

kinetic energy water jet

Young’s modulus

kinetic energy abrasive particle

specific energy

frequency pulsating liquid jet

viii List of Symbols and Abbreviations Used

plunger rod force

reaction force

acceleration due to gravity

erosion depth

erosion rate

geodetic height

coating thickness

micro hardness

stroke

erosion intensity

jet impulse flow

internal roughness

damage accumulation parameter

hose length

coating performance life

abrasive mass flow rate

coating mass loss rate

mass loss coating material

model parameter

solid mass

water mass flow rate

life cycle (fatigue) number

crank-shaft speed

drop number

plunger number

cleaning steps

Ohnesorge number

pressure

atmospheric pressure

power density water jet

hydraulic power

cavitation pressure

jet power

optimum pressure

stagnation pressure

theoretical hydraulic power

threshold pressure

pressure loss

actual volumetric flow rate

loss in volumetric flow rate

nominal volumetric flow rate

volumetric flow rate water

erosion resistance parameter

rust rate

specific disposal rate

Re Reynolds number

List of Symbols and Abbreviatios Used ix

ZC

ZF

rust grade

mixing ratio

pressure ratio

substrate roughness factor

radial distance nozzle-rotational centre

paint lifetime parameter

erosion strength

Strouhal number

surface preparation parameter

solid by volume (paint)

water jet velocity standard deviation

exposure time

blasting time

nozzle down time

interface fracture energy

impact duration

turbulence

working time

theoretical jet velocity

abrasive particle velocity

crank-shaft circumferential velocity

drop velocity

flow velocity

jet velocity

average jet velocity

nozzle (orifice) flow velocity

average plunger speed

traverse rate

water consumption

cleaning width

Weber number

jet length: stand-off distance

critical stand-off distance

water jet core length

water jet transition zone length

traverse parameter

acoustic impedance coating

acoustic impedance water

acoustic impedance substrate

hose pressure loss

power loss

coating thickness parameter

impedance ratio

nozzle (orifice) flow parameter

erosion response parameter

abrasive mixing efficiency parameter

x List of Symbols and Abbreviations Used

crank-shaft angle

gas content

model parameter

paint loss correction factor

DFT conditioning factor

efficiency parameter

impact angle

model parameter

pump efficiency

kinematic viscosity water

hydraulic efficiency

mechanical efficiency

transmission efficiency

model parameter

model parameter

stress coefficient

mode1 parameter

nozzle (orifice) efficiency parameter

Poisson’s ratio coating

dynamic viscosity water

contact angle

model parameter

nozzle (orifice) angle

coating density

density air

density target

density liquid

average surface stress

impact stress (water hammer pressure)

surface tension water

endurance limit coating material

ultimate strength

rotational speed

compressibility parameter

hose friction number

volume loss parameter

CHAPTER 1

I n t rod u ct ion

1.1

1.2

1.3 Subdivision of Water Jets

Definitions of Surfaces and Preparation Methods

Importance of Surface Preparation Processes

1.3.1 Definitions and Pressure Ranges

1.3.2 Fluid Medium and Loading Regime

1.4.1 General Statement

1.4.2 Industrial Cleaning

1.4.3 Civil and Construction Engineering

1.4.4 Environmental Engineering

1.4 Industrial Applications

2 Hydroblasting and Coating of Steel Structures

1.1 Definitions of Surfaces and Preparation Methods

Surface preparation processes affect performance and lifetime of coating systems

significantly. Surface preparation is defined in IS0 12944-4 as ‘any method of

preparing a surface for coating.’ Surface preparation is an important part of any

steel corrosion protection strategy. This is illustrated in Fig. 1.1 which shows major

factors for the selection of a corrosion protection system.

A surface that is prepared for painting or coating is usually denoted ‘substrate’.

A definition for substrate is: ‘The surface to which the coating material is applied or

is to be applied.’ (IS0 12944-1). Therefore, a substrate is generally generated from an

existing surface. A substrate is a prepared or treated surface. Surfaces that are pre￾pared by different methods include the following types (IS0 12944-4):

(i) Uncoated surfaces

Uncoated surfaces consist of bare steel, which may be covered by mill scale

or rust and other contaminants. They will be assessed in accordance with

IS0 8501-1 (rust grades A, B, C and D).

0 surfaces thermally sprayed with zinc, aluminium or their alloys;

0 hot-dip-galvanised surfaces:

0 zinc-electroplated surfaces:

0 sherardised surfaces.

Surfaces painted with prefabrication primer

Surfaces painted with prefabrication primer consist of automatically blast￾cleaned steel to which a prefabrication primer has been applied automati￾cally in a plant.

(iv) Other painted surfaces

Other painted surfaces consist of steel/metal-coated steel which has

already been painted.

(ii) Metal-coated surfaces

(iii)

Local demands

Protective coating system

Figure I. 1 Evaluation process for a protective coating system (Pietsch and Kaisel: 2002).