Hydroblasting and Coating of Steel Structures 2011 Part 1 docx

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 Elsevier Ltd, The Boulevard, Langford Lane, Kidlington, Oxford OX5 lGB, UK Elsevier Inc, 360 Park Avenue South, New York, NY 10010-1710, USA Elsevier Japan, Tsunashima Building Annex, 3-20-1 2 Yushima, Bunkyo-ku, Tokyo 1 13, Japan Copyright 0 2003 Elsevier Science Ltd. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing 6-om the publishers. 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 Tel: +44(0) 1865 843000 Fax: +44(0) 1865 843971 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 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 [...]... be used for firmly adhering rust Residuals of dust and loose deposits will have to be removed 4 Hydroblasting and Coating of Steel Structures Table 1. 1 Continued ~~ Procedure Remarks’ Water blast-cleaning Matter to be removed For removal of loose rust The surface profile of the steel is not affected For localised removal of rust Spot blast-cleaning Paint coatings Stripping Dry abrasive blast-cleaning... 1. 2 Hydroblasting is denoted as water blast-cleaning (marked in Fig 1. 2) in terms of IS0 12 944-4, and is defined as follows: ‘This method consists in directing a jet of pressurised clean, fresh water on to the surface to be cleaned The water pressure depends on the contaminants to be removed, such as water-soluble matter, loose rust and poorly adhering paint coatings.’ 6 HydrobJasting and Coating of. .. (Adamson, 19 98) Of particular interest are the parameters SI? mD and nLbecause their values depend on surface preparation standard and quality Degradation rate basically depends on surface preparation standard as follows: D l/SPmD (1. 3) Here, the term (1+ mD)is neglected Lifetime depends on surface preparation standard according to a simplified function: where C, summarises other parameters Three levels of. .. Table 1. 3 Surface preparation indices (Adamson, 19 98) Surface preparation Designation Indices SSPC-SPINACE Near-white blast Commercial blast Power tool IS0 nL SP 10 INACE 2 SP 6INAcE 3 SP 3 Sa 2.5 Sa 2 St 3 0 0.5 0 -0.07 1. 35 -0.35 mV Introduction 7 m Z \\ C r n C - Y \ c \ L OO 6 3 10 Cleaning degree SP (SSPC) Figure 1. 3 Surface preparationparametersfor Eqs (1. 1) +1. 4) 3 Organic zinc coating 7 Epoxy coatings... Definitions and subdivisions of steel surface preparation methods are listed in IS0 12 944-4 (19 98) Basically, the following three principal surface preparation methods can be distinguished: (i) (ii) (iii) water, solvent and chemical cleaning: mechanical cleaning including blast-cleaning: flame cleaning Typical cleaning operations performed with these methods are listed in Table 1. 1 Table 1. 1 Procedures... Epoxy coatings I SP-3 ~ SP -10 1 SP-2 mill scale Surface condition Figure 1. 4 Effect of surface quality on corrosion protection (Kogler et al., 19 95) preparation level increases Figure 1. 4,taken from an independent reference, verges these results The average percentage of rusting decreases notably if the quality of surface preparation improves Vocational training in the area of corrosion protection spends... SP 10 (near white), SP 6 (commercial blast) and SP 3 (power tool cleaning) Note that cleaning intensity increases as the number for 'SP' increases Exponential indices nL (for lifetime estimation) and mD (degradation rate) are assigned according to these quality levels The relationships are explained in Table 1. 3 The power functions included in Eqs (1. 1)- (1. 4) are graphically illustrated in Fig 1. 3... lifetime increases and degradation rate decreases if surface preparation standard increases These results of preliminary calculations illustrate the importance of a high-quality surface preparation for coating performance These model calculations are verified through experimental results presented in Fig 1. 3 where a substantial improvement in corrosion protection performance of two coating systems can... Coating of Steel Structures A first approximation of paint degradation rate is obtained using the following equation: The performance life of a coating system in years for a given environment for a designated rust grade of RG = 4.5, can be calculated using the following approach: Both equations are rather complex in structure and certain classified information is required to solve them Most of this information... Rinse with fresh water For removal of poorly adhering paint coatings Ultra-high-pressure (X70MPa) cleaning may be used for firmly adhering coatings For roughening coatings or removal of the outermost coating layer For localised removal of coatings Sweep blast-cleaning on zinc may be performed with aluminium oxide (corundum), silicates or olivine sand 5 % (m/m) ammonia solution in combination with a synthetic-fabric . surface preparation References 13 3 13 6 13 8 14 4 14 9 15 0 15 1 15 2 15 4 15 5 15 7 15 9 16 0 16 9 17 6 18 1 18 3 Appendix 19 9 Index 203 viii List of Symbols and Abbreviations Used plunger. 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. content vii 17 18 24 29 38 45 46 47 55 59 63 66 73 77 78 84 87 94 11 3 11 4 11 4 12 1 12 6 vi Contents 5.5 Embedded abrasive particles 5.6 Wettability of steel substrates