READOS / Manufacturing / KEVOS® original book
Weld Repairs That Hold
Shrinkage, sequence and evidence for repairing steel plate, from the 1919 locomotive firebox to modern pressure equipment
Plan weld repairs to steel plate around damage assessment, shrinkage, joint preparation, sequence, preheat, patches, inspection and a repair record that others can check.
Start readingAbout this book
A weld repair is a second manufacturing process applied to a part that has already lived a life. The plate has been heated, loaded, corroded and sometimes repaired before. A sound repair therefore begins with the damage and its cause, not with the welding torch, and ends with evidence that someone other than the welder can check.
This book is built around an unusual historical source: Airco Welding of Locomotive Fireboxes, a 1919 booklet from the Air Reduction Sales Company of New York. It describes how railway shops replaced riveted firebox seams with oxyacetylene welds, set in patches, closed cracks between staybolt holes and built up edges worn by caulking and corrosion. Its methods were written for a particular era, process and regulatory setting. Its engineering instincts, however, still repay study: weld in short steps that work back towards the finished joint, open the root so the weld penetrates, heat the surrounding plate so it can shrink with the weld, shape patches so their edges avoid rows of holes, and replace a sheet rather than weld one that is cracked everywhere.
Each chapter takes one of those instincts, explains the physics behind it in modern terms and asks what current practice adds. A fictional modern case runs beside the history: a restoration workshop repairing a cracked 10 mm carbon steel side plate of an atmospheric water tank. The tank, its dimensions, compositions, measurements and results are invented for teaching. They are not KEVOS® projects or claims.
What this book is and is not
The booklet’s procedures are discussed as history. They are not instructions for repairing any boiler, pressure vessel or locomotive today. Fireboxes and boilers are pressure equipment. In Australia, their design, repair, inspection and operation are governed by standards, by state and territory work health and safety regulators and, for operating railways, by the national rail safety regulator. Any repair to such equipment requires qualified procedures, qualified welders, competent inspection and the approvals the owner’s regulator and inspection body require.
Calculations use metric units, with the booklet’s imperial dimensions converted where they help. The thermal and shrinkage models are simplified and explicitly limited. Use them to understand why a repair behaves as it does and to ask better questions of procedures, inspectors and engineers.
An original treatment
READOS already introduces welded joints, pressure vessels and corrosion protection in overview chapters, including welded joints for fabricators. This book concentrates on repair: assessing damage, controlling shrinkage, sequencing, patching and documenting. The explanations, the tank case and all worked examples are original KEVOS® writing. The 1919 booklet is a public historical document; its procedures are summarised and analysed in new words, and none of its text or drawings is reproduced.
Who this book is for
Maintenance engineers, fabricators, welding supervisors, inspectors and heritage restorers who must decide how a damaged steel plate structure is repaired, and show why the repair can be trusted.
What you will learn
- Assess damage and its cause before choosing between a repair, an insert and a replacement part.
- Estimate thermal expansion, restrained stress and weld metal volume, and explain how they drive shrinkage and distortion.
- Plan joint preparation, welding sequence and preheat for a repair, and say what each choice is meant to control.
- Recognise when a repair touches regulated pressure equipment and needs qualified procedures, inspection and approval.
- Assemble a repair dossier that records the damage, decisions, procedure, inspection and return-to-service evidence.
Inside this book
Chapters
- 01Read the damage before choosing a repairEstablish what failed, why it failed and what the part must still do before deciding between a weld repair, an insert and a replacement.
- 02Heat, expansion and shrinkageEstimate thermal expansion and restrained stress, and see why heating part of a plate leaves it shorter and stressed once it cools.
- 03Joint preparation and weld volumeChoose an excavation and groove shape that reaches sound metal, allows full fusion and limits weld volume, and calculate what each choice deposits.
- 04Welding sequence: back-step and balanceUse back-step, skip and balanced sequences to spread shrinkage, and plan the order of welds so each one works against the smallest restraint.
- 05Preheat, hydrogen and coolingDistinguish preheat used to share shrinkage from preheat used to prevent hydrogen cracking, and estimate weldability with a carbon equivalent.
- 06Patches and insertsShape, orient and size a welded insert so its edges sit in sound metal, avoid lines of weakness and keep weld length and restraint under control.
- 07Cracks between holes and in knucklesTreat cracks across ligaments and flange radii as evidence of cyclic strain, and recognise when closing holes changes how a plate is supported.
- 08Building up wasted metalSurvey thinning before deciding on weld build-up, compare deposited metal with an insert, and read published limits as an example of how regulators draw the line.
- 09Procedures, welders and inspectionReplace judgement by eye with qualified procedures, qualified welders, suitable inspection and the approvals regulated equipment requires.
- 10The repair dossierAssemble the damage record, decisions, procedure, sequence, temperatures, inspection and return-to-service statement into one record that others can check.
References and source notes
The manuscript and worked examples are original KEVOS® writing. References inform particular concepts; their authors do not endorse this book. Web references were consulted on 23 October 2026.
- Air Reduction Sales Company, New York. Airco Welding of Locomotive Fireboxes (Booklet Number Four) (1919). Historical primary source used throughout as a case study of early oxyacetylene firebox repair practice. Its procedures are described and discussed, not reproduced, and they are not modern repair instructions.
- United States Federal Railroad Administration. Title 49 Code of Federal Regulations, § 230.33 Welded repairs and alterations (current regulation). Used in Chapter 8 as a published example of how a regulator limits weld build-up of wasted boiler plate. It applies to steam locomotives in the United States, not in Australia.
- TWI. Distortion: types and causes, Job Knowledge 33 (technical knowledge article). Reference for the forms of welding distortion and the factors that control them, discussed in Chapters 2 and 4.
- TWI. Distortion control: prevention by fabrication techniques, Job Knowledge 36 (technical knowledge article). Reference for back-step, skip and balanced welding sequences discussed in Chapter 4.
- TWI. Defects: hydrogen cracks in steels, prevention and best practice, Job Knowledge 46 (technical knowledge article). Reference for the role of preheat, hydrogen control and carbon equivalent in avoiding hydrogen cracking, used in Chapter 5.
- TWI. What is the difference between the various carbon equivalent formulae used in relation to hydrogen cracking? (technical FAQ). Source for the IIW carbon equivalent formula and its limits, used in Chapter 5.
- Standards Australia. AS 1228:2016 Pressure equipment: Boilers (2016). Cited in Chapter 9 because its scope includes guidance on locomotive and other heritage boilers. No content of the standard is reproduced; obtain the current edition before use.
