The MCBO Blog

Industrial steam boilers stand as the backbone of numerous industrial processes, facilitating the generation of power and heat essential for various applications. These boilers are subjected to relentless demands and are machines built to be robust, enduring the rigours of daily operation. Yet at the heart of these behemoths are components that, whilst intricate in design, must operate without fault within the most extreme conditions: the boiler tubes.

What are Tube Boilers?

Steam boilers can be identified in two categories: water tube and fire tube boilers. In both cases, boiler tubes serve as conduits for the transfer of heat between the combustion gases and the water/steam contained within the boiler system.

In water tube boilers, the boiler tubes are arranged in a manner that allows water to flow through them. These tubes are typically arranged in a grid-like pattern within the boiler's combustion chamber. The combustion gases generated by the burner pass around the outside of these tubes, heating them to high temperatures. As the hot gases flow past the tubes, heat is transferred through the tube walls to the water circulating within them. This heat exchange process causes the water to absorb heat energy and eventually reach boiling point, producing steam. The steam generated in the water tubes is then collected in the steam drum for further distribution throughout the system.

In contrast, fire tube boilers feature tubes that are immersed in the water within the boiler shell. These tubes run through the length of the boiler, connected to the combustion chamber and smokebox tubeplates. Fuel is burned within the furnace/combustion chamber, generating hot gases that flow through the space surrounding the boiler tubes. As the hot gases pass through the tube bundle, heat is transferred from the gases to the water surrounding the tubes. This process heats the water, causing it to boil and produce steam. The steam generated in the fire tubes rises to the top of the boiler shell and is collected in the steam space for distribution. Having been used almost exclusively in steam locomotives from their inception, fire tube boilers were and remain the prevalent industrial boiler type in the UK.

In both cases, boiler tubes endure a relentless barrage of extreme conditions, ranging from scorching temperatures and pressure differentials to corrosive substances. Despite their resilience, the cumulative effects of prolonged exposure manifest in various forms of degradation. Because boiler tubes have to endure extreme variations of temperature and pressure, they are prone to scale build-up and cracking over long periods.

Neglecting the signs of tube deterioration brings about dire consequences, spanning from compromised performance to catastrophic failures. As the structural integrity of these tubes deteriorates, imminent threats to employee safety and operational efficiency emerge. The inefficiencies resulting from compromised tubes translate into exorbitant operational costs and environmental repercussions.

 A Comprehensive Approach to Retubing

Retubing requires a procedural approach with meticulous assessment, precise execution and quality assurance. McEwen's boiler repair teams are highly skilled in undertaking tube repairs and replacements, often working around the clock to ensure the boiler is not out of action for a long period.  All our engineers hold the relevant certifications required, such as confined space entry and coded welding qualifications.


Qualified inspectors conduct visual inspections and Non-Destructive Testing (NDT) to identify areas of boiler tube pitting and cracking. This detailed examination aims to determine the extent of degradation and its underlying causes.

Extraction & Repair

Damaged boiler tubes are removed from their housing for replacement or repair. If a tube end has repairable faults that can be safely restored to full operation, approved repair methods are utilised.

Replace & Install

New boiler tubes are purchased and then prepared in our workshop according to specifications and standards. Tubeplates, which connect the tubes between the combustion chamber and smokebox, are cleaned, and repaired in readiness for the fitting of the new tubes. The new smoke tubes are then installed into the boiler and are power expanded. They along with stay tubes are seal welded by our in-house coded welders.

Testing & Accreditation

Certified inspectors oversee the repair process, conducting several staged inspections and tests from both a visual and NDT standpoint. These tests culminate with a final hydrostatic test, normally to 1 ½ times the design pressure of the boiler or vessel.

We supply all the relevant documentation in advance of the repair commencing, which includes Risk and Method Statements, Material Certification Certificates and Weld Procedures.


The Long-Term Benefits of Retubing

Retubing offers benefits beyond the immediate need for repair. By revitalising the boiler’s core components, retubing enhances operational reliability, safety, and efficiency. The key benefits of retubing include:

  • Improved Performance: Retubing restores the boiler to its optimal operating condition, ensuring consistent and reliable performance over time. By replacing worn or damaged tubes, heat transfer efficiency is maximised, leading to better steam generation and energy utilisation.
  • Enhanced Safety: Worn or damaged tubes pose serious safety risks, including leaks, ruptures, and potential boiler failures. Retubing eliminates these risks by replacing compromised tubes with new, structurally sound ones, ensuring a safer working environment for personnel and equipment.
  • Energy Efficiency: Optimal heat transfer achieved through retubing enhances energy efficiency, reducing fuel consumption and operating costs. Improved efficiency also contributes to environmental sustainability by lowering emissions and resource usage.
  • Regulatory Compliance: Retubing ensures that the boiler meets or exceeds regulatory standards and safety requirements. Compliance with industry regulations not only avoids penalties but also demonstrates a commitment to maintaining high safety and environmental standards.
  • Cost Savings: While retubing involves upfront investment, the long-term cost savings outweigh the initial expenses. Reduced energy consumption, minimized downtime, and extended equipment lifespan contribute to significant cost savings over the boiler's lifecycle.

Our retubing services are at the heart of our industrial boiler repair solutions because they are fundamental to a boiler’s performance, efficiency and longevity. Our years of experience in repairing and rebuilding firetube and watertube boilers guarantee that your retubing project will return you to full operation with improved efficiency, reliability and safety within as short a time as possible.