Thermal power plants (TPPs) operate under intense thermal, mechanical and chemical stresses, which degrade critical systems and components over time. As India continues to rely heavily on coal-based power, particularly amid growing demand and renewable intermittency, the role of structured repair and maintenance becomes increasingly strategic in sustaining plant performance and reliability.
Repairs in TPPs are often necessitated by material fatigue, thermal cycling, corrosion, erosion and operational anomalies. Boiler repairs may involve retubing, header and piping replacements, or welding and cladding of eroded areas. In high-temperature zones, special alloys and coatings are used to enhance durability. Turbine repairs frequently include the replacement of eroded or cracked blades, correction of shaft misalignments and refurbishment of sealing systems to reduce leakage losses and restore thermal efficiency.
Generators, being critical to power output, also undergo substantial repairs. These range from rotor rewinding and stator insulation restoration to bearing replacement and rebalancing. Structural elements such as chimneys, cooling towers and coal handling systems, which are exposed to long-term stress and environmental degradation, are often repaired through concrete reinforcement, anti-corrosion treatments, and realignment of mechanical systems such as conveyors and crushers.
In many cases, auxiliary systems such as air preheaters, feedwater heaters and ash handling equipment also require targeted repairs to prevent cascading failures. The scale and complexity of such tasks often necessitate collaboration with original equipment manufacturers or specialised engineering firms capable of mobilising skilled manpower and heavy equipment swiftly.
Repair activities are primarily executed during scheduled outages or unplanned shutdowns. The ability to diagnose problems quickly, procure spares in time and execute repairs within defined time windows is critical to minimising revenue losses. Additionally, in older plants, retrofitting with upgraded components during repair phases can provide an opportunity to enhance system performance and extend operational life, offering a cost-effective alternative to greenfield investments.
Maintenance strategies
A robust maintenance framework is equally vital for TPPs, not only to preserve plant integrity but also to prevent breakdowns that could lead to extensive repairs or forced outages. Maintenance practices are generally categorised into preventive, corrective and predictive approaches, each playing a distinct yet complementary role.
Preventive maintenance: This involves periodic servicing and inspection of equipment based on predefined schedules or operational hours. It involves cleaning, lubrication, calibration and timely replacement of parts before failure occurs. In boilers, for example, this might entail the regular descaling of tubes, inspection of refractory linings and checking of safety valves.
Corrective maintenance: This process is initiated in response to detected faults or equipment malfunctions. Rapid identification of the root cause is crucial to minimise downtime. Depending on the severity, corrective actions may range from valve and gasket replacements to more complex interventions such as refurbishing heat exchanger bundles or overhauling failed pumps and motors.
Predictive maintenance: This is the most advanced tier, using real-time data and analytical tools to forecast failures before they occur. By analysing parameters like vibration levels, thermal profiles, oil quality and acoustic signals, engineers can detect early signs of deterioration. Tools such as infrared thermography, ultrasonic testing and oil analysis enable timely intervention during planned maintenance windows. While it requires investment in sensors, data analytics platforms and skilled analysts, predictive maintenance reduces unplanned outages, lowers repair costs and extends equipment lifespan.
Utilities are increasingly adopting non-destructive testing methods to evaluate the health of components without dismantling them. Techniques such as radiography, magnetic particle testing and dye penetrant inspection are used to detect surface and subsurface defects, especially in high-pressure components.
Conclusion
Challenges such as financial constraints, shortage of skilled personnel and scheduling maintenance without disrupting grid supply complicate implementation. However, the benefits of a cohesive repair and maintenance programme, such as improved performance, reduced outages, lower lifecycle costs and extended plant life, far outweigh the hurdles. As the energy transition progresses, ensuring the operational readiness of existing thermal assets through disciplined repair and maintenance will remain a cornerstone of India’s energy reliability strategy.
Aastha Sharma