Turbine technology |Operating experience Steam turbine failure trends An insurer’s perspective Tom Hadfield Senior Engineering Specialist, FM
Steam turbines are critical components in power generation and various industrial processes, but despite advancements in design, materials and maintenance practices, steam turbine failures continue to occur. Often these failures result in substantial unplanned downtime, equipment damage, loss of generation and business impact. Steam turbines are designed to operate within specific parameters. These include temperature, pressure, steam quality/purity, vibration, and operating profiles. Deviating from the design parameters can increase stresses, accelerate component degradation and be a precursor to mechanical failure mechanisms.
This article examines failure trends FM has seen, focusing on the three most common root causes. It also outlines practical strategies for risk mitigation, aiming to enhance reliability, extend equipment life, and reduce operational disruptions.
What are some of the key loss drivers for steam turbines?
Flow path component damage Flow path component damage remains one of the leading causes of steam turbine failures. These failures are often attributed to domestic object damage (DOD), originating from internal component failures, and foreign object damage (FOD), caused by external debris entering the turbine.
While the initial failure may be localised, damage to downstream components can be extensive, often resulting in prolonged outages and costly repairs.
Contributing factors include, thermal/cyclic fatigue, high/low cycle fatigue, creep, impact damage, corrosion, erosion and inadequate foreign material exclusion programmes.
Many steam turbines operate within a challenging energy market. As a result, they are experiencing faster ramp-up rates, low load operation and two shifting. This is elevating stresses experienced by critical components and contributing to some of the factors listed above. Two shifting is required to meet electricity peak demand. This mode of operation significantly impacts operational integrity by accelerating component degradation. This can lead to increasing thermal stresses and fatigue, resulting in premature mechanical failure and contributing to domestic object damage.
Low load operation is required when demand is low. This supports grid stability and allows rapid load increases. However, running at low load can lead to inefficiencies, increased heat rate, and heightened susceptibility to fatigue. These conditions can degrade performance and reduce the turbine’s operational lifespan.
Who is FM?
FM is a commercial property insurer specialising in multiple industries, including power generation. The company is a leader in risk management, insuring many of the world’s largest organisations – including one in four Fortune 500 companies. FM believes that the majority of losses are preventable. Its mission is to reduce their frequency and impact by analysing large loss events and sharing these insights with the industry. FM insures over 4000 steam turbines globally and has investigated hundreds of steam turbine losses. Specialist teams review this data to identify key loss drivers and propose effective
strategies to mitigate future risks. With deep experience and extensive data from decades of protecting steam turbines, FM says it sees resilience in ways that others can’t.
Maintaining precise water chemistry and steam purity is essential. Inadequate water treatment or contamination can result in corrosion, scaling, and deposits, all of which impair turbine efficiency and reliability. Corrosion can also contribute to component failure and subsequent domestic object damage. In particular, it can lead to pitting and evolve into stress corrosion cracking (SCC). This is a severe failure mode that occurs under tensile stress in corrosive environments. The last- stage blades are highly susceptible due to their exposure to wet steam and high tensile loads. Some measures to mitigate flow path component damage include:
Implementation and enforcement of a robust Foreign Material Exclusion (FME)
14 | July/August 2025|
www.modernpowersystems.com
Source of images: FM
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