Preparing for the unexpected: A guide to steam turbine outage planning

Planning a steam turbine outage comes with unique challenges, as no two turbines are exactly alike in operation or configuration. Even turbines within the same plant can differ significantly due to years of operational factors and past maintenance decisions. 

In this blog, we’ll share insights on best practices for outage planning, covering key challenges, strategies, and emerging trends to help navigate these complexities effectively. 

The growing challenge of steam turbine outages

Each year, approximately 200 outages occur across the steam turbine fleet, with nearly 50% of them unplanned. These unplanned outages often result in costly downtime and extended repair schedules. On average, unplanned outages lead to an additional 3.5 days of downtime, costing around $150,000 in lost generation and increased repair expenses. 

Several industry trends are making outage planning more complex: 

• Aging assets: Many combined cycle steam turbines are 20+ years old, reaching their second and third major service intervals.
• Extreme weather events: Unpredictable weather patterns lead to longer and more intense outage peaks, reducing outage windows.
• Increased cycling: Plants that were once base-loaded are now required to start multiple times per day, accelerating wear and tear.
• Workforce changes: As experienced engineers and technicians retire, industry knowledge gaps are emerging.
• Supply chain dynamics: Lead times remain uncertain and haven't returned to pre-COVID levels.

Key failure points and how to plan for them

Effective outage planning starts with understanding common failure points and ensuring contingencies are in place. Some of the most frequent issues include: 

1. Diaphragm and blade wear

• Over time, some diaphragms may experience dishing and erosion, requiring major repairs or replacements.
• Inlet stage diaphragms face the most wear due to exposure to high-temperature steam.
• Planning for long lead-time parts is crucial to avoid unexpected delays. 

2. Valve and casing failures

• Many steam turbine valve casings and bolted joints develop cracks over time.
• Conducting proper pre-outage inspections and ensuring availability of replacement bolts and sealants—as well as the equipment required to replace them—can prevent schedule overruns. 

3. Rotor and steam path damage

• Foreign object debris (FOD), water induction, and thermal stresses can cause rotor and blade failures.
• Pre-outage borescope inspections and stocking critical spare parts can mitigate risks. 

4. Supply chain delays

• Post-pandemic supply chain disruptions have extended lead times for essential parts.
• Partnering with Original Equipment Manufacturers (OEMs) like GE Vernova for early procurement and shared inventory strategies can help mitigate delays.