Expert insights

For steam turbines, rotor or last stage blade cracking are among the more common risks with aging units/parts. These can also have the most significant impact on your operation in terms of a forced shutdown or potential safety issues.

Other common age-related issues include:

• Steam valve damage
• Outer casing damage
• Diaphragm creep
• Component brittlement
• Lubricant life
• Auxiliary systems end of life—including coolers

Understanding the operating boundaries of individual components in your steam turbine can help you better anticipate potential issues, as well as plan for emergent work that may be discovered during a planned outage.  

In the HP/IP section, cracking or creep can be caused by cycling in terms of starts/stops or load changes, as well as high temperatures. In the LP section, surface pitting or corrosion in crevices can cause similar cracking or creep issues. 

• Severity of cracks or creeping can be determined by assessing a sample of the rotor or conducting non-destructive testing, which in some cases can be done on site. These analyses can help determine the remaining life of the rotor, and a viable repair solution in many cases. 
• For older un-bored rotors, an ultrasonic inspection can be conducted to pinpoint hard-to-access high-stress areas on the unit 

Yes. First, non-destructive testing can be performed- in some cases on site- to determine if a last-stage blade can continue to be used in operation safely. If not, one option is having a thermal study performed to determine the impact of removing the blade(s) and operating without them. This will result in performance loss, but can be an option to safely resume your operation faster with temporary modifications. There are similar service options for both rotating or stationary blades/buckets.

In the inner casing, material loss can occur over time due to corrosion. To prevent further loss and if the casing is deemed to still be safely operable, a weld repair or erosion protection ring can be installed. 

On the outer casing, cracks or deformation can occur from several factors. On site welding can address such issues in some cases, while others may also require additional machining which is typically performed in a repair shop.

Essential emergency spare parts for steam turbines include bolting hardware and valve internals. While Steam Power maintains a stock of certain components, inventory availability varies. Therefore, anticipating and proactively planning for more commonly known parts issues related to wear and tear or aging helps reduce the incidence of failures, as well as keep outage schedules on track.

Addressing steam joint leaks is crucial due to the potential danger posed to personnel, and it requires a system-level strategy. This includes diagnosing the root cause, making repairs such as bolting upgrades, steam dams, sealants, or half-joint repairs, and potentially machining the joint and boring internal fits to restore flatness and prevent leaks. Quick and reliable repairs are also essential when considering the impact of steam leaks into the atmosphere. 

For generators, rotor/stator winding degradation, along with seal/cooler leakage account for ~80% of aging unit issues. Others include:

• Exciter flash over
• HV bushing failure
• H2 seal wear/leakage
• Cooler leakage
• Auxiliary systems end of life

Understanding the operating boundaries of individual components in your generator can help you better anticipate potential issues as well as plan for emergent work that may be discovered during the course of a planned outage. 

•  A stator bar ground fault can lead to a forced outage from a system protection trip.
• Leakage in the stator can result in hydrogen getting into the water which is a safety risk, or water can seep onto the stator bars.
• Damage to the stator core can also lead to a forced shutdown.

Repair and parts replacement solutions can address these issues, but an effective preventive action to avoid them is using software monitoring and/or inspection services to pinpoint emerging issues before they become serious.

An exciter flash over is triggered by a progressive loss of contact between the rings and brushes. This can be caused by dirt contamination, worn brushes, vibrations or plugged vents. A flash over can burn out certain components which then need to be replaced. The best ways to prevent this from occurring is to replace brush holders when their springs are aging, or to polish/turn slip ring surfaces through machining which can be conducted on site. 

Some common signs include:

• Shorted turns
• Vibration issues
• Excitation current increases to maintain output
• Inability to maintain output due to excitation limitations

The best way to assess the ROI of a rotor life extension is to examine your operating profile within the context of your expected remaining life cycle. If your operation is more cyclical, you may want to do a starts-based calculation to determine how much more time a life extension will deliver to your operation. If you run your site longer periods of time without shutting down, an hours-based approach probably makes the most sense to understand your life extension ROI. Our team can collaborate with you to help calculate the benefits of a rotor life extension based on your specific operating profile. 

Depending on configuration, some units don’t require other component replacements/modifications when replacing or exchanging a generator rotor. If any are needed, they commonly include:

• Oil deflectors
• Bearings
• Hydrogen seals
• Excitation system settings

The degradation of insulation- which can be accelerated by oil contamination- can trigger a winding short. Copper distortion or connection issues can also cause this issue. Aging, along with more cyclical operation can be contributing factors to a winding short.

There are several repair solutions for a winding short including a full or partial rewind either on site or in a repair shop- this can be done with either existing or new copper. The additional benefits of a shop repair include the potential for faster, less costly work scope due to having an established, controlled work environment. 

Cycle time for a winding repair varies depending on the scope required. A pre-planned full field rewind takes, on average, approximately 30 days. However, some repairs can be performed in as little as 1-2 weeks. Rewinds related to forced outages typically take longer when new parts/materials need to be ordered.  

While we believe that maintaining your controls as a holistic system will deliver the best life cycle outcomes, we recognize that operators in later life cycle stages need to limit their maintenance costs. 

With the ability to deliver individual components (including HMIs, controllers, cards and CPUs), we can help limit the scope of service work, which may result in lower project costs. By designing our parts with the compatibility for this ‘a-la-carte’ type of maintenance, our team can help ensure that your controls system has obsolescence protection with cost-effective services. For fleet-level operators, we can collaborate on end-to-end controls packages - featuring our most advanced technologies - to support your plant systems holistically and efficiently. 

We continue investing in a holistic platform of resources to help you optimize your controls systems throughout their life cycles. They include:

• Notification & delivery of software updates
• Preventive maintenance recommendations
• Cyber security assessments
• Cyber security updates/alerts
• Option for a controls ‘resident engineer’ on site
• Technical information letter (TIL) program
• Parts program
• Training
• 24/7 technical support 

We’re also developing a dashboard that will provide visibility to your hardware and software life cycles, as well as your software vulnerability status. To help you plan for maintenance actions, this portal will also provide recommended software updates, both from obsolescence and vulnerability perspectives. 

We recommend that your steam plant’s control system be assessed every year by either our service team or yours. This includes performing a system backup and restore, in addition to addressing any issues that may be seen. Our team can perform this scope during the course of a planned (or unplanned) outage for more efficient maintenance. In fact, some of our field engineers that service steam turbine and generator equipment can also service your controls during the same visit to your site.   

As with most technologies, taking a preventive approach to servicing your controls system will likely result in the most efficient life cycle costs and performance. Some key preventive actions include: 

• Integrating your overall maintenance strategy into your outage cycle planning
• Identifying actions to address recent system alarms 
• Testing for potential power supply failures or ground faults
• Taking a site-specific approach to cyber security with recommended patches and updates
• Assessing spares and obsolescence options  
• Informal training/coaching as needed based on your evolving workforce 

An effective independent maintenance program should start with reviewing our GEH-6721 volume 2 guide, which provides instructions on Mark* VIe maintenance including panel cleaning, cooling fans check, maintaining temperature, terminal tightening, air filters cleaning, review of diagnostics logs and execution of corrective actions. 

You can also do an obsolescence evaluation to understand your future parts needs. In addition, review all applicable Technical Information Letters (TILs) that we’ve posted and implement them as recommended. Of course, our service team can assist with these activities as needed. 

Absolutely. We have several resources that can support your spare parts strategies. The first step is to understand which control systems you have, and where they are in their life cycle. Our parts experts can help by performing a spare parts assessment of your existing spares to help ensure they are the latest revision, and are still applicable for your controls system. Recommendations can then be made for critical spare parts and recommended actions for your existing spare parts. 

We’ve designed our newer controls systems to be compatible with many components designed for previous versions to help limit your life cycle costs, and offer more maintenance flexibility. There are some limitations on new parts availability with certain systems such as Mark* V controls, however, we do have limited refurbished parts available, as well as options for repairs and replacement exchanges. 

Yes. Our service team continues to support both OEM and legacy brand controls systems including the Mark* VIe and ALSPA systems. Our portfolio for both platforms includes core services and life extension solutions, along with current cyber security technologies to help protect your plant’s ecosystem. 

The Mark* V system is not produced anymore, so new parts are not available. We do have limited refurbished parts available, as well as options for repairs and replacement exchange. We also have OEM factory-trained field engineering resources for your service needs. In addition to ongoing support, an existing Mark* V can be replaced in full with a new Mark* VIe control. A Mark* VIe control offers many advantages over the legacy Mark* V control, including a distributed control architecture, reduced footprint, enhanced computing, and simpler product structure. 

Yes, our team provides in-person and remote training on our controls systems. In addition, using our virtual controller software, you can have a safe environment at your site for testing and training on control system activities. 

If you’re interested in having a Steam Power consultant help your team maintain your controls system, we can provide you with a dedicated expert to help with activities including: 

• Pre-outage assessments
• Spares and obsolescence assessments 
• Preventive maintenance assessments 
• Operational productivity assessments 
• Cyber security assessments
  

We can partner with you to provide OT-specific cybersecurity assessments based on the Center for Internet Security (CIS) Top 18 Security Controls, with multiple levels to meet your unique needs. Implementing just the first five of these controls can reduce your risk of cyber attack by up to 85%.

Additionally, patching your systems is essential to protect your assets. Our patch validation program provides monthly operating system and application patches, as well as antivirus and intrusion-detection signature updates for human-machine interfaces (HMIs), servers, switches, and network intrusion-detection devices. Monthly updates can be applied to individual HMIs or via the SecurityST appliance for network-wide deployment.

And, our team posts security updates—for all of our controls platforms—on our public website as they become available to help you stay informed on current events in cybersecurity. As part of your ongoing efforts, we recommend that you do a cybersecurity assessment once a year to help ensure your systems and site are protected against cyber threats

If a network intrusion detection system is installed or to be installed, we recommend that you look for syslog/SIEM messages to understand if there are any cyber attacks being attempted. In addition, vulnerabilities related to Windows OS, tool boxST, QNX OS, CISCO NW switch IOS, and fortigate OS, are updated in our cybersecurity portal. These notifications also include recommendations for software updates, so we recommend you keep an eye out for them, and install software updates/patches as soon as you can once they’re available. 

Controls isolation is becoming less viable as a cybersecurity strategy, in part because there are other mechanisms used by infrastructure managers and adversaries alike to perform the necessary task of moving data into and out of islanded control system networks. These include the use of USB sticks and removable media to bring patches and updates into the control system environment, and to move business data regarding production out to an otherwise unreachable business network. These mechanisms can carry viruses and malware without the knowledge of plant maintenance personnel. 

Unfortunately, one of the largest threats comes from inside the power plant, like a disgruntled employee or someone unintentionally connecting a phone or USB port with a virus. 

Beyond the risks associated with removable media, there are other potential issues with unexpected connectivity enabled by an adversary, malicious insider, or even an insider acting in good faith but incautiously. Even if wireless networks are forbidden, one of these kinds of actors can easily add wireless access points to the network by plugging it into an unused and unblocked network port. Such wireless access may even be accessible from outside the plant perimeter.