EASY READ | 3 - 4 min
Having been in the business for 35 years, I’ve talked to many customers all over the country and have seen a lot of different issues that can affect a steam generator’s performance. Some of these problems are known and obvious, but others are harder to detect.
One good example is the installed base of Chinese OEM generators. Customers running this fleet of generators are experiencing performance issues that are caused by premature aging: Fixes that they might expect to do when the unit is at midlife, or around 25 years, are becoming necessary as early as 5-10 years. Left uncorrected, these issues can cause equipment damage and unplanned unit shutdowns.
Fortunately for these customers, GE’s engineers and field employees have extensive experience across OEM and other OEM fleets, and a suite of unique repairs to restore your generator’s integrity and postpone more extensive life extension solutions. This team has been able to correct multiple issues with our customers’ Chinese OEM generators. Let’s focus on stator and rotor issues.
Stator bar failures
In Chinese-manufactured air-cooled generators, I have noticed several early stator bar failures especially in the GVPI (Global Vacuum Process Impregnated) insulation technology machines. After careful analysis, my team and I have traced these failures back to a high level of slot partial discharges that were coming from deficiencies in the insulation manufacturing process.
In addition, we have seen stator bar blockages and high bar temperatures in Chinese-manufactured water-cooled generators using low oxygen water technology. These faults occur when copper oxides build up and start reducing the generator’s cooling efficiency, which can lead to stator bar overheating, load reduction and unscheduled maintenance. Left unchecked, you could be looking at a shorter component lifetime, equipment damage and an unplanned unit shut down.
For customers experiencing these types of stator bar issues, we have been able to provide several different customized solutions-including generator health monitoring (GHM), where online parameters are analyzed continuously to predict failures. I have used End Winding Vibration (EWV) data from GHM to prevent failures by positive interventions like slot re wedging & overhang consolidation to reduce winding vibration.
Our CUPROPLEX TM chemical cleaning technology protects your stator bar’s integrity and has an advantage over mechanical cleaning as it can be applied while the unit is online—which means you won’t lose time or money due to an outage.
With teams and spare parts close to our customers, we can also provide any needed parts to customers on short notice and with the confidence of our GE quality assurance programs.
We have also seen that Chinese-manufactured generator rotors are prone to loosened overhang blockers, which are caused when intense mechanical and electro-magnetic forces can cause premature aging of the end winding structures. The resulting loosening and deterioration can cause the blockers to break and require removal and repair, which our GE teams can address with improved parts and high-quality services.
Another thing to watch out for is thermal sensitivity, which can cause rotor vibrations to reach very high rates because of increased loading. As the preferred provider for most rotor solutions, GE can work with customers to address this issue with onsite solutions or balancing and tunnel solutions performed in our workshop.
Get in touch!
If you have a Chinese OEM generator, you’re probably experiencing one or more of these stator winding issues—or you could soon. Get in touch, and let’s work together!
Author: Sushil Trivedi
Title: GE Steam Power, India
Located in Ahmedabad, Gujarat, Sushil has 35 years of experience in the manufacturing and servicing of large turbo generators and expertise in both onsite generator repair and workshop rotor repair. He has an Electrical Engineering degree (with honors) from IIT–BHU and worked for BHEL for 21 years before joining GE in 2006.