In May, GE’s Power Services business unveiled its ‘Cross-Fleet’ gas turbine solutions portfolio. With a GE a fleet of about 7500 gas turbines, and associated balance-of-plant, the company says the central goal of Cross-Fleet is to expand the installed base in which it installs its technology.
Explaining the thinking behind Cross Fleet in Baden, Switzerland, during the official introduction of the offering, Scott Strazik, President and CEO of GE’s Power Services business, said: “Cross-Fleet is not [just] about servicing other OEM machines; it’s about taking those machines and making them our own – adopting those machines and inserting our technology.”
The first two other OEM turbine models being addressed are Siemens’ SGT-800 and 501F units manufactured by Siemens and Mitsubishi. GE estimates there are 300 501F units operating worldwide, mostly in the Americas and Asia and believes it can bring significant value to the table in terms of heat rate. The SGT-800 – until now solely serviced by Siemens – also represents a market of about 300 units, predominantly in Europe, Russia and more recently, Thailand.
By taking proven GE gas turbine solutions and applying it to a wide variety of engines, GE says it is able to: improve asset performance, i.e. better efficiency and output, to provide more value for the customer; reduce operating costs; integrate the balance-of-plant to deliver plant-level improvements; and improve gas turbine reliability and availability.
“We think we can do some things to help with cost or operating expense,” Jim Masso, Cross-Fleet Engineering Leader, told GTW: “For example, the SGT-800 is one of the more expensive gas turbines per MWh to run. Here we can apply lower cost alloys – use our large supplier network to provide materials and alloys that allow them to run at a lower cost.
He added: “Offering plant level improvement is also an important aspect. One of the big concerns when a gas turbine is upgraded is how it works with the rest of the plant. So we have a large plant team and digital team to look at the impacts and make sure it works with the rest of the plant.”
With regards to reliability and availability, he said: “We’re extending intervals between outages, which means fewer outages. And we’re focusing on what we can do for the entire plant in order to improve reliability. Although intervals depend on the gas turbine, generally speaking, we are able to improve intervals by about 20-30 per cent on hot gas path components.”
In order to deliver its offering and accelerate time to market, GE has acquired a number of spare engines, engine components, and design IP for a variety of turbines including the 4000F, SGT-800, and 501F
“To have credibility in this space, it’s absolutely necessary to have spare engine parts. And more importantly, we’ve gone out and ‘characterized’ a number of different engines, so that we also have our own hardware that we can develop and apply to these gas turbines,” explained Masso.
“First and foremost, we’re making our own [parts]. But for the initial parts, in many cases we’ve bought assets that are being under-utilised. We’ve purchased whole engines from plants that don’t have a lot of run-time. In one case, we bought a whole power plant.”
GE stresses that Cross-Fleet is “very much a global capability”, having reserved casting slots and repair capacity at various locations. Already it has performed outages on Siemens and MHI machines in several countries, including Oman, Netherlands, Germany, Mexico and the USA. According to GE, this is its third year of significant investment during which it has been testing, dialoguing, signing and executing orders. Already the company says it has a more than $200 million backlog in orders and has completed over 15 outages.
Outages have covered a number of different scopes. “There’s been everything from small borescope inspections and combustion inspections, through to majors and implementation of customisation and upgrades to introduce GE technology into the engines,” said Paul Wise, Operations Leader for Cross-Fleet.
“We’ve been looking at what we can already use from the existing GE and Alstom service platforms. And then developing the repairs technology, extending our field service tooling field service execution capability and bringing in people that have experience on these frames,” he added.
GE says that over the last 18 months or so, it has been building its infrastructure and capabilities in supply chain and operations to complement its existing service team around the world.
It has dedicated engineers working on non-GE gas turbine technology, and has access to more than 1500 gas turbine engineers. A full field service team is in place and there is a global engineering support network with remote monitoring and diagnostic capabilities. Dedicated teams are also in place to perform upgrades and retrofits on control systems, including the T2000, T3000, Netmation and PCS7.
Masso added: “There’s a bit of an obstacle in our industry, where all the big OEMs have gone for these highly complicated single crystal castings, which are fairly expensive. And there really is a shortage of capability in the industry to support some of these hot gas path or turbine section developments. So one of the things we did was work with a number of vendors to build-out our strategy to produce some of the more high capital, specialised hot gas path components. Having the ability to produce parts that are more widely available and more reasonable in terms of cost is absolutely integral to our strategy.”
GE says this will see more components made from directionally solidified materials used in place of more expensive single crystal materials. Many of these components have been tested at GE test facilities in Switzerland and in the US.
“The 501F/701F burner validation test has been carried out in Birr, Switzerland, and in Greenville, USA,” said Masso. “We involve our customers as well. We try to make sure they witness the testing, which is really valuable for us as well, as it allows us to fine-tune what we are doing to the engines.”
Before selling any products or services, GE completes what it calls a detailed engine characterization. This involves gaining power plant understanding to learn how the gas turbine interfaces with the surrounding equipment, as well as understanding the tooling that is available to perform outages on site. This has been done at a number of locations.
This, says GE, allows it to capture a tremendous amount data from the engine. Explaining the process, Wise said: “These are typically not sites where we have installed or commissioned the larger assets. So our depth of knowledge and the need to learn about the interfaces between the gas turbine, the power train and the rest of the plant, etc., has become part of our standard engagement with customers prior to any sort of execution.”
According to GE, it is a very rapid process. “We bring it into the detailed design process and after we’ve completed this characterization it pretty much follows how we develop hardware for any other engine. There is conservatism in our approach in that we only apply proven GE technology on mature F-class technology,” said Masso. “And it’s not just about characterizing the engine; it’s about characterizing the fleet as a whole. We’ve spent lots of time gathering operational data and have gone out to sites and added additional instrumentation to better understand some of the operating conditions of the engines.”
Giving an example of the speed with which the whole process can be done, Masso referenced a project featuring an SGT-800, executed in Dammam, Saudi Arabia. GE bought the entire power plant in January 2017, starting the characterization process. By May that year, it had disassembled and re-assembled the engine multiple times, scanning every component within the engine – all hot gas path parts, compressor parts, rotor, bolting and even small items such as consumables, seals, etc. By June, Masso said hardware was available for testing. “We used rapid prototyping and 3D printing, or additive manufacturing, to produce some of our initial hardware for this engine and by October, we were completing full-scale combustion testing on some of this hardware.”
The process basically involves taking apart the engine and measuring every single component in the engine, prior to building an engine performance model to understand how the engine runs.
“We use a wide variety of techniques such as X-ray and even destructive testing. We will measure internal cooling features and test various alloys,’ said Masso. “But we get engines in a variety of different states so we can understand how they age. We bring this all back so we can build our own baseline model of the engine.”
These measurements are mapped to operating data from the field, then rapid development techniques are used to produce parts and test hardware. It is a process, which GE says it can “cut and paste to any number of engine technologies”.
After characterization, the research and development process is the same as for any of GE’s other new product introductions. “It’s the same kind of validation testing and same engineering organisation,” said Masso. “We’re using the same teams that develop our most advanced gas turbine components.”
“The Dammam project worked out very well; we have a capable service centre there but we also have these capabilities in Birr, Greenville, and in Poland,” said Masso.
Field service readiness
GE notes, however, that it is not just about understanding the gas turbine for upgrading; validating field procedures – ensuring there is a trained crew and trying out tooling – are also important.
GE has been making some notable advances in its field procedures. For example, removing the compressor rotor on an SGT-800 requires placing the machine in the vertical position, which requires a fairly complicated lift. This usually calls for the machine to be sent to a workshop. While developing its own procedures, GE’s team challenged this concept to see whether it was possible to take the unit out horizontally.
Wise said: “We looked at and came up with some complex tooling designs that allowed the right supports and features of the engine to be protected and came up with a procedure that allowed the rotor of the SGT-800 to be removed horizontally. With the right machine and tooling equipment, this is something that can be done onsite, thus avoiding the need to send it back to a workshop.”
The technique, which GE says has never been performed before, not even by Siemens, has a significant impact for the customer in terms of reduced outage duration and associated cost. The technique has yet to be performed at a client site but has been successfully undertaken multiple times on GE’s own engine, according to Wise, and has since been patented by GE.
GE has also begun building its own portable machine shops on site when performing outages. In many cases it is able to develop tooling on site in parallel with the outage. According to GE, this offers a lot of flexibility.
“There was one outage in particular, which we completed in the US, where we saw a lot of damage to the compressor section. We had to create special lifting equipment for parts of the compressor in parallel to the outage, so there was no impact on the outage schedule whatsoever,” said Masso.
Wise believes this is part of what makes Cross-Fleet and GE unique in this area. “When people look to move away from the OEM, the independent service providers do a good job in terms of service offerings but they don’t have the breadth and the depth of an OEM to provide all of this additional value and investment… this helps differentiate us from others in the market that can simply offer services on these engines.”
GE also argues that the historical development of the SGT-800 gives it an added advantage. During the press meeting in Birr to mark the unveiling of Cross-Fleet, Martin O’Neill, General Manager of the Cross-Fleet and Aero service businesses explained that GE has some “heritage” on the SGT-800 through its acquisition of Alstom. He noted that a lot of the development work around combustion and hot gas path was actually performed in Baden before Alstom sold its industrial gas turbine business to Siemens in 2003. This, he believes, puts GE in a much better position when it comes to implementing improvements that can benefit customers.
Looking at the 501F, GE again has gained knowledge and experience as a result of historical acquisitions. Mitsubishi had a technology collaboration with Westinghouse Power Generation before Siemens bought the Westinghouse division in 1998. At this point there was a technology split on the F-class units, resulting in the Mitsubishi M501F and the Siemens W501F, later renamed SGT6- 5000F.
O’Neill therefore pointed out: “Whether it’s a Mitsubishi or Siemens machine, in whatever region of the world, we have a Cross-Fleet solution for that configuration.”
Component repair is a key part of Cross- Fleet. According to GE, it relied heavily on repaired components in some of the early outages it executed in 2016/early 2017. When repairing components, a central goal is to get more out of them, even compared to when they were new, i.e. putting parts back in as upgraded components.
During one outage, rather than recoating blade 1 of a 501FD3 with a traditional porous thermal barrier coating (TBC), a dense vertically cracked coating was used instead. This can be applied much more thickly to the blade. “In this case it was applied about four times the thickness of the original coating,” noted Masso. This was combined with modifications to the cooling, where GE machined- in cooling paths in the blade.
“This part was originally capable of about 25 000 operating hours. Putting on the better coating, modifying the cooling path and changing some cooling and sealing features allows us to run for about 32 000 hours with some minor performance improvements,” said Masso.
Similar repairs are possible for other combustion hardware. Masso referenced a 501F transition piece that was modified so it could handle longer operating hours through the addition of new wear coatings and TBC.
In another example, ‘Lifesight’ sensors were installed on a 501FD3 blade. This enables the creep state to be measured. “For some of the later stages [of blades] that can’t benefit from coating, we’ll install things that help us measure creep; how the parts age,” said Masso. These repaired and upgraded parts have, according to GE, “been fully successful”. Masso noted: “Our initial entry into the market over a year ago was really focused on repair. Now our own parts are going into machines – we have components available for SGT-800, 501Fs and a few other engines.”
The company says it has recently completed upgrading a Mitsubishi 501F to take it “far beyond where anyone in the industry has taken it” and “far exceed expectations” for heat rate guarantees and performance.
For an operator or customer/user of an SGT-800 specifically, which is very strong in the cogeneration and industrial space, increased performance output can mean additional monetisation if they can sell the additional base load power. It can also mean additional process heat and steam.
On the SGT-800, GE says its upgrades can provide up to about a 6% improvement in power output and up to 1.5% increase in efficiency, depending on the platform – the SGT-800 essentially has three platforms, or evolutions: A, B and C. Platform A was introduced in the late 1980s/early 90s; Platform B in the mid-2000s and Platform C being the current version. In terms of operability, the Cross-Fleet upgrade can improve flexibility by allowing turndown to 40 per cent of full load, while staying within NOx emissions limits.
Notably, GE claims the introduction of its technologies to the machine will allow the time between overhauls to be increased from the OEM’s published 24 000 hours effective operating hours (EOH) to up to 40 000 EOH.
“The interval is largely limited by the hot gas path,” explained Masso. “There have been some challenges with the stage 1 blade. There have been a couple of areas where it will crack. We’ve redeveloped our own version of that blade, as well as replaced a lot of the hot gas path components that were single crystal casting, with directionally solidified castings as well as lower cost Equiax castings. Those upgrades combined with some modifications to the combustion system, improve the capability and nearly double the interval of a 25 000 hour engine. For some of the first hardware we put in, we expect to get about 40 000 hour intervals – without any maintenance to the hot gas path or the combustion system. That’s a pretty big shift for that engine.”
Such maintenance upgrades, he adds, are also about managing and understanding the life of other components. The first F-technology and SGT-800 turbines entered the market in the 1980s and 1990s, they were expected to run in base load but as the markets changed so have their operating regimes. In the case of larger F-class machines, there has been significant investment in optimising their value in markets where there is much more cycling and stop-start operation, and thus reduced running hours. Value can be increased by extending the life of rotors and compressor blades, and by looking at the rest of the plant as it ages, in order to keep it competitive.
But while extended maintenance intervals and reliability are crucial for industrial applications, there are other markets, such as in Southeast Asia, where output is more valuable.
“Our initial entry to the market was focused on maintenance intervals but we are finding that we can now do more things with output. We believe we can upgrade a 10-year old engine to be as capable as a brand new A and B platform SGT-800s in terms of output, while still offering that increased interval,” said Masso.
On the 501F, GE says Cross Fleet can also extend outage intervals but also notes that performance improvements can be more pronounced than on the SGT-800. It claims it can achieve up to an 8 % improvement on performance and up to a 2.5 % improvement on heat rate.
Having completed over 15 outages, covering a variety of scopes, for multiple technologies in seven countries all over the world, GE is confident of its future prospects, including extending Cross- Fleet capabilities to other machines.
Summing up the future near-term potential, O’Neill concluded: “The order backlog is a promising start and I’m glad we have penetrated on both platforms but I would like this business to go at least 2x in the next 12 months.”