Protecting the world’s largest gas turbine

Our products are used to monitor and protect the largest machines and operations on the planet. That’s not hyperbole – that’s fact. In this series of articles, we examine three of the “world’s largest” and what we do to make them safe and reliable. Here, we showcase the world’s largest gas turbine – the Siemens SGT5-9000HL.


The truth is that large machines aren’t necessarily monitored differently or with different equipment. They may have more measurement points. They may have more complex voting logic. And they may qualify for the most extensive complement of protection and condition monitoring measurements because so much is on the line in terms of lost production when they fail. But it’s basically a matter of more – not different. The consequences of a missed alarm or false alarm is what sets these machines apart. Big means expensive and highly consequential. In this 3-part series we examine big machines and big plants. And not just big – the world’s biggest in terms of power output.

We kick off our series now with an installment covering the gas turbine – the world’s go-to machines for air travel and boasting the highest thermal efficiencies (> 60%) for power generation when in combined cycle operation with a steam turbine.

Humble Beginnings

Although the first true gas turbine was patented in 1791 by John Barber of Nottinghamshire, England, it would be more than 100 years before a gas turbine able to produce more power than it consumed could be demonstrated, and nearly 150 years before one would be put to practical use in power generation service.

Figure 1. Sketch of Barber’s invention from his 1791 patent.

While Barber patented1 his invention, there is no record he ever actually built2,3 the device he sketched in his patent (Figure 1). Indeed, had he built it, he would have quickly discovered that the design suffered from a fatal flaw: thermodynamically, there was no way for it to generate more power than was consumed in its compressors, and thus it was a net consumer of energy rather than producer. Regardless, the fundamental ideas of compressing, burning, and then expanding a flammable gas across turbine blades would eventually be made practical by a later generation of engineers. One of those engineers was Aurel Stodola who was heavily involved in the world’s first gas turbine used for power generation (Figure 2) – a 4MW machine that entered service in 1939 at a municipal power station in Neuchâtel, Switzerland and would provide reliable standby (emergency and peaking) power for the next 63 years. So significant is this machine that it was designated as an international historic engineering landmark by the American Society of Mechanical Engineers (ASME).4,5

Figure 2. Excerpt from article by Aurel Stodola on world’s first gas turbine in power generation service.

The article is referenced in the Jan 20, 1940 issue of Nature (a British scientific journal) and shows the machine on its test bed at the former Brown, Boveri, and Co. in Baden, Switzerland where it was manufactured. You can read more about this machine and the history of gas turbines in our informative whitepaper on gas turbine monitoring.

Steady Progress

From that historic machine in 1939, power output and efficiency would grow steadily over the next 80 years and technology would progress along two separate but intersecting paths: those designed for aircraft propulsion and those for industrial uses. Firing temperatures (Table 1) in the most advanced industrial machines would eventually become so high that exotic alloys would be required for the blading, grown from a single crystal and known as SX (single crystal) technology.

SX technology was pioneered in the 1970s by Pratt & Whitney for its aircraft engines6 such as those used the F-15 and F-16 fighters and later in the Boeing 767 and Airbus A310. Its first use in industrial gas turbines was in the Siemens V84.3 in 1995, 6,7. Today, the technology is routinely employed in G-, H-, and J-class machines from all manufacturers. Efficiency for this class of machines in simple-cycle operation exceeds 40%; in combined-cycle operation it climbs above 60%.


The power-to-weight ratio is of substantial importance for aircraft engines, but of lesser concern in industrial turbines. Regardless, as the power output from gas turbines increased, their size did not increase proportionately. Today’s largest aviation engines produce 100 times as much thrust as the earliest engines yet weigh only 25 times as much – a 400% improvement in power-to-weight ratio.

“…the Siemens giant has a footprint that is approximately the same as the Neuchâtel machine yet produces 150 times as much power.”

On the industrial side, we have already discussed the 4MW unit of 1939. It featured a simple-cycle efficiency of 17.4%, a turbine inlet temperature of 550 C, and ran at 3000 rpm. 80 years later marked the arrival of the Siemens SGT5-9000HL (Figure 3). It too runs at 3000 rpm, but that is where the similarities end. It has a nameplate rating of up to 593 MWe at ISO conditions making it officially the most powerful gas turbine in the world as of this writing.

Figure 3. The SGT5-9000HL is rated to deliver up to 593 MWe in simple-cycle operation, making it the largest nameplate rating of any gas turbine. It can produce 880 MWe in 1:1 combined cycle operation.

It boasts a simple cycle efficiency exceeding 43%. When placed into a 1:1 combined cycle operation, the efficiency jumps to greater than 64% and the power output to 880MWe. In terms of size, the Siemens giant has a footprint9 that is approximately the same as the Neuchâtel machine10 yet produces 150 times as much power. On the testbed, more than 6000 simultaneously monitored sensors11 were used in bringing the 9000HL machines from the drawing board to the market. The engine underwent first fire in April 2020 for the 60 Hz variant and the first installation of the larger 50 Hz version at the U.K.’s Keadby 2 combined-cycle plant underwent first fire in October 2021 and was handed off from Siemens to Keadby in mid- 2022.


The Trophy Case

Siemens is no stranger to owning the title of “world’s most powerful” when it comes to gas turbines. Today, the title is held by the 60 Hz variant, the SGT6-9000HL.12 And prior to this, the SGT5-8000H, released in 2008, managed to hold three world records13. The title has moved back and forth over the years and different manufacturers and the healthy competition therefrom keep pushing power outputs and efficiencies ever higher. Today, however, the SGT5-9000HL is poised to move into the top spot at the Keadby 2 power station where it will be operating in combined cycle service and capable of 880 MWe.

What We Monitor

Meggitt has a lengthy working relationship with Siemens and is the standard and preferred supplier of vibration monitoring systems and sensors along with combustion instability instrumentation on their industrial gas turbines in power generation service. The SGT-8000H family is monitored by our products and now, the SGT-9000HL.

As gas turbines get larger, the basic construction remains the same. The turbine itself has only two radial bearings and a thrust bearing – just like smaller gas turbines. The generator has two radial bearings – just like smaller generators. The number of combustors cans (can-annular technology) varies with the size of the engine and whether 50 Hz or 60 Hz variant. When placed in combined cycle configurations, the steam turbines are not markedly different either in terms of instrumentation. What of course does change is the amount of power produced by the gas turbine and any associated steam turbine if using the exhaust gas to make steam. A false trip or a missed trip means that huge amounts of power are at stake, perhaps in excess of 800MWe. We are very proud that Siemens has trusted our solutions for many years across their range of gas and steam turbines, and that trust continues all the way to their very largest of offerings: the SGT-9000HL family.


After 70 years, we have learned the many nuances of protecting machinery and monitoring its condition. And although we monitor thousands of machines around the world, collectively encompassing TW of power, there is still special significance in being entrusted with the world’s most powerful gas turbine.

In our next installment of this 3-part series, we’ll introduce you to Arabelle – the world’s largest steam turbine and our role in monitoring the entire family of Arabelles including the massive 1770 MW units destined for the Hinkley Point C nuclear station in the U.K.

In the meantime, we invite you to learn more about our offerings for both gas and steam turbines on our informative application pages and by contacting your nearest vibro-meter sales professional. You will also find our Practical Guide to Gas Turbine Monitoring a helpful resource, along with this article that examines combustion dynamics monitoring for gas turbines in greater depth.


1 UK patent #1833.

2 Landis, F. "gas-turbine engine". Encyclopedia Britannica, 15 Feb. 2023, Accessed 17 Feb 2023.

3 KWU (now Siemens) reportedly built a model of Barber’s gas turbine for the 1972 Hannover Fair.

4 Landmark #135: Neuchâtel Gas Turbine; Accessed 17 Feb 2023.

5 “The World’s First Industrial Gas Turbine Set – GT Neuchâtel: A Historic Mechanical Engineering Landmark” Alstom publication PSE/BGENE/WFDGTN07/eng/PSER3/06.07/CH/6245 (June 2007). we are/engineering history/landmarks/135-neuchatel-gas-turbine.pdf. Accessed 17 Feb 2023.

6 Langston, L.S., “Single Crystal Turbine Blades Earn ASME Milestone Status”, Machine Design, pp. 46-52, vol 90, Mar 2018. Accessed 17 Feb 2023.

7 This first use in the V84.3 was for corrosion resistance, not primarily firing temperatures. See also footnote 6.

8 Source: “Combined Cycle Power Plants” IMIA Working Group Paper 91 (15); pages 9 and 12, IMIA Annual Conference 2015, Merida (Yucatán), Mexico, 26-30 September 2015. Accessed 17 Feb 2023.

9 SGT5-9000HL: 13.3m L x 5.3m W x 5.5m H (core turbine only)

10 18m L x 5m W x 8m H. See reference in footnote 5 for dimensional diagram.

11 “A Decade In The Making – Siemens Energy HL-class Now Delivers Power To The Grid” Siemens Energy whitepaper, Oct 2020. Accessed 17 Feb 2023.

12 “Siemens Energy and Duke Energy’s gas power plant achieves GUINNESS WORLD RECORDS™ title” Press Release, Siemens Energy, 23 Aug 2022. Accessed 17 Feb 2023.

13 “One power plant – three world records”. Siemens brochure (2014) Accessed 17 Feb 2023.

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