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The next generation of advanced air-cooled gas turbines

Our HL-class gas turbines are paving the way to the next level of efficiency and performance.

Our HL-class gas turbines are paving the way to the next level of efficiency and performance. Derived from proven H-class technology in an evolutionary development step, the next generation of advanced air-cooled gas turbines uses a series of new, but already tested technologies like super-efficient internal cooling features for blades or vanes and an advanced combustion system to increase firing temperature.


The result:

A technology carrier to the next level with a combined cycle efficiency beyond 64%, with a midterm goal of even higher efficiencies. The HL-class consists of two engines: The SGT5-9000HL for 50 Hz, and the SGT6-9000HL for 60 Hz.

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Highlights of the SGT5-9000HL

The gas turbine is capable of world-class fast cold starts and hot re-starts due to the light and stiff rotor with internal cooling air passages and free thermal expansion of rotor and casing parts during transients. Hydraulic Clearance Optimization (HCO), an active clearance control,  ensures robustness and low turbine degradation at start-up. GT ramp-up rate 85 MW/min.

The advanced can-annular combustion system with dual fuel capability allows for higher firing temperatures and more operational flexibility. 25 premix burners improve the fuel/oxygen mixing. The ACE combustion system allows for GT turn-down to 21% minimum environmental load.

All turbine blades and vanes are equipped with an innovative multi-layer thermal barrier coating. This leads to higher combined cycle efficiency due to less cooling air consumption and reduced operational costs due to higher blade robustness.

The HL-class has been designed to minimize outage times. Rotor de-stacking can easily be done on site thanks to the Hirth-serrated disc assembly. All rotating compressor and turbine blades can be replaced without rotor lift or rotor de-stacking. Turbine blade 1 and turbine blade 4 are removable without cover lift. With 33kEBH service intervals the service concept is very competitive.

Due to proven and validated package and plant concepts the HL-class can easily be integrated in our power plants for simple cycle or combined cycle operation. This enables fast project execution. More than 50,0000  hours are saved on site due to modularized design and pre-engineered solutions.

The new HL-class is based on the reliable engine architecture of the SGT-8000H series with design features that have proved reliability in operation for years:


  • Hydraulic Clearance Optimization (HCO)
  • Single tie bolt with Hirth serration
  • 4-stage air-cooled turbine
  • Can-annular combustion system
Pratyush Nag

SGT-9000HL: A dream comes true …

Personal reflections after one year of testing: “I would be lying if I said I didn’t hold my breath during that first start-up a year ago. In some ways, it felt like I was holding my breath for five years, building up to that moment. What a thrill it was to see all burners lit up, the first time we tried

When experience meets evolutionary innovation

Based on proven design and relying on the vast fleet experience of the SGT-8000H series, the new SGT5-9000HL combines the best of past experience with newly developed technologies. Thus, efficiency and performance are pushed to the next level.
The HL-class consists of two engines: The SGT5-9000HL for 50 Hz, and the SGT6-9000HL for 60 Hz. A modular design approach allows for a substantial number of common parts.

The  HL-class is designed for high operational flexibility and has a joint DNA with the proven Siemens H-class:

  • Air-cooled 4-stage turbine
  • Steel rotor / Hirth serration / single tie bolt design
  • Hydraulic Clearance Optimization (HCO)
  • Can-annular combustion system

Tested technologies for higher efficiency and performance

To achieve top performance and efficiency levels, the HL-class turbines are operating at highest combustion temperatures with an advanced combustion system.
An innovative multi-layer thermal barrier coating and super-efficient internal cooling features are protecting turbine blades and vanes while reducing the need of cooling air.
Additionally, advanced 3D blading leads to higher aero efficiency in the compressor.  A free-standing, internally cooled turbine blade 4 reduces exhaust losses and allows for higher exhaust temperatures to enhance the water-steam cycle.

Plug-and-Play power core

Siemens Energy has re-invented the methodology for plant construction with a modular Power Core™.

The Power Core™ consists of prefabricated Siemens Energy Solution Blocks and prefabricated pipe racks. These plug-and-play blocks are fabricated and tested in a controlled manufacturing environment and delivered to site as large modules which can be lifted into place for assembly. This results in increased safety on site, accelerated schedules, less dependence on the availability of skilled local labor and in the end lower project risk.

HL-class power plants are based on one or more HL-class gas turbines and can achieve more than 64% efficiency in combind cycle operation:


SCC5-9000HL 1x1: 880 MW

SCC5-9000HL 2x1: 1,760 MW

Designed for low maintenance costs and short outage times

 All components are designed with high focus on optimized LCOE, highest availability and serviceability. Several service features are supporting this.

  • All rotating blades replaceable without rotor lift/rotor de-stacking
  • Easy rotor de-stacking on site due to disc assembly with Hirth serration and central tie rod
  • All turbine vanes and blades replaceable without rotor lift; vane 1, blades 1 & 4 replaceable without cover lift

Tremendous service fleet experience and continuous development result in a competitive service concept with 33,000 Equivalent Base Hours (EBH) / 1,250 Equivalent Starts (ES).

Fuel flexibility matters

The SGT6-9000HL runs on natural gas, LNG, distillate oil, or other fuels. The engine is equipped with DLE burners and has the capability to burn up to 50 vol% of hydrogen (H₂).

Designed to fullfil environmental requirements

While reaching highest levels of performance and efficiency, the HL-class is still complying with NOx and CO regulations.

NOx emissions: Down to 2 ppmvd (with SCR), or ≤25 ppmvd (without SCR).


Testing the big one – Insights into test sites of HL-class gas turbines

Efficiency, flexibility and hydrogen capability are key levers in driving the decarbonization of the energy industry – which also makes the HL-class a future-proof gas turbine. Get exclusive insights into HL-technology – close to reality at the Duke Energy’s Lincoln Combustion Turbine Station, a key testing facility for Siemens Energy’s largest HL-class gas turbine and be part of the virtual tour.

Technical data

Technical data for the SGT5-9000HL

Performance data for simple cycle power generation

Simple cycle ratings are  gross at ISO conditions natural gas fuel. Actual ratings will vary with project specific conditions and fuel.

Performance data for combined cycle power plant

Combined cycle ratings are net at ISO conditions natural gas fuel. Actual ratings will vary with project specific conditions and fuel.

Physical dimensions and weight

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Find out more about our gas turbine offerings

In our download section, you can find brochures, technical papers, and more. Or you can contact us directly for specific inquiries.

Siemens Energy HL-class gas turbines are based on proven H-class technology

Around 85 Siemens Energy H-class turbines in commercial operation, with more than 2 million fired fleet hours. Overall, about 100 units are under contract.
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Fast-ramping peakers support solar and bridge the way to net zero

Our customer Duke Energy is benefitting from the SGT-9000HL’s exceptional ramp-up capability, efficiency, and performance. Discover more about how this amazing turbine was developed, and how it fits into one energy provider’s plan to reduce carbon emissions while delivering reliable power. 

Do you have a question regarding our products, solutions and services?

Contact us