Turn Down

Valid for following frames: SGT5-4000F (V94.3A), SGT6-4000F (V84.3A)

  • Reduced minimum part load with lower carbon monoxide emissions

  • Increased combined cycle efficiency in part load operation

General Product Information

Enhance your part load capabilities

Our top priority at Siemens is to provide outstanding, responsive service solutions to help you improve your operating plant competitiveness and profitability. As part of our ongoing commitment to meet the changing requirements of your operating assets, we offer the latest technology to help to enhance your operating plant capability and flexibility as part of Siemens Flex-Power Services™. One of our modernization products is the Turn Down upgrade.

Siemens offers the Turn Down upgrade as an innovative solution designed to further reduce the compressor mass flow at part load and therefore to reduce the minimum part load where carbon monoxide emission requirements can be met.

The implementation of the Turn Down upgrade is designed to help increase efficiency for combined cycle plants in part load operation with a reduced minimum part load with lower carbon monoxide emissions and almost constant gas turbine exhaust temperature. The resulting expanded operating range is achieved by decreasing the compressor mass flow with increasing the adjustable range of the inlet guide. The actual minimum part load depends on your site specific conditions and the desired carbon monoxide emission level.

The high turbine exhaust temperature level allows the steam turbine to be in operation with the highest efficiency possible.

The Turn Down upgrade provides significant performance advantages and offers attractive financial payback options.

Your benefits

The Turn Down upgrade offers you a clearly technical and monetary quantifiable benefit and can be a cost-effective means to help you improve the overall performance of your gas turbine plant.


Benefits may include: 

  • Reduced minimum part load with lower carbon monoxide emissions at part load (depending on site specific configuration and desired carbon monoxide emission level) 
  • Increased combined cycle efficiency in part load operation
  • Lower fuel consumption (cost) during negative spark spread operation
  • Increased operating range

The Turn Down upgrade can be combined with other modernizations such as the Compressor Mass Flow Increase or the Hydraulic Clearance Optimization.

The Turn Down upgrade is state-of-the-art for new Siemens gas turbines.

Scope of Supply

The Turn Down upgrade from Siemens is just one of the many innovative packages available.



The scope of this upgrade includes: 

  • New linearization unit for Inlet Guide Vane
  • New Inlet Guide Vane position sensor with extended operating range
  • Modification of Inlet Guide Vane ring (including new scale and new bolts for bearing blocks) 
  • Detailed engineering and implementation of instrumentation and controls modifications related to the gas turbine

We recommend a major outage for implementing the Turn Down upgrade. We offer a full range of field service capabilities to help you manage your maintenance and outage schedules.

Flex Power Services

The global energy market is changing due to increasing renewable power generation and decreasing power prices. This leads to new operating profiles with higher flexibility requirements for many fossil power plants. To answer this demand, Siemens developed Flex-Power Services™ for a wide range of changed operational requirements. 

Flex-Power Service provides hard- and software solutions as well as studies and plant assessments. Due to the nature of the changing operational requirements, the solutions will often be influenced by the overall plant rather than individual components only. Therefore, Siemens develops solutions considering the integration of e.g. gas turbine, heat recovery steam generator, steam turbine and generators in a combined cycle power plant. Flex-Power Services can in many cases be provided as a retrofit for the Siemens service fleet and combined with other modernizations. Implementing these state-of-the-art features can help power plant components remain reliable and increase the competitiveness of the plant in the changing energy market.


Learn more about Flex Power Services

Customer Extranet Portal

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For owners/operators we offer further information on your equipment. Please register to the Siemens Power Generation Services Customer Extranet Portal.

Siemens Power Generation Services Customer Extranet Portal