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Our answer to changed operational requirements

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State-of-the-art features for your power plant to remain competitive

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.

 

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The perfect service for your plant

Four aspects of Flex-Power Services for your fossil power plant

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.

Start & Stop Performance

Measures for providing Power on Demand and enhancing the various start & stop performances can include:

  • Wet Compression for gas turbines
  • Rotor flexibility package for generators
  • Hot Start on the Fly for steam turbines

 

 

Steam Turbine Hot Start on the Fly

Solution

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Improved start-up concept with steam turbine Hot Start on the Fly

Some combined cycle power plants which were originally built as base load plants are now operating as peak load plants or as cycling plants with daily start-up. Hot starts after an overnight shutdown may need to be performed fast, using predictable and reliable measures to provide a high dispatch ability and in-market availability.

 

Siemens developed an innovative upgrade package for F-class combined cycle power plants, designed to significantly reduce the plant’s hot start times from e.g. 60 or more minutes down to a plant specific value of e.g., less than 40 minutes. This considerable improvement is based on a parallel start-up of the gas turbine and the steam turbine – also known as Hot Start on the Fly.

 

 

Benefits

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Potential benefits of improved plant start-up concept**

Depending on the operational limitations and requirements of your power plant, the benefits of the improved Hot Start on the Fly may include: 

  • The capability to provide virtually full MW loading in as little as 40 minutes, which may open up new revenue opportunities like peak shaving
  • The automated start-up procedure which can help you to save fuel and gain a higher efficiency during start-up
  • Reduced gas turbine CO emissions during start-up

 

 

Gas turbine start-up and loading without load hold to wait for the steam turbine start-up:

  • Early steam turbine roll-off with first steam production (“colder steam“) at low pressure
  • Steam turbine run-up to synchronized speed, synchronization and loading during continuous pressure increase
  • Lower steam production because of higher pressure ramp rates, to minimize start-up losses by reduced steam dump to the condenser
  • Early closing of high pressure/intermediate pressure bypass valves, possibly before the gas turbine is at base load

 

** Example for illustration. Actual results may vary depending on plant conditions and other factors.

 

 

 

Scope

Siemens Flex-Power Services supplies an integral solution tailored to the specific situation and configuration of the power plant.

 

Our Hot Start on the Fly concept includes:

  • Modified high pressure / hot reheat steam temperature control and modified unit controls
  • New high pressure and hot reheat bypass control philosophy
  • Modifications in the steam turbine controller and new balance of plant system signals
  • Improved gas turbine control promoting usage of maximum possible load ramps over a wide operating range
  • Implementation of logic changes into the plant’s digital control system
  • Stress and fatigue monitoring systems for the steam turbine and the heat recovery steam generator
  • Re-commissioning, validation and tuning
  • Operator training and documentation

 

 

Steam Turbine Advanced Fast Loading

Solution

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Monitoring of optimized ST start-up process

Advanced Fast Loading for steam turbines is one of our solutions to improve an operating combined cycle power plant in flexibility and efficiency. 

 

It has become more and more necessary for many existing units to be prepared for a fast start-up and cycling operation in the full power range from full load to minimum part load. As many gas turbines in combined cycle power plants have already been modified for faster start gradients and loading, higher ramp rates need to be provided for steam turbines as well. This may be essential to achieve the desired plant start-up times and loading rates. 

 

Siemens steam turbines are accelerated with a fixed speed transient and loaded based on a maximum load transient in accordance to the need of the entire power plant. Siemens developed an innovative upgrade package which may incorporate the increase of speed and load transients of the steam turbine by up to 100%. This optimization helps to shorten the steam turbine start-up times. 

 

 

Benefits

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Benefits of the Advanced Fast Loading options (for illustration purposes only)

 

In terms of reliability and efficiency the product is designed to improve the plant start-up performance. It may be an important advantage for your plant’s responsiveness to volatile energy markets.


With Steam Turbine Advanced Fast Loading Siemens offers you one of its latest methods to shorten the start-up process based on the specific turbine type. Implementing the Steam Turbine Advanced Fast Loading, further improvements may include:

  • Fast response for flexible operation
  • More efficient start-up
  • Increased revenue due to a more efficient start-up process
  • Reduced emissions during start-up
  • Full advantage of gas turbine upgrades

 

The final benefit depends highly on the plant configuration and plant optimization status.

 

 

Scope

 

To improve start-up performance and flexible load operation Steam Turbine Advanced Fast Loading is based on a turbine control update. Depended on this, Siemens will engineer the recommended modification of instrumentation and control. This may also include changes to the unit master control system.

 

In addition, mechanical analysis of the steam turbine will be performed to allow for steam turbine operation with higher transients. The respective modifications of the I&C system can be implemented at an offline period such as a weekend shut down.

 

 

Degassed Conductivity for faster start-up of Combined Cycle Power Plants

Solution

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Proposed Degassed Conductivity sampling points of Siemens Combined Cycle Power Plants (CCPP)

Considering fuel costs and emission parameters, any decrease in time between start-up and full load can be significant. Shorter start-up times are essential to addressing these considerations, and a key to achieving those is shorter waiting times for acceptable steam quality.

 

Our Flex-Power Services™ product Degassed Conductivity can help reduce steam turbine operating hours in the respective action levels due to dissolved carbon dioxide and decrease the consumption of allowable total operating hours of those action levels.

Benefits

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Degassed Conductivity – potential benefit chart*

A shorter start-up time may be an important advantage of responsiveness to the market and can help to reduce the start-up costs for combined cycle power plants. With Flex-Power Services™ Degassed Conductivity, Siemens can offer its latest method designed to help shorten start-ups, especially cold starts.

 

Using fast start-up packages as well as Degassed Conductivity, the start-up time of a combined cycle power plant and the waiting time for steam purity can be significantly reduced.

 

Benefits can include:

  • Increase in flexibility as a consequence of a more detailed steam purity analysis
  • More efficient operation due to less fuel consumption
  • Reduced gas turbine emissions during start-up

 

* Conceptual illustration for information only. Not to scale. Actual experience may vary.

 

 

Scope

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Arrangement of modified sampling

Degassed Conductivity is a method used to analyze steam purity and determine whether the steam can be delivered to the steam turbine or the condenser. Degassed Conductivity makes it possible to eliminate the contribution of carbon dioxide to the Acid Conductivity (AC).

 

The newly developed method controls the steam purity and distinguishes between the corrosive contaminants and less harmful carbon dioxide by measuring the Degassed Conductivity. The analyzer re-boils the sample downstream of the caution column to remove carbon dioxide. Automatic compensation of the boiling point for air pressure changes and a sample flow measurement are features integrated in the system.

 

In addition to the hardware distribution, other services provided include:

  • Chemical assessment of plant steam conditions
  • Evaluation of chemical operation mode which can lead to recommendations for improvements of the sampling system
  • Commissioning of sampling system and training of plant personnel

Fast Release to Nominal Speed

Solution

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Siemens high pressure barrel type steam turbine

One of our Flex-Power Services™ solutions to improve your combined cycle Power Plants flexibility and efficiency is Fast Release to nominal Speed.
For a reliable and gentle ramp up of the steam turbine to nominal speed, superheated steam must be present in all areas of the barrel type turbine. Therefore various pressure and temperature measurements are evaluated during warm-up speed, before the operator is allowed to release to nominal speed. 

 

The current measurement points are in the middle of the HP casing (top and bottom measurement), and typically have a longer time delay which is not optimal where a faster start-up process may be desired.

Fast Release to Nominal Speed incorporates a quicker release criterion which allows shortened gas turbine part load operation, which can lead to less fuel consumption and gas turbine CO emissions during the start-up process.

 

 

Benefits

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Fast Release to Nominal Speed – potential benefit chart*

A shorter start-up time may be an important advantage for your plant’s responsiveness to the volatile energy market and may help reduce the start-up costs for combined cycle power plants.

 

Benefits can include:

  • Increase in flexibility as a consequence of shortened start-up process
  • More efficient operation due to less fuel consumption
  • Reduced gas turbine CO emissions during start-up

 

* Conceptual illustration only!

 

 

Scope

Comprehensive evaluations are done to yield to the identification of new, faster responding measuring points to control the steam temperatures within the HP turbine. Several changes in the start-up logic and user interface diagrams as well as in the operation manual are also part of the upgrade.

 

The new concept includes hardware and software changes which may be implemented at a minor gas turbine inspection or outage of similar duration. The product is available as a retrofit for the Siemens fleet and may be combined with other Flex-Power Services™ to help further improve the cold start performance of the power plant.

 

 

Modified Pre-Warming Concept for Faster Cold Starts

Solution

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Combined IP/LP steam turbine

Flex-Power Services™ provides a modified pre-warming concept for shafts of combined intermediate pressure and low pressure (IP/LP) steam turbines with reverse flow directions of the IP and LP blade path. An improved pre-warming concept is gaining increasing importance, as many power plants are experiencing extended durations between operation periods. In many countries, especially in Europe, this leads to a rising number of steam turbine cold starts (typically occurring after more than 5 days out of service) 

 

 

Benefits

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Benefit of the Modified Pre-Warming Concept (conceptual illustration only)

Implementing the Flex-Power Services™ product Modified Pre-Warming Concept for Faster Cold Starts may reduce the cold start time of the steam turbine. Depending on the operational limitations and requirements of your power plant, the benefits of the improved pre-warming concept may include: 

  • Increased responsiveness to the transmission system operator (TSO) due to shorter start-up time
  • Increased revenue due to a more efficient start-up process
  • Reduced emissions during start-up

 

 

Scope

 

The Modified Pre-Warming Concept for Faster Cold Starts not only consists of software adaptions but also includes a previous extensive engineering study analyzing the condition of the turbine shaft based on:

  • Original equipment manufacturer (OEM) quality assurance documentation
  • The operational history of the unit (e.g. number of starts)

 

 

The analysis may be supported by ultrasonic testing of the shaft.

The concept comprises several I&C changes of the steam turbine automation software. The number of starts using the modified pre-warming is registered in an internal start-up counter which is part of the modification. When the number of starts predetermined through the engineering study is reached, the original pre-warming sequence logic is designed to automatically reactivate until the shaft can be re-qualified by ultrasonic testing.

 

 

Gas Turbine Wet Compression Modernization

Flexibility Improvements for Power Plants - Site Assessment

Solution

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View of a SCC5-4000F single shaft combined cycle power plant

To minimize the gap between the original intended operation mode and actual requirements, Siemens can evaluate the current demands on your plant and develops specific solutions tailored to your needs.
A customized improvement recommendation can help to analyze and optimize the interaction of the existing hardware and software as well as your manual operation. 

 

A general site assessment starts with a plant walk down.
Followed by detailed analyses, required in order to provide tailor-made recommendations for improvements specific to the power plant’s needs. Based on these recommendations experienced Siemens engineers analyze the plant and discuss their general findings with the plant management and operational personnel.

 

Their goal is to evaluate:

  • Requirements and tasks
  • Operational limitations
  • Future operational scenarios
  • Historic operation regimes

 

 

 

Back in the office Siemens experts analyze the collected information and identify options for providing more operational flexibility through, e.g. Faster start-ups, Faster load ramps or Enhanced operating regimes, e.g. lower part load operation.

 

 

 

Benefits

The implementation of the recommended improvements determined within a Site Assessment can result in the following benefits:

  • More economical use of available lifetime
  • Faster start-ups and shut-downs
  • Improved load ramps
  • Reduced minimum part load
  • Increased reliability and availability
  • Increased flexibility and profitability

 

 

Scope

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Siemens experts in discussion with customer

We provide our recommendations and engineering expertise based on customer stated needs. It is up to you to decide to implement all recommendations, or just those which are considered. Some of our recommendations can be an individually developed solution, but in most cases they will be part of the Siemens Flex-Power Services™ product portfolio. 

 

Carrying out a Site Assessment can provide you with recommended and preferred options for upgrading your power plant in a cost effective way to help increase is operational flexibility. As a result, we provide:

  • A comprehensive report outlining potential improvement areas
  • Recommended measures
  • Information to help plant management assess the potential economics of the recommended upgrade options

 

 

 

 

Grid Services

Measures for enhancing Grid Services, like allocation of peak power and fast load gradients, can include:

  • Grid code studies (e.g. ENTSO-E)
  • Turn Up for gas turbines
  • Fast Wet Compression for gas turbines
  • Wet Compression for gas turbines

 

Gas Turbine Wet Compression Modernization

Turn Up Upgrade for Siemens Gas Turbines

Fast Wet Compression for Siemens Gas Turbines

Flexibility Improvements for Power Plants - Site Assessment

Solution

image
View of a SCC5-4000F single shaft combined cycle power plant

To minimize the gap between the original intended operation mode and actual requirements, Siemens can evaluate the current demands on your plant and develops specific solutions tailored to your needs.
A customized improvement recommendation can help to analyze and optimize the interaction of the existing hardware and software as well as your manual operation. 

 

A general site assessment starts with a plant walk down.
Followed by detailed analyses, required in order to provide tailor-made recommendations for improvements specific to the power plant’s needs. Based on these recommendations experienced Siemens engineers analyze the plant and discuss their general findings with the plant management and operational personnel.

 

Their goal is to evaluate:

  • Requirements and tasks
  • Operational limitations
  • Future operational scenarios
  • Historic operation regimes

 

 

 

Back in the office Siemens experts analyze the collected information and identify options for providing more operational flexibility through, e.g. Faster start-ups, Faster load ramps or Enhanced operating regimes, e.g. lower part load operation.

 

 

 

Benefits

The implementation of the recommended improvements determined within a Site Assessment can result in the following benefits:

  • More economical use of available lifetime
  • Faster start-ups and shut-downs
  • Improved load ramps
  • Reduced minimum part load
  • Increased reliability and availability
  • Increased flexibility and profitability

 

 

Scope

image
Siemens experts in discussion with customer

We provide our recommendations and engineering expertise based on customer stated needs. It is up to you to decide to implement all recommendations, or just those which are considered. Some of our recommendations can be an individually developed solution, but in most cases they will be part of the Siemens Flex-Power Services™ product portfolio. 

 

Carrying out a Site Assessment can provide you with recommended and preferred options for upgrading your power plant in a cost effective way to help increase is operational flexibility. As a result, we provide:

  • A comprehensive report outlining potential improvement areas
  • Recommended measures
  • Information to help plant management assess the potential economics of the recommended upgrade options

 

 

 

 

Minimum Part Load

Measures for the reduction of the Minimum Part Load consider emission objectives and efficient plant operation and can involve, for example:

  • Turn Down and Low Load Turn Down for gas turbines
  • New high pressure barrel with an interstage valve for steam turbines

 

Modified Steam Turbine Valve Staggering for Improved Part Load Performance

Solution

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Changes to the unit master control system may be necessary.

One of our solutions to improve your operating combined cycle power plant flexibility and efficiency is Modified Steam Turbine (ST) Valve Staggering in combined cycle power plants (CCPPs) with more than one gas turbine feeding the steam cycle. The Modified ST Valve Staggering upgrade is designed to support lower load operation and to reduce loss of efficiency in this operating condition.

 

If a CCPP in multi gas turbine (GT) configuration operates with one gas turbine only and reduces the gas turbine power to a certain level, typically the main steam pressure controller starts to throttle the main steam control valves to stabilize the pressure. Due to valve staggering, the reheat control valves start to close, as it was intended with respect to turbine start up performance. The current standard valve staggering setup leads to high HP exhaust temperature and reduced efficiency during low load operation. An opening of intermediate pressure bypass stations or a turbine shutdown caused by high pressure exhaust temperature can also occur.

 

The Modified ST Valve Staggering introduces a new logic which disconnects the IP control valves from the output of the main steam pressure controller.

 

 

 

Benefits

The product is designed to improve reliability and efficiency in part load operation and may allow a decreased minimum load operation of the CCPP in cases with one GT in operation only.

 

Benefits can include:

  • Increased part load efficiency
  • Less throttling of reheat control valves
  • Reduced HP exhaust pressure and temperature during part load operation
  • Increased reliability due to lower risk of tripping on high exhaust temperature
  • Extended operating range with reduced minimum part load

 

 

Scope

The Modified ST Valve Staggering is a process and controls upgrade designed to improve part load performance. Due to the large variety of plant configurations an assessment of the current part load operation is the first part of the scope leading to recommended process changes for steam turbine and balance of plant.

 

Based on this, Siemens will engineer the recommended modification of instrumentation and control. This may also include changes to the unit master control system.

The final part of the scope is the implementation of the enhancements which could be executed during a relatively short shutdown period (possibly during a weekend shut down).

 

 

Flexibility Improvements for Power Plants - Site Assessment

Solution

image
View of a SCC5-4000F single shaft combined cycle power plant

To minimize the gap between the original intended operation mode and actual requirements, Siemens can evaluate the current demands on your plant and develops specific solutions tailored to your needs.
A customized improvement recommendation can help to analyze and optimize the interaction of the existing hardware and software as well as your manual operation. 

 

A general site assessment starts with a plant walk down.
Followed by detailed analyses, required in order to provide tailor-made recommendations for improvements specific to the power plant’s needs. Based on these recommendations experienced Siemens engineers analyze the plant and discuss their general findings with the plant management and operational personnel.

 

Their goal is to evaluate:

  • Requirements and tasks
  • Operational limitations
  • Future operational scenarios
  • Historic operation regimes

 

 

 

Back in the office Siemens experts analyze the collected information and identify options for providing more operational flexibility through, e.g. Faster start-ups, Faster load ramps or Enhanced operating regimes, e.g. lower part load operation.

 

 

 

Benefits

The implementation of the recommended improvements determined within a Site Assessment can result in the following benefits:

  • More economical use of available lifetime
  • Faster start-ups and shut-downs
  • Improved load ramps
  • Reduced minimum part load
  • Increased reliability and availability
  • Increased flexibility and profitability

 

 

Scope

image
Siemens experts in discussion with customer

We provide our recommendations and engineering expertise based on customer stated needs. It is up to you to decide to implement all recommendations, or just those which are considered. Some of our recommendations can be an individually developed solution, but in most cases they will be part of the Siemens Flex-Power Services™ product portfolio. 

 

Carrying out a Site Assessment can provide you with recommended and preferred options for upgrading your power plant in a cost effective way to help increase is operational flexibility. As a result, we provide:

  • A comprehensive report outlining potential improvement areas
  • Recommended measures
  • Information to help plant management assess the potential economics of the recommended upgrade options

 

 

 

 

Maintenance Flexibility

Measures for enhancing Maintenance Flexibility can include:

  • Reduced cool down times for gas turbines, steam turbines and generators
  • Extended scheduled inspection intervals for gas turbines, steam turbines and generators
  • Advanced component preservation concepts

 

Fast cooling of steam turbines

Solution

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Longitudinal section through an SST5-5000

Through extensive analysis, Siemens is able to provide Fast Cooling of Steam Turbines which could result in maintenance beginning significantly sooner than with traditional cooling methods and thus has the potential to get your power plant back online faster.

 

Cool down gradients are determined using the finite element method, to help protect against excessive thermal distortion and differential expansion. Existing temperature measuring points are used to monitor the cool down gradients. This helps to maintain the recommended temperature limits during a fast cool down. 

 

During Fast Cooling, the existing or the retrofitted condenser air removal system is used to draw air from the turbine hall through the blade path of the turbines, and into the condenser, where it is ultimately exhausted from the system. This air flow allows for a greater amount of heat to be removed from the components and for the steam turbine to cool down more quickly. 

 

 

 

For scheduled shutdowns the fast cooling process is divided into the following steps:

 

Operational cool down of turbine

Prior to the plant shutdown, main steam/ reheat steam temperatures are reduced to the minimum allowable value in accordance with allowable limits and protection criteria for the plant. Reducing the temperature during operation shortens the overall cool down time due to the lower starting temperature of the fast cooling process.

 

Natural cooling

Once steady-state temperature conditions have been achieved with reduced steam temperatures, the steam turbine is shut down. While on the turning gear, the turbine enters a natural cooling phase to permit the temperature differentials within the steam turbine to reach an equilibrium state.

 

Fast cooling with ambient air

At the end of the natural cooling phase for the steam turbine, the nozzles provided for connecting dehumidifiers at the admission control valves are opened and the vacuum pumps are switched on. This draws in ambient air via the control valves, which passes through the turbine blade path. The air flow is regulated using the control valves. Air is drawn in until a target temperature is reached.

 

 

 

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Temperature curve for various cool down procedures

Benefit

 

Fast Cooling is a reliable way of saving up to 5 days of cool down time compared to natural cooling.

 

 

Our Fast Cooling solution offers the following potential advantages:

  • Reduction of overall outage times for inspection
  • Power plant specific optimization
  • Increased availability through shorter cool down times at no risk to the turbine

 

 

 

 

 

Scope

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Temperature distribution at the beginning and end of fast cooling procedure

Detailed analyses are for the cool down process taking into account material strength limits, plant specific operating variables and usage factors.  

For turbines already equipped with the forced cooling system, different optimizations are possible. These provide further shortening downtimes as well as simplified handling: 

 

Automation

The degree of automation can be increased at a suitable steam turbine instrumentation and control system. The positioning of the control valves for the adjustment of the air flow rate is achieved by a control circuit.

 

Process optimization

A system-specific check of the existing procedure is carried out with the aim to optimize the process. This may lead to higher permitted cool down transients.

 

Hardware modification

Measures may be proposed for the improvement of the condenser vacuum during the air intake phase.

 

 

 

 

Flexibility Improvements for Power Plants - Site Assessment

Solution

image
View of a SCC5-4000F single shaft combined cycle power plant

To minimize the gap between the original intended operation mode and actual requirements, Siemens can evaluate the current demands on your plant and develops specific solutions tailored to your needs.
A customized improvement recommendation can help to analyze and optimize the interaction of the existing hardware and software as well as your manual operation. 

 

A general site assessment starts with a plant walk down.
Followed by detailed analyses, required in order to provide tailor-made recommendations for improvements specific to the power plant’s needs. Based on these recommendations experienced Siemens engineers analyze the plant and discuss their general findings with the plant management and operational personnel.

 

Their goal is to evaluate:

  • Requirements and tasks
  • Operational limitations
  • Future operational scenarios
  • Historic operation regimes

 

 

 

Back in the office Siemens experts analyze the collected information and identify options for providing more operational flexibility through, e.g. Faster start-ups, Faster load ramps or Enhanced operating regimes, e.g. lower part load operation.

 

 

 

Benefits

The implementation of the recommended improvements determined within a Site Assessment can result in the following benefits:

  • More economical use of available lifetime
  • Faster start-ups and shut-downs
  • Improved load ramps
  • Reduced minimum part load
  • Increased reliability and availability
  • Increased flexibility and profitability

 

 

Scope

image
Siemens experts in discussion with customer

We provide our recommendations and engineering expertise based on customer stated needs. It is up to you to decide to implement all recommendations, or just those which are considered. Some of our recommendations can be an individually developed solution, but in most cases they will be part of the Siemens Flex-Power Services™ product portfolio. 

 

Carrying out a Site Assessment can provide you with recommended and preferred options for upgrading your power plant in a cost effective way to help increase is operational flexibility. As a result, we provide:

  • A comprehensive report outlining potential improvement areas
  • Recommended measures
  • Information to help plant management assess the potential economics of the recommended upgrade options

 

 

 

 

 

 

 

Technical papers for download

Examples of successful projects

Watch the videos about our international reference projects.

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Get in touch

Get in touch with us to find the perfect application.