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With the increasing amount of renewable generation coming online to the North American power grid and the inherent variable nature of these generation sources, fossil fuel fired generation is being called upon to cycle more frequently. With the low natural gas fuel prices currently in the market, Combined Cycle gas generating units are carrying a large portion of this cyclic load following.

A Combined Cycle unit that can efficiently cycle can gain additional market revenue by capitalizing on higher market pricing opportunities.

These cycling activities will eventually take a toll on the generation equipment, especially the steam turbine and its components. Continual cycling subjects the equipment to heat stresses, especially the rotor, turbine blades and the turbine shell. If uniform temperatures are not maintained across the turbine shell and within the turbine casing, rubbing and binding may occur between the rotating and fixed turbine components.
Cyclic fatigue stresses will eventually lead to higher maintenance costs, lower reliability and the eventual failure of equipment.

A Turbine Warming System (TWS) is a cost effective way to alleviate many of the heat stresses and metal fatigue associated with cycling. A TWS will maintain a uniform temperature gradient across the entire turbine shell and alleviate component damage that occurs with differential expansion.

  • The TWS will also greatly reduce start times. Cold starts where a unit may be idle for 48 hours or more are theoretically eliminated. Warm starts of 24 hours or less are greatly reduced and hot starts are reduced to a lesser degree.
  • The length of time an operator spends heating the turbine components and the associated fuel burn is a major contributor to a generators start-up costs. These shorter start-up times and lower fuel burns also lead to lower emissions.
  • A TWS will maintain the steam turbine equipment at desired temperatures up to 700 degrees Fahrenheit at a minimal operating cost.
  • A TWS gives the unit operators a graphical view of the outer and inner temperatures across the turbine. The system is programmed with logic to control temperatures along with alarms and warmings for component failures.

Benefits


Direct Savings and ROI

A properly installed and maintained TWS has an expected life of 10 years or more. The investment to install the TWS creates an ROI for years to come.

  • Lower Overall Plant Operating Costs – an improvement in start-up heat rate up to 3% is possible
  • Emissions Cost Savings
  • Decreased Metallic Corrosion by maintaining equipment above Dew Point temperature

Decreased Thermal Stress Cracking

Installing the TWS will greatly reduce thermal stresses on the equipment and increase equipment life even beyond manufacturer’s Starting and Loading chart values. Cyclic fatigue stresses will eventually lead to higher maintenance costs, lower reliability and the eventual failure of equipment.

  • Maintains Components above Fracture Appearance Transition Temperature (FATT)
  • Reduced Cyclic Fatigue and Brittle Fracture Cracking

Reduced Start-Up Times

A key component of the start-up process is the amount of time necessary to match steam and metal temperatures within an acceptable temperature tolerance range. Cold starts where a unit may be idle for 48 hours or more, are theoretically eliminated. Warm starts of 24 hours or less are greatly reduced and hot starts are reduced to a lesser degree. The TWS solves the Start-Up problems by always maintaining the steam turbine in a “Hot” start condition.

  • Cold starts are eliminated
  • Maintains Warm or Hot Start Condition

Minimized Differential Expansion

Using the TWS, an Operator can control and maintain steam turbine metal temperatures in a “Hot” start condition. The system will also precisely control shell temperatures to avoid “humping” the shell and radial rubbing during start-ups. If uniform temperatures are not maintained across the turbine shell and within the turbine casing, rubbing and binding may occur between the rotating and fixed turbine components.

  • Increased turbine life
  • Reduced premature Blade Seal Wear

Services


Integration Services

The TWS includes stand-alone control system with one or more control screens. Optionally, PSI can assist with integration of TWS monitoring and/or control into existing Plant DCS.

Maintenance Service Agreement

Maintenance and Service Agreement available to extend parts and labor warranty to full 10 years for entire system.

  • Yearly inspection of all TWS components
  • Skilled labor provided for any event requiring blanket removal