Tetra Engineering
"Data to Decisions"

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Last Updated:
20-jan-06 11:29 CET

This service provides the HRSG owner with a comprehensive review of their operation in cycling service. The goal of the review is to provide clear, easily implemented recommendations to improve unit cycling operation. Plant procedures, design and operational data are reviewed and assessed for potential impact on HRSG component reliability.

Scope of Service
Engineers from Tetra visit the site to perform a walkdown, discuss plant operation with staff, and collect operating data from the DCS or data historian. The field visit is scheduled so that, if possible, a start (hot, cold or warm) can be witnessed. The team then reviews and assesses:

• HRSG design features and operating limits (metal temperatures, OEM prescribed ramp rates, etc.)
• Plant startup procedures for cold, warm and hot starts.
• Key plant controls for HRSG operation including steam temperature and drum level controls.
• Purge and drain procedures and controls
• Collected operating data

The work places special emphasis on improving control and operating aspects of condensate removal, purge and temperature control by spray and bypass. Another major emphasis is to identify potential improvements in water chemistry control during cycling operation as it impacts on component condition.

Weak points in the HRSG design (for example, susceptibility to fatigue, corrosion fatigue, damage due to economizer steaming, etc.) are identified as well as weaknesses in the design of spray systems, drains, baffles and supports. If on-line data from PI or another data historian is available for an extended period, Tetra will use our Event Filtering Software (EFS) to rapidly scan for potentially adverse conditions that merit attention. This aids the review in identifying operating scenarios that may not occur during every startup or shutdown.

Deliverable
The deliverable is a HRSG Cycling/Optimisation Report that presents recommendations for plant management based on the results of the cycling review. The recommendations can encompass:

• Changes to control logic or setpoints to minimize stress on HRSG systems.
• Changes to plant operating procedures to minimize stress on HRSG systems. This will include all startup options including lead and lag units and hot, warm and cold starts.
• Actions for potential reduction in unit startup time without impacting stress/damage limit.
• Areas of concern for HRSG auxiliary systems including power piping, drains, and water systems.