Tetra Engineering
"Data to Decisions"

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Last Updated:
12-jan-07 15:44 CET

Tetra Engineering offers HRSG Inspections and Condition Assessments to assist O&M staff in identifying incipient problems so that they can take action before damage becomes severe. These are offered as either a: standard inspection, with a work scope that is suitable for annual outages such as an outage tied to a minor gas turbine inspection, or a comprehensive inspection that is scheduled during major gas turbine outages at longer intervals. Tetra Engineering does not offer HRSG repair services; therefore our recommendations to plant management are not biased towards encouraging unnecessary component replacement or other construction work.

We have inspected over 175 HRSG units from all major manufacturers at power plants worldwide. Our experience base assures that we are familiar with all damage mechanisms that might be encountered across the range of possible plant operating regimes and fuel types.

Standard Inspection and Condition Assessment

This comprises a detailed visual inspection to assess the current condition of the HRSG and a brief review of certain key aspects of the plant operating history. We evaluate the progression of known degradation/damage, search for indicators of new degradation and identify problem areas. We then recommend actions to mitigate/minimize component degradation to the plant staff.

The scope of inspection incorporates:

The optional UT thickness survey is performed at selected (accessible) components based on preoutage evaluation of high-risk locations. It includes wall thickness measurements on tube, header and connecting piping at locations in the HRSG where design reviews indicate components will be most susceptible to FAC.

The deliverable for the standard inspection is a report that clearly documents inspection results and that provides a succinct evaluation of unit condition. It identifies any changes from the last assessment, any current and incipient problem areas and recommended actions.

Comprehensive Inspection and Condition Assessment

This service is an extension of the Standard Inspection & Condition Assessment. It includes an in-depth review of design data, operating history and water chemistry logs prior to the inspection. In cooperation with the client, this is used to write an inspection plan that fully defines the inspection scope. This generally encompasses:

1. Detailed visual inspection of all accessible gas-side, waterside and external HRSG components and if requested, certain associated steam cycle equipment such as deaerators, condensers and power piping to steam turbine.
2. UT thickness survey of all areas that are potentially susceptible to wall thinning including, if requested, the associated external piping.
3. NDE surveys using an analytically prioritized inspection plan for key welds (tube/header, end cap, piping nozzles etc) using Magnetic Particle (MT), Dye Penetrant (PT), or UT flaw detection techniques.
4. Analysis of drum and gas-side deposits to identify eventual contaminant or corrosion issues.
5. A detailed condition assessment of the HRSG based on a comprehensive review of design and operating data.

The objective of the condition assessment is to identify any operational issues of concern with regard to evolution of the HRSG integrity, using the current condition as a starting point. The work can include a number of tasks analyzing unit condition and performance: evaluation of corrosion fatigue and creep-rupture life, determination of creep-fatigue limits on welds, damage susceptibility from condensate accumulation, waterside and gas-side deposition and corrosion rates, attemperator spray action, startup performance etc.

The deliverables are a final inspection report and an accompanying record of inspection data and photographs. The report will record the observations, identify key issues and provide recommendations for improvements. It will also give a list of inspection locations and recommended schedule for future inspections. As an option, the record of inspection data can be incorporated into a 3D visualization and knowledge management tool (CARDS). CARDS was developed by Tetra Engineering and couples plant O&M information and inspection data (photographs, NDE logs etc.) with a dynamic 3D visualization of the HRSG. It provides an interactive and easily distributed means for incorporating the historical, present and future inspection condition results for the HRSG.