HRSG Inspection Planning

Building a good inspection plan for the HRSG involves doing the following:

  1. Set the Time and General Schedule for Inspection
  2. Review Known Problems
  3. Identify and Obtain Required Records and Documentation
  4. Develop the Inspection Route
  5. Plan for Generating and Obtaining Permits
  6. Identify Access Requirements
  7. Coordinate with other work to be performed on HRSG during the outage: This is particularly important if outside contractors are involved. Site procedures may preclude confined space access by inspection personnel until these conflicting activities are complete.  Some examples of potential conflicts:
    • Installation of scaffolding, opening of internal baffles
    • Shot blasting/cleaning of tubes causes a dusty environment throughout the HRSG.
    • Carbon dioxide cleaning (blasting using solid pellets of CO2) creates an asphyxiating atmosphere which may be present throughout the boiler. 
    • Hot work (including cutting and welding) may preclude inspection in that area for some time as the surfaces remain hot
  8. Define Inspection Equipment Requirements
  9. Identify Other Special Requirements
  10. Plan for Inspection Completion and Closing Up of HRSG.
  11. Plan the Post-Inspection Review

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Known problems with the HRSG or incidents in the operating history that may have affected HRSG integrity since the last inspection should be carefully reviewed.  This should ideally be done with the involvement of appropriate plant staff.   For example, consult with the plant chemist to see if there were problems with the quality of the water chemistry at any time during the last operating period.  The pre-planning review is often forgotten or done in a perfunctory manner due to lack of time, and the result is an inspection plan that might not fully account for important issues [1]. 

Careful planning to assure easy and timely access will greatly facilitate the progress of the inspection.   Take the time to define what doors and manways need opening, which baffle and components need removal, setting the placement of scaffolding and skyclimbers, as well as their erection and disassembly.  Examples are locations where small scaffolding is required at drum decks or to access manways that are not accessible via platforms or locations where temporary modifications of existing structures are required to gain access (hand rail removal, temporary disassembly of structural supports such as gas baffles or other related structures).  Any special access requirements such as cutting of new access ports to facilitate inspection access and insulation removal should be identified as early as possible.

Confined space access is handled in accordance with site procedures at each plant. The criteria for fitness for duty, such as minimum wall thicknesses for pipes and tubes should always be clearly defined prior to inspection, so that rapid decisions can be made without delaying inspection work.  Requirements for inspection documentation should be laid out prior to the start of work. There should always be a review and assessment of the result of the inspection once the inspection report is completed.  This review should involve all interested staff and incorporate an assessment of any problems found during the inspection, development of plans for future inspections at this HRSG as well as sister HRSGs, and identification of any additional engineering work. 

References

[1] Jackson, P. Moelling, D. Malloy, J. Taylor, M. HRSG Inspection Planning Guide - Second Edition, 2006. ISBN 0-9719616-2-X

 

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Established in 1988, Tetra Engineering has more than 25 years experience providing solutions to the power industry. We specialize in solutions for HRSGs, conventional boilers & steam-cycle balance of plant.

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