HRSG Inspection Frequency

Effective maintenance scheduling and planning is critical to completing required work during outages and preventing minor problems from expanding to major problems and possibly forced outages. Approaches to maintenance scheduling and planning vary from site to site.  Today, the general emphasis is on preventive maintenance activities that are timed to prevent forced outages due to component degradation.  A combination of planned part replacements and inspection of parts not routinely replaced is the basis for an effective maintenance program. Some HRSG components are relatively difficult to repair or modify and require coordination between several organizations (plant staff, OEM, contractors, insurance inspectors, etc).  Because the schedule for HRSG maintenance is dictated by GT maintenance schedules, there are typically limited opportunities to perform comprehensive inspections of component conditions [1].  The statutory inspections have only a minor amount of scheduling leeway (usually 3-6 months.)  The Authorized Boiler Inspector for the plant’s insurance company is responsible for these inspections.  They typically include potential high loss components including the drums, safety valves and other pressure parts such as an external deaerator tank. 

Because more HRSGs are operated in cycling service, the Equivalent Operating Hour (EOH) approach to scheduling HRSG maintenance provides a useful basis for determining when to allocate resources to tasks.  EOH is the basis used by the major GT vendors to schedule GT maintenance activities.  Extension to scheduling HRSG maintenance, particularly specialized inspections, is straightforward.  The approach is amenable to integration with plant data available from the DCS, providing a schedule that is continually adjusted based on varying plant operation



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