Tetra Engineering Group, Inc. has assisted many owners of natural gas-fired combined cycle plants with the development of effective Covered Piping Systems (CPS) Programs, Inspection Plans, Pipe Stress Analysis and Field NDT since the ASME adopted the new Code requirements for piping O&M in Section B31.1 Chapter VII in 2007.
Tetra has developed such programs for CCGT owners in the US, Canada, Mexico and the Middle East. They have been prepared for 'bubble' 2x1 design with F-class gas turbines as well as modern 1x1 fast-start units, plants with aeroderivative GTs and once-through steam generators as well as smaller units operated by municipal power companies, some of which are in cogeneration service.
Based on the latest B31.1 requirements, the CPS Program Plan is tailored to meet your requirements especially regarding the scheduling of NDT inspections over multiple outages to distribute costs and meet outage budget constraints
Covered Piping systems O&M Programs for CCGT Plants
Modern CPS Piping Programs have evolved from historical high energy piping (HEP) programs to address a host of CCGT-specific issues including: Grade 91 issues, turbine bypass and inter-stage attemperator piping thermal shock/quench and spray valve degradation, long term creep damage, flow accelerated corrosion damage to susceptible feedwater piping (spray supply, blowdown lines and HRSG interconnecting piping.)
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Some of the newest CCGT have as many as 4 desuperheater stations with dual HRH bypass and CRH bypass providing improved steam temperature control. These programs usually include the feedwater piping as well as LP Steam piping (which operates below the creep range) and auxiliary steam piping - if present. Stress analysis results and field walkdowns continue to be key elements of programs, but the focus today is on degradation specific inspection plans that go beyond the scope of radiant plant programs from the '80s which were geared to address the important needs of coal plant operators. Properly designed and constructed CCGT operate at conditions and stresses generally well below the corresponding values for radiant plants. However, two-shift cycling, merchant operations, 'chasing' renewables in markets dominated by wind and solar and long layups in cold weather climates can all result in early in life damage.
Root Cause Failure Analysis of CPS Piping, including interconnecting piping (for example, inter-stage attemperator piping), Grade 91 piping and carbon steel fittings and pipe sections has been a common request from our CCGT clients.
Fitness-for-Service evaluations using the ASME FFS-1/API-579 Rev. 2 methods provide effective means to determine whether a degraded component can remain in service until a longer outage is scheduled or if immediate repair, replacement or derating is required to maintain safe and reliable operation.
For more information on CPS Piping Programs, Field NDT Services or other CPS Piping related evaluations including Pipe Stress Analysis, contact:
Europe/Middle East/Africa/Asia: Andreas Fabricius at +33 (0)4 92 96 92 54 or at andreas.fabricius@tetra-eng.com
North/Central/South America: Peter Jackson at +1 860 651-4622 ext. 103 or at peter.jackson@tetra-eng.com
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Since 2007 the ASME B31.1 Power Piping Code has included Chapter VII, establishing mandatory requirements for Operation and Maintenance. The key elements of this program are discussed here, and require that Operators outline a detailed maintenance plan for their Covered Piping Systems (CPSs). The Code also requires that operators perform regular Condition Assessments of their CPS ensuring that relevant degradation mechanisms are being covered.
PipeVue 2.0 was developed by Tetra Engineering to store and organize large amounts of inspection data in one network-based solution, easy accessible for both plant operators as well as engineers planning yearly inspections.
Since 2007, the ASME B31.1 Power Piping Code has included mandatory requirements on the Operation and Maintenance (O&M) of Covered Piping Systems (CPS), previously called High-Energy Piping. The main concern is that the safety of these systems is very dependent on good O&M, which justifies its inclusion in the Construction Code. There is room for flexibility depending on individual circumstances but the responsibility is squarely laid on the Operating Company.
