2018 CPS Piping Services for CCGT Plants
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
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.)
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: