What are the pros and cons of using 9Chrome steels when connecting a HRSG to a steam line?
A growing number of power producers have installed simple-cycle or combined-cycle CT power plants that employ 9Chrome steels (P91, P11, and P92) for piping and tubing applications. Until recently, P91 has been primarily used in Europe and Southeast Asia, because excess generating capacity discouraged new plant construction in the U.S. Recent energy shortages throughout the country have prompted renewed interest in P91 due to its unique qualities, which allow turbine owners to increase operating pressures and temperatures to achieve higher efficiencies. Additional benefits of P91 include enhanced creep performance properties and better strength-to-weight ratios, which reduce the required wall thickness compared to 2-1/4Cr1Mo or 1-1/4Cr1/2Mo steel. The resulting higher temperature gradient and lagging residual stresses enable better heat dissipation, which in turn reduces thermal fatigue. In addition, use of 9Cr steels lowers installation costs because they require less overall welding d
