超超临界机组“四管”选用弯管或弯头的探讨

针对1 000MW超超临界机组主蒸汽管道、低温再热蒸汽管道、高温再热蒸汽管道及高压给水管道四大管道(以下简称"四管")是否采用弯管的问题,介绍了主蒸汽、低温再热蒸汽、高温再热蒸汽管道的规格和材质,定量分析了弯管、弯头阻力,比较采用弯管或弯头对电厂初投资、运行费用、管系应力等方面的影响。最后得出结论:弯管对热膨胀的补偿性差于弯头,不利于管系安全,增加管系设计困难,影响配合。提出"四管"全部采用弯头的建议。

Discussion on Selection of Bend or Elbow in Four Critical Pipes of Ultra Supercritical Unit

A study is made on whether to adopt bend or elbow for main steam pipe, low-temperature reheat steam pipe, high-temperature reheat steam pipe and high-pressure feedwater pipe （hereinafter referred to as four critical pipes） of 1 000 MW ultra supercritical unit. The specification and material of main steam, low-temperature reheat steam and high- temperature reheat steam pipes are described. Quantitative analysis is made of bend and elbow resistance. The influences of adoption of bend or elbow on initial investment, operation cost and piping stress of power plant are also compared. It is concluded that the compensability of bend to thermal expansion is inferior to that of elbow, which is not conducive to the safety of piping, increases the difficulty of piping design and impacts coordination. The use of elbow is suggested for all the four critical pipes.