Steam pipe washing method for 1000MW ultra-supercritial double reheat boiler

The invention discloses a steam pipe washing method for a 1000MW ultra-supercritial double reheat boiler. The steam pipe washing method adopts a mode assisting two-stage heat storage pressure reducing pipe washing with pressure stabilizing pipe washing. Pressure reducing pipe washing can disturb impurities, such as oxide skin, on a heated surface and in a pipeline through continuous work condition variation so as to peel the impurities off the heated surface and discharge the impurities out with pipe washing steam current. Pressure stabilizing pipe washing can carry particles on the heated surface and in the pipeline through long term of large momentum ratio coefficient. A first-stage single washing superheater adopts pressure reducing pipe washing until a target board is examined qualified. In view of reheater small resistance and large pipe washing coefficient, the pipes of a primary reheater and a secondary reheater are no longer washed separately, a second-stage superheater, the primary reheater and the secondary reheater are connected in series, a particle collector is additionally arranged on an inlet of the secondary reheater, pressure stabilizing pipe washing and pressure reducing pipe washing are carried out in a crossed manner, pressure stabilizing pipe washing is followed by pressure reducing pipe washing, the particle collector is cleared in the boiler stop cooling period, and pressure stabilizing pipe washing and pressure reducing pipe washing are simultaneously carried out until the target board is examined qualified.