Insufficient output and rising pressure after governing stage of a 630 MW supercritical unit occurred only 18 month after the first outage. Though analysis based on measured parameters, fouling existed in governing stage and the first stage group. By virtue of linearization of formula and decoupling the impacts to thermal characteristic parameters, the quantified deposition degree was obtained. The fouling reason was determined by scale sample analysis, and the solution was proposed by quantitative calculation. The problem was successfully solved with boiler pickling, turbine cascade jet-beading and pulsing minimum oxygen to inhibit flow accelerated corrosion. A steam quality detection method was also proposed as the installation of measurement point after governing stage of supercritical unit. These treatments provided building and operation experience for 1000MW ultra-supercritical turbine and the same type of equipments.

It is well known that the hydraulic drag force on objects cant be ignored in computing the movement of objects in water. And the drag forces on sphere and cuboids have long been studied. While in hydraulic engineering, objects with regular tetrahedron shape are widely used to form the foundation and temporary dam for they can interlock each other to obtain a compacted integral. In this article the vertical hydraulic drag force on regular tetrahedron is studied by indoor experiments, the relation of the vertical hydraulic drag coefficient and the vertical velocity is proposed. And the max vertical speeds of different materials are deduced. The result is helpful to compute the movement of regular tetrahedron in water and estimate the impact effect on the groundwork.