During the installation process, most of 1000MW-class nuclear power steam turbines will undergo certain deformations due to their own big size and heavy weight, which will change seal clearances of steam passage. If the clearance is too big, it will lead leakage loss and affect steam turbine’s efficiency. If the clearance is too small, it may cause the rubbing fault between moving and static components and even the strong abnormal vibration, affecting the safety of steam turbines. Moreover, limited by the complex structure and measurement method, it is difficult to measure deformation and seal clearance accurately, so it’s necessary to study change tendency of the clearance in installation process.

In this paper, a High and Intermediate Pressure (HIP) casing of a 1000MW nuclear steam turbine was taken as the research object, and we firstly established its 3D geometry model based on Pro/E software. By using ANSYSY Workbench, a finite element (FE) model of HIP casing was established. Then we calculated the deformation of the lower half casing with the lower diaphragms and with both the lower and upper diaphragms respectively. Besides, considering the complexities of casing installation, the Multi-Load Step Method was used in numerically calculating. And to simulate continuous deformation of the casing installation process, five steps were adopted, named as: ① lower inner casing with lower diaphragms, ② step① + upper diaphragms, ③ step ②+ upper inner casing, ④ step③ + bolting, and ⑤ replacing the support. Deformations at many points on casing and diaphragms were calculated, and we analyzed the differences of deformation of these points under different conditions, which reflected the change of the seal clearance during the installation process. Finally we compared the clearance change with the operational monitoring data.

The calculation results show that the maximum deformation of the HIP Casing during the installation process occurs in the middle of casing close to the Intermediate Pressure (IP) end. The diaphragm clearance and the blade tip clearance will increase relatively when the upper diaphragm is fastened to the lower, and increase relatively when the upper half casing is fastened to the lower half, and decrease relatively when bolts are tightened, and then increase after the support is replaced. The relative change amount of the clearance during the whole process is 0.6-0.8 mm. The change of diaphragm clearance of the first-stage in IP end is the largest, and the rubbing fault may occur between the moving and static components during the support replacement process, if the installation clearance between diaphragms and rotor is less than 0.8mm.


Numerical Calculation of Seal Clearance Change in Installation Process of a 1000MW Nuclear Steam Turbine HIP Casing

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

Turbo Expo - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.