In the steam turbine for combined cycle power generation operated for a long time, thermal and mechanical deformation is accumulated in the High-Intermediate Pressure (HIP) casing due to repeated start-up and stop under high temperature and high pressure conditions. This study attempted to quantitatively evaluate the deformation characteristics based on the measured data and analyze the effect of casing deformation on casing alignment and inner gap. To this end, the level of the horizontal split flange surface was precisely measured and analyzed for the two decomposed steam turbine high-pressure casing of the combined thermal power plants. As a result, Hogging deformation occurred throughout the casing, and a maximum strain deviation of 0.83 mm between the upper and lower casings was confirmed, and an asymmetric deformation tendency was confirmed in which the upper part was more than twice as large as the lower part. Based on this phenomenon, by estimating the amount of centerline movement and the change in the inner gap that can occur during assembly due to the upper and lower deviation of the casing Hogging deformation, it was confirmed that Hogging deformation is a major influencing factor on casing alignment.

Abstract
1. 서 론
2. 연구 방법 및 실측
    2.1 대상 설비
    2.2 내부 간극의 의미
    2.3 케이싱 변형상태 측정
    2.4 자료 분석(Data Processing)
3. 케이싱 변형 특성
    3.1 Hogging 현상
    3.2 비대칭 변형
    3.3 케이싱 변형 경향(Spatial Distribution)
4. 조립 후 내부간극 변화 예측
    4.1 케이싱 내부간극 기준치
    4.2 조립 후 변화
    4.3 다양한 내부간극 변화 요인
    4.4 Hogging에 의한 내부 간극 변화와 영향
5. 결 론
후 기
References

• 남궁장(Korea Institute of Power HRD, Instructor) | Jang Namgung
• 최승근(KEPCO KPS, Turbine Engineer) | Seungkeun Choi
• 조대환(Mokpo National Maritime University, Professor, Thermofluid Dept.) | Daehwan Cho Corresponding author