Abstract: Elliptical self-tight seal manhole with inside opening on steam drum is a common self-tight seal structure. However, there's no detailed description of the seal design of this structure in the existing standards and references, and there's a lack of instruction methods for reasonable gasket selection, and the problems of seal leakage and seal failure often occur in the practical application of engineering. In order to ensure the reliability of such seal from design calculations, the concept of gasket reliability factor was presented. According to structure analysis and summary of the application examples, this paper proposed four-step calculation method for the design of elliptical self-tight seal manhole with inside opening on steam drum including the formula to calculate and correct gasket effective sealing width and the formula to calculate the sealing performance.

Key words: elliptical manhole, calculation of self-tight seal, elliptical gasket, steam drum