PURPOSE: To aim at reducing heat transmission performed through a contraction cylinder and protect a bearing and the like by providing sectional gaskets on the end face of the contraction cylinder.

CONSTITUTION: Sectional gaskets 32, 33 are provided on the casing side end face of a contraction cylinder 27 formed separately from a casing 21. A fitting part 31 for centering is provided at the connecting part between the casing 21 and the contraction cylinder 27, and a minimum contact part 34 necessary for centering and a heat transmission reducing escape groove provided occupying almost all of the remaining part are formed at the fitting part 31. As a result, the heat transmission between the casing 21 and the contraction cylinder 27 is reduced to the minimum by the sectional gasket 32 as well as the direct contact between the liquid in the casing 21 and the fitting boss 31b of the contraction cylinder 27 is avoided by the sectional gasket 33. Accordingly, the heat transmission into a bearing case 24 can be reduced, and a bearing 25 and a shaft sealing device 26 can be protected from thermal damage.