To prevent a valve body and a downstream pipe from vibrating effectively by suppressing unstable flow, shock wave and excess flow of steam and fostering valve seat attached flow by a skirt-shaped portion having an appropriate broadening angle.
A valve casing 5 includes a valve body 56 and a valve seat 58 having a curvature relationship of R=(0.52 to 0.6)D, r>0.6D where the curvature of the valve body 56 is R, the curvature of the valve seat 58 is r, and the bore diameter of the valve seat at a contact point P between the valve body 56 and the valve seat 58 is D, and an edge portion 56a is formed on an end surface on a curved portion on the lower end of the valve body 56, and a skirt-shaped portion extending toward a downstream pipe 3 is formed on the valve seat 58, with a broadening angle θ of the skirt-shaped portion being θ≤6°.
ASAKURA DAISUKE
YAMAMOTO TETSUZO
NARABAYASHI SUNAO
HOSAKA HIDEO
HOTOKEZAKA SHIGEKI
FUJIKI YASUNOBU
MURAKAMI MASATAKA
ASANUMA YUTAKA
MORI HARUTSUGU
TEZUKA KENICHI
TOSHIBA CORP
Shunguchi Sekiguchi