| 摘要 |
A ball valve is produced, which has a valve housing 10 and a ball 20. A pair of mirror-symmetrical housing halves 12, 14 are jointed together along a single weld line. The housing halves are jointed together by welding in a manner to enclose the ball previously provided with a through bore and a pair of recessed portions. The through bore 22 of the ball is arranged to be in conformity with the weld line. Holes 42, 50 for respectively mounting a pair of stem assemblies are formed by machining respectively in those portions of the valve housing opposed respectively to open opposite ends of the through bore. The centers of the holes are in alignment with the operational centerline of the ball valve. The ball is turned by an angle of 90 degrees, thereby bringing the through bore of the ball into alignment with openings 12A, 14A of the valve housing, and the recessed portions 26, 28 of the ball are brought into alignment with the holes, respectively. Next, the pair of stem assemblies 60, 68 are attached to the both holes, respectively, and stems are fitted in the both recessed portions, respectively, and the pair of stems are welded circumferentially to peripheral edge portions of the holes, respectively.
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