| 摘要 |
PURPOSE:To control a thermal stress generated in a bypass valve casing at the time of the bypass valve testing by an arrangement in which the valve is temporarily held stationary after it is slightly opened, and once the differential temperature between the inner and outer wall metals of the bypass valve casing became within the tolerance, the valve opening is enlarged. CONSTITUTION:At the time of valve testing, feeding a valve test start signal 13 into a control device 12 will cause a valve test signal 17 to be sent from a valve test signal generator 25 to a valve actuating section 11, and a bypass valve 8 starts opening. When its opening reaches to the set value, the valve test signal 17 is terminated by a valve opening signal 16. Under such conditions, the inner wall of the bypass valve casing is gradually heated by a very small amount of steam through the valve 8, and the temperature of the outer wall is also risen. If the temperature signal 14 of said inner wall metal is higher than a specified value 19 and if the difference between inner and outer wall metal temperature signals 14, 15 determined by a comparison device 22 is within a specified value 23, a signal is outputted from an AND circuit 24 so that the valve test signal 17 may be again delivered to open the bypass valve 8. |
