| 摘要 |
PURPOSE:To prevent a chimney from heat fatigue by comparing gas temperature at an outlet of a steam generator with a specified value to open a low pressure bypass valve for increasing temperature drop of exhaust gas when said gas temperature departs from the specified value. CONSTITUTION:In a combined cycle plant having high and low bypass systems, the above-mentioned steam pressure controlling apparatus is provided with high and low steam pressure controlling systems 20, 40 respectively for controlling high and low bypass valves 17, 18. In this case, the low steam pressure controlling system 40 is provided with a relay coil 44 energized by the output of a comparator 44 when gas temperature at an outlet of a steam generator detected by a temperature detector 41 exceeds a specified value set by a temperature setter 42. The energizing force of the relay coil 44 changes over a relay contact 44a to the control setter (pressure setter) 45 side the output of which is supplied to the input of a deflector 33. The low pressure bypass valve 18 is constituted to be operated in the open direction through an adjuster 34 by the output of the deflector 33. |
