| 摘要 |
PROBLEM TO BE SOLVED: To provide a boiler 1 capable of easily and rapidly detecting a valve-over leakage of a shutoff valve 14 for changing-over a presence or non-presence of gas supply for a burner 4 when the shutoff valve is closed, showing a superior load following characteristic while assuring its safety characteristic and reducing radiation loss as well.SOLUTION: A leakage detection means 16 determines presence or non-presence of a gas valve-over leakage exceeding a set flow rate during closed-state of a shutoff valve 14. While the burner 4 is stopped, when leakage exceeding the set flow rate is detected by the leakage detection means 16, operation transfer to an igniting operation is prohibited, and in turn when a leakage exceeding the set flow rate is not detected, an operation transfer to an igniting operation without any purge can be carried out if it is within a safe waiting time form completion of purging after closing of the shutoff valve 14. The safe waiting time is set within a time in which gas concentration within a furnace reaches an explosion lower limit concentration. Since the operation transfer to the igniting operation can be carried out without any pre-purge, it shows a superior load following characteristic and a heat radiation loss can also be reduced. |
