| 摘要 |
<p>1345021 Burner safety control circuit COMBUSTION ENG Inc 10 June 1971 [11 June 1970] 19992/71 Heading F4T A burner safety control circuit which distinguishes between transient power interruptions and emergency conditions comprises a safety shut off valve 34 across which is connected a time delay loop 36 whereby, in the case of a power interruption a trip delay unit 42 can maintain valve 34 energized (i.e. open) for a discrete period, e.g. of one second until a time delay switch 40 opens in delayed response to de-energization of its controlling relay 22 and a further switch 24 controlled by relay 22 maintains for the same discrete period a path for re-energization of relays 18 and 22 if the power interruption is only transient; in the event of emergency conditions such as flame failure or feedwater interruption however, a switch 14 responsive to boiler conditions opens to de-energize relay 18 which closes a switch 26 whereupon a relay 28 is energized and a second time delay switch 38 in loop 36 is opened after a discrete period much less than that of switch 40 (e.g. 0À1 second) to shut off valve 34. As well as switch 14 responsive to boiler conditions, a switch 30 may open if the emergency is in the burner system.</p> |
