Dispositif pour empêcher la surchauffe du serpentin d'une chaudière

984,117. Safety shut down systems. VAPOR CORPORATION. Aug. 8, 1963 [May 6, 1963], No. 31297/63. Heading F4B. [Also in Division G4] In tubulous water boiler, a thermocouple is attached to the outlet pipe and exposed to heat from a burner, and the output from the thermocouple is amplified and fed to an electronic trigger circuit to shut down the burner when the surface temperature of the pipe exceeds a predetermined limit. The thermocouple 18 is mounted on the outlet pipe 16 of coiled tube boiler 10 heated by a burner 15, and is mounted so that it is exposed to the combustion gases and radiation from the burner. The thermocouple comprises a constantan wire 21 surrounded by insulation within an iron sheath 23 which is welded into a dimple in the outlet pipe 16, Fig. 5, so that the sheath 23 is maintained at the temperature of the pipe 16. The junction of the thermocouple is located at a hot-spot within the boiler. In another form of thermocouple, Fig. 7, the pipe 16 forms one element of the thermocouple, and a protective cover 29 is welded over the constantan wire 26 and its insulation in a groove in the pipe 16. The output from the thermocouple, compared with a reference voltage, is fed to a magnetic amplifier, and to a transistor trigger circuit, Fig. 8 [not shown). The arrangement is such that, during normal operation, a relay is energized to close contacts in the burner control circuit and maintain contacts in an alarm circuit open. Overheating indicated by the thermocouple, or failure of any of the components of the control circuit de-energizes the relay to cut the burner off and sound an alarm.