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Gas appliance flame protection methods
To security needs, gas flame protection device is required, the relevant national standards which are also mandatory. At present the commonly used flame protection in three ways: Thermal, Thermoelectric and Photoelectric.
Thermal: also known as double metal piece. Double metal film is composed of two different expansion coefficient of metal formed together, under the effect of temperature, expansion coefficient of the metal side to the expansion coefficient of the metal side bending, when the loss of temperature, the original has been expanded metal bending will gradually return to their original state, so the two metal sheets, also known as shape memory alloy. The double metal sensor for safety protection device is using the bimetal effect of expansion in the temperature characteristics of bending.
Double metal protection device has the advantage of simple structure and low cost. Drawback is that installation difficulties, the installation of double metal location and plug valves and gas valve with a very high demand, and the large thermal inertia, open valve and closed valve for longer periods, short life.
Thermoelectric: This device is using the heat generated by gas combustion. Thermoelectric flame failure safety device by the thermocouple and the electromagnetic valve is composed of two parts, the thermocouple is composed of two different alloy combinations. Different alloy under the effect of temperature will produce different thermoelectric power, thermocouple is the use of different alloys under the effect of temperature produced by different manufacturers made thermoelectric power, which uses a different alloy materials of electric difference.
Thermoelectric safety device of simple structure, easy installation, low cost, has been widely used. However, such protection to the thermocouple as a heat sensor, thermal inertia big drawback is that the reaction is slow, people are not convenient operation, and short service life, plug and install the solenoid valve with high precision.
Photoelectric: also known as ion sensing. The device is the use of gas in the combustion flame and has a one-way with the ion conductive properties. This security method is applied to the first gas water heater, and from an early sense of DC to present the development of AC induction, so that reliability has been greatly improved, application of the stove still only three or four years old.
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