Question 469Steam Plants - Assistant Engineer
70% to passWhich of the following actions takes place in the control circuit of an automatically fired auxiliary boiler when the desired steam pressure is obtained?
AA temperature sensing device opens the circuit breaker in the burner motor.
BThe high limit control secures power to the entire oil firing system.
CThe stack relay actuates the low limit control which breaks the ignition circuit.
DThe stack relay secures power to the high voltage side of the ignition transformer.
AI Explanation
The correct answer is B) The high limit control secures power to the entire oil firing system. When the desired steam pressure is obtained in an automatically fired auxiliary boiler, the high limit control activates to secure power to the entire oil firing system. This prevents the boiler from generating more steam than the desired pressure, which could be dangerous. The other options are incorrect because they do not accurately describe the actions that take place in the control circuit under these conditions. A temperature sensing device does not open the circuit breaker, the low limit control does not break the ignition circuit, and the stack relay does not secure power to the ignition transformer.
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