Question 478Steam Plants - Assistant Engineer

The correct answer is A) before reducing the forced draft pressure. To safely decrease the boiler firing rate, you should always reduce the fuel pressure before reducing the forced draft pressure. This is because reducing the forced draft pressure before reducing the fuel pressure can lead to an imbalance in the air-fuel ratio, which can cause incomplete combustion and potentially dangerous conditions in the boiler. By first reducing the fuel pressure, you can ensure a proper air-fuel ratio is maintained, allowing for a safe and controlled decrease in the boiler firing rate. The other options are incorrect because C) opening the oil recirculating valve and D) opening the fuel pump relief valve do not directly address the need to reduce the fuel pressure before the forced draft pressure.