Question 361Steam Plants - Assistant Engineer

The correct answer is D) all of the above. The purpose of the boiler drum air cock is to serve all three functions - admit air when the boiler is being emptied (A), permit escape of air when the boiler is being filled (B), and permit escape of air when steam is forming in the drum after lighting off (C). The air cock allows the controlled release or admission of air during various stages of boiler operation to prevent pressure imbalances that could damage the boiler. This is a critical safety feature required by Coast Guard regulations for properly operating marine boilers.