🔍 Key Concepts

• Boiler draining procedures and why venting/air cocks are used • Effect of vacuum formation inside a closed container as liquid drains • Purpose of preventing damage or distortion to boiler components during cooldown and draining

💭 Think About

• As water leaves an enclosed boiler, what happens to the pressure inside if no air can enter? • Which option focuses on pressure conditions inside the boiler rather than extra benefits like drying or cleaning? • When engineers talk about opening vents or air cocks on tanks or boilers, what problem are they usually trying to avoid?

✅ Before You Answer

• Identify which choice deals directly with preventing vacuum formation rather than side effects like drying or cleaning. • Check which option describes a normal safety practice in draining any large closed vessel, not just boilers. • Eliminate options that sound helpful but do not address the pressure balance inside the boiler.