🔍 Key Concepts

• DC heater (direct-contact feedwater heater) function in a marine steam plant • Relationship between relief valve operation and pressure in the heater shell • Which inputs (condensate, recirculated feed, makeup feed, or auxiliary exhaust steam) most directly affect shell pressure

💭 Think About

• First, think about what a DC heater relief valve is protecting against: is it high level, high temperature, or high pressure? • Of the four choices, which flow or condition would most directly and quickly raise the pressure inside the heater shell to the point where a relief valve would lift? • Consider which streams usually enter the DC heater at or near saturation pressure and are used to heat the feedwater—how would a change in that source affect the relief valve?

✅ Before You Answer

• Verify which stream controls the heating steam pressure on the shell side of the DC heater. • Check whether increased water flows (condensate, recirculated feed, makeup) would tend to increase pressure, or mainly affect level and temperature instead. • Confirm your understanding that a relief valve is primarily a pressure safety device, not a level controller.