When taking a shell-and-tube heat exchanger with a removable tube bundle such as a bayonet-tube heavy fuel oil service heater out of service, to prevent water hammer what statement represents the correct operating procedure?
• Water hammer causes and how sudden steam or condensate changes create pressure shocks • Proper sequence of securing a steam heater: steam, condensate, and process fluid (fuel oil) relationships • Role of condensate drains in removing condensate and preventing live steam from discharging directly to drain
• Think about what happens inside the heater if you shut off the fuel oil first while steam is still on and condensate is forming. • Consider whether you want condensate or live steam coming out of the drain lines as you secure the heater and which condition is safer for the system and piping. • Ask yourself: in what order should steam, condensate drains, and fuel oil be handled so that the shell does not trap condensate with live steam above it?
• Verify which step mentions opening or cracking condensate drains first before changing steam flow. • Check which choice avoids having live steam blowing to the drain for an extended time, and instead drains primarily condensate. • Confirm that the fuel oil flow is not secured so early that the heater stays hot with steam but no flow, encouraging condensate accumulation and potential water hammer.
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