When taking a shell-and-tube heat exchanger with a removable tube bundle such as a bayonet-tube type heavy fuel oil service heater out of service, to avoid thermal shock what statement represents the correct operating procedure?
β’ Thermal shock in shell-and-tube heat exchangers (how rapid temperature changes affect metal parts) β’ Typical start-up and shutdown sequence for steam heaters handling viscous fluids like heavy fuel oil β’ Which side (steam or oil) normally provides the greater/quick temperature change to the tubes
β’ In a steam-to-heavy-fuel-oil heater, which fluid can change temperature and pressure more rapidly, and which is more viscous and slower to change? β’ If you suddenly remove the heating medium but leave a hot, viscous oil sitting in the tubes, what stresses or problems could occur? β’ During shutdown, which side should be adjusted gradually to avoid sudden temperature changes in the tube bundle?
β’ Identify which side (steam or heavy fuel oil) is the primary source of rapid temperature change and therefore the main cause of thermal shock if changed suddenly. β’ Check which procedure avoids trapping hot, viscous oil without proper heating, which can cause waxing/solidifying and mechanical stress. β’ Confirm that the correct choice involves a gradual change on the side that most strongly affects tube metal temperature, rather than an abrupt, simultaneous shutdown.
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