The vent line from the main condenser water boxes was not opened when the waterside was recharged. This would __________. lead to a build up of pressure on the tube sheet of greater than 40 psig prevent the design vacuum from being attained under normal operating conditions at sea
• Function of condenser water box vent lines in a main condenser cooling system • Effect of air pockets on condenser vacuum and heat transfer • Difference between pressure on the tube sheet during filling vs. vacuum performance during operation
• Think about what happens inside the water box if it is refilled with the vent line shut. Where does the displaced air go? Does it compress, or does it stay trapped? • Consider how trapped air on the waterside would affect the condenser’s ability to remove heat and maintain vacuum at sea. • Ask yourself: during filling at low pressure, is it likely that the tube sheet will see pressures much higher than normal cooling-water pressure just because the vent is shut?
• Verify what venting a condenser water box is intended to prevent: overpressure, air binding, or difficulty achieving design vacuum. • Consider typical pressure limits on tube sheets and normal seawater cooling system pressures to judge if >40 psig from trapped air during filling is realistic. • Confirm how air entrapped on the cooling-water side influences the ability to reach design vacuum on the steam side of the condenser.
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