Why is the tube cut before installing the second plug in a plugged exchanger tube?

• A. To prevent pressure build up
• B. To ensure a tight seal
• C. To prevent corrosion
• D. To fit more easily

Answer: (A)

Relief of trapped pressure during plugging is the key idea. When a second plug is installed in a live tube, any gas or liquid behind it would be compressed if there isn’t a way for that space to vent. Cutting the tube beforehand creates an opening for that trapped volume to escape as the plug is driven in, preventing pressure from building up between the plugs and reducing the risk of the plug being forced out or the tube being damaged. The plug’s job is to seal, but cutting isn’t about a tighter seal, corrosion prevention, or easier fitting—it's about avoiding dangerous pressure buildup during installation.