In shell and tube heat exchangers, the fluid entering the shell side can create a high-velocity jet as it exits the inlet nozzle. If that flow is directed straight at the tube bundle, it can cause tube erosion, vibration, and localized mechanical damage over time. To prevent this, designers often include impingement protection at the shell inlet.

Impingement protection can take several forms, such as a plate, rods, or a vapor belt. The goal is to break up or redirect the incoming flow before it reaches the tube bundle. Some impingement designs limit the area available in the bundle for tubes. TEMA gives guidance on when impingement protection is required or should be considered, based on factors such as fluid density, velocity, and nozzle size. Although it may seem like a small detail, proper inlet protection can play a critical role in extending the life and reliability of a heat exchanger.