In downflow pattern, inlet nozzle is also used as manway for internals introduction and catalyst loading.
In this case, the connecting pipe is a smaller diameter featuring a 90° elbow and allowing its easy dismantling. Therefore, the incoming pipe is welded to a custom made reduction flange. The feed diffuser can be either attached to this flange or sitting in a groove between the flanges.
Depending upon flow dynamics of reactor top head and process operation, the feed diffuser is designed from a mix of plate, screen, and perforated plate.
Usually, an impingement plate faces the incoming flow which may be diverted through several channels. Its size depends upon the incoming pipe diameter and the nozzle height.
In upflow patterns, the feed diffuser is laying above the inlet nozzle.
It may be necessary to have a removable equipment that will allow easy cleaning of the parts