Bead dusting and breakupis a common cause of pressure drop increase. This is often caused by upsets such as rapid pressure swings, liquids carryover, regeneration refluxing, and flow channeling. Rapid pressure swings can cause movement of the sieve orthe entire bed in some cases. When severe enough it can lead to flow channeling in the bed and early breakthrough in addition to increased pressure drop. Liquids carryover eventsin which liquids slam into the bed can cause sieve breakup, especially for repeated occurrence when it is a chronic problem. Regeneration refluxing occurs when liquids rain down on the sieve bed due to cooling and condensing at the top of the vessel early in the heating cycle while simultaneouslyliquids are being vaporized and driven from the sieve bed.It creates a rolling boil that can breakdown the sieve over time. In general, even under the best of circumstances, the pressure drop across the sieve bed normally goes up by 1.5-2 times over the life of the sieve due to bed settling and compaction, coke and carbon buildup on the sieve, anddust and particulate matter that collects in the bed.