What is
Interstitial Velocity?
Interstitial velocity is the speed at which air moves between the filter bags inside the baghouse. This is different from the main airflow—it refers to how air travels in the small spaces between filters.
INTERSTITIAL VELOCITY CALCULATOR
Importance of Interstitial Velocity in Baghouse Design
If too much air is pushed into too small a unit, bags are spaced too close together, the interstitial velocity might be too high because there is very little area between the bags for the gas stream to pass through. The settling of dust particles during bag cleaning would become difficult at high velocities. When pulsed, the dislodged dust might stay aloft for a time only to then get sucked right back onto the filters. One can often diagnose high internal velocities by observing when units have difficulty maintaining a stable differential pressure over time and continually removing dust from the hopper. If these issues quickly remedy themselves when the unit is cleaned offline, most often high interstitial velocities are to blame.
Note: Use this as a reference, but remember—bag spacing, dust loading, and air patterns also affect system performance. Get a full evaluation from a baghouse expert before making changes.