Technically speaking, static pressure is defined as the pressure of a fluid on a body when the body is at rest relative to the fluid. A simpler way to think of it is as the resistance created by a dust collection system and its associated duct work. In the dust collector world, static pressure is generally measured in inches of water in a water gauge.
What causes static pressure in a dust collector?
There are a variety of things that cause static pressure in a dust collection system. Clean or dirty filters cause static pressure. Any elbow in a duct run will cause static pressure. Passing air through a tube sheet of a dust collector will cause static pressure. Air entering into a duct system will cause static pressure.
Why is this important?
It is important to know the total amount of static pressure on a dust collection system so that we can chose the right fan to supply the right amount of CFM. If the fan supplied with a dust collector cannot handle the static pressure, it will not perform properly and the dust collector will not do its job.