Filter Cloth is used in filters and strainers for the removal of foreign solids from a stream of liquid or gaseous fluid.
A strainer is usually a protective device to remove unwanted solids from a fluid such as fuel.
A filter is usually more complex and more of a precision instrument, to clarify a fluid or to remove particles larger than a certain critical size that are known to be present. Specific requirements of flow rate, pressure drop, and retention must be met.
Retention is expressed as the diameter of the largest solid spherical particle that will normally pass through a filter medium, usually expressed in microns. The data are necessarily approximate and will vary for different process conditions.