The Difference Between Filters and Strainers

Filtering or straining can prevent unwanted particulates from fouling dispensers or fillers and affecting the consistency and flavor of a finished product.

Metaphorically, straining is a colander for spaghetti noodles, while filtering is the paper filter used for coffee grounds. These questions can determine whether filtering or straining would be a better fit:

1. What needs to be removed from the product?
2. How large are the particulates in question?

Filtering and straining differences

Filtering refers to a finer removal process. Filters usually employ some form of “sock” or cartridge that has the ability to remove small particles down to the size of fine sand, or even microbials.

Straining is generally considered a coarse operation and is employed to catch larger chunks (around 1/4 inch).

Mesh or micron are common measurement units that are analogous to each other. 35 mesh is roughly equivalent to 500 micron. In general, mesh will be used for straining and micron will be used for filtering.

By definition, a micron is a unit of measure equal to one millionth of a meter. Mesh (referring to square mesh) means the number of “squares” is the same in either direction. For example, three squares per inch is three mesh.

Vee-Wire® (Visually similar to Wedgewire)

Vee-Wire®, or Wedgewire, inserts are typically used in applications where robust design is required. The inserts offer more support for viscous products. A filter sock needs a support ring or mechanism to keep it in place, but a Vee-Wire screen will not usually need additional support inside the housing.

Choosing a Method

Consider these questions before deciding on a filter/strainer method:

1. What does the process dictate?
2. What is needed to get an operation up and running?
3. What process parameters need to be adhered to?
4. How important is it to get all of the particles out of the product?

Each different filter/strainer methods reduce the spacing allowed for product to move through. The process parameters should dictate a fairly clear path to an appropriate filter/strainer.

Additional considerations for finding the right filter/strainer might also include any restrictions you might have in positioning the filter/strainer. For instance, the Mainstream filter/strainer by Alfa Laval can only be positioned vertically, while the Alfa Laval's Streamline filter/strainer is an inline system that can be used in any position. Lastly, strainers should be considered when it comes to protecting your equipment and product. For instance, magnetic stainers can be also be used to prevent metals from contaminating your product or damaging your equipment.