Filter cartridges are commonly used to process and remove sediment particles from liquids. When liquid travels through pipes, machinery, and other containers, it can pick up and transport various unwanted particles into its desired location. These sediment particles are not only bothersome but can be dangerous if found in certain liquids like drinking water or other beverages. Determining the correct filter cartridge type for a liquid helps to ensure that the sediment suspended in that liquid will be correctly and completely filtered out before the liquid reaches its final destination. By and large, filter cartridges are rated using micron size. This refers to the size of particle the filter will remove from the liquid being processed.
Variations of Filter Cartridges
There are a few different types of filter cartridges, including surface filter, depth filter, string wound, and high temperature filters.
Surface Filter Cartridges
Surface filters are meant to perform using only the surface membrane of the filter. To create a surface filter, sheets of various filtration materials (nylon, Teflon, polypropylene, etc.) are pleated and bonded at the ends, creating a greater surface area for liquid filtration to take place and therefore extending cartridge life. Contaminant materials are then caught on the surface of the filtration material, creating a layer that helps further aid in filtration.
Surface filter cartridges are also known as pleated filters and are designed to be used as pre-filters for coarser materials typically ranging from 30-500 microns. They are also able to be used in sub-micron applications, as their definable structure and pore size allows for consistent fine filtration.
There are a number of different advantages presented by using a surface filter cartridge. One big draw for pleated filters is their ability to be reused after being removed from the filter housing and washed off. Another advantage of surface filter cartridges is their customizable range of sizes. Pleated filters are generally used in semiconductor or pharmaceutical water filtration applications, as they possess a filtration rating of anywhere from 50-micron down to 0.04 micron absolute.
Depth Filter Cartridge
A significant advancement in filtration, depth filter cartridges, also known as melt blown cartridges are most commonly used in sediment applications. Made using polypropylene, melt blown cartridges will not transfer taste or odor onto the liquid being filtered. Depth filter cartridges are meant to remove rust, dirt, and other sediment from liquid. Melt blown filters have more porous outer layers meant to catch larger particles as well as inner layers made of a finer micron size, capturing smaller particles.
It is advised that melt blown cartridges are replaced on an annual basis. When compared to a surface filter or pleated filter cartridge, depth filter cartridges are able to remove more sediment from liquids and hold more sediment without sacrificing pressure or becoming clogged. Because of the porous nature of the filter, materials and particles removed from the liquid being filtered remain in the filter itself, as opposed to on the surface like pleated filters. This characteristic makes backwashing advisable when it comes to using depth filters. Backwashing involves inverting the flow of the liquid being filtered, helping to remove filtered solids which can cause resistance to filtration over time. For more information on depth filter cartridges, go here.
String Wound Filters
Considered especially advantageous when it comes to surface water filtration, string wound filters are a style of cartridge that has been around for a long time. In fact, string wound cartridges are known as the original cartridge. While this type of filter has been on the market the longest, it has certainly continued to prove its usefulness even today. Wound cartridges are designed to have a wire-type material that is wound up tightly around a core located in the center of the cartridge. The string that the cartridge is wound with varies in thickness by layer, which helps catch particles of various sizes within the filter. This allows the filter to be able to trap particles of a number of different sizes as well as the particles of its designated micron size without the danger of clogging. String wound cartridges are approved for use with temperatures of up to 125 degrees Fahrenheit. Their polypropylene construction also assists the cartridges in being chemical resistant. String wound cartridges also ensure no binders, lubricants, or additives leach into the water. These types of cartridges are meant to be replaced on an annual basis.
High Temperature Filter
High temperature filters are a specialized type of string wound filter. The difference between high temperature filters and typical string wound filters lies in the core of the cartridge itself. High temperature filters are made using stainless steel tubes in the center. These tubes are approved for temperatures up to 180 degrees Fahrenheit. As the name suggests, these types of filters are typically used in systems where the liquid being processed is at a higher temperature than normal string wound filters can withstand. High temperature filters are used in both commercial and industrial applications and are sometimes used in houses as filters on water heaters. Filters of this nature are commonly made of polypropylene, which makes them chemical resistant. High temperature filters have no additives, binders, or lubricants to leach into the water. It is typically recommended to replace these types of filters annually.
Which Liquid Filter is Best?
When it comes to what filter type is best, generally pleated filters are recommended as pre-filters of 30 to 50 microns. However, for fine sediment of around 1 to 5 microns, dual grade depth filters are recommended. Dual grade depth filters are designed to start filtering at 50 microns on the surface of the filter then filter down to 5 microns at the core of the filter. Dual grade depth filters are able to eliminate 2.3 times more sediment than typical wound string filters. However, it is important to remember that the question of which type of filter cartridge is best for sediment removal is not always so simple an answer. When it comes to choosing the correct filter, it is important to keep the project you are completing in mind, as the type of filter needed will vary depending on the characteristics required.