Tag Archives: Industrial Cartridge Filter

Read through our collection of articles on industrial cartridge filters.

The Importance of Measuring Pressure Drop

One of Filtra-Systems’ objectives is to help other companies improve their operational processes by efficiently filtering industrial water. Two solutions we offer our customers, bag filters and cartridge filters, are used in a wide range of industrial processes by companies in varying industries. Even though these filtering solutions are ubiquitous throughout industry, too many organizations neglect or improperly maintain them.

The Negative Effects of Poor Maintenance

Poor maintenance of filtering systems has a measurable adverse effect on business. One of the most overlooked aspects of proper upkeep is tracking the pressure drop across the filter housing. Both bag and cartridge filters are usually sized so that the pressure drop with clean elements is less than 1 psi. As the filter media collects dirt, sediment, and other contaminants, the pores in the media become clogged. The initial result of this is a less efficient system due to the clogged media’s restricted flow and increased pressure drop across the media. The differential pressure increases as more and more material is collected.

If left unchecked, the elements have the potential to rip, leading to a failure in filtering incoming fluid. Not only will no filtration occur, but previously captured contaminants will also be released. The failure of an operation’s filtration system can cause the entire operation to come to a halt, something every business wants to aviod. This can of course lead to missed deadlines and disappointed customers. Such negative effects are entirely avoidable if the proper measurement of pressure drop is observed.

How to Measure Pressure Drop

To prevent bags and cartridges from failing, the differential pressure across the filters should be tracked. This can be done by either using two pressure gauges (one upstream of media, one downstream), or a single differential pressure gauge. A typical bag will need to be replaced when the pressure drop reaches 10-12 psi, and most cartridges need to be changed when the pressure drop reaches 15-35 psi. Following these simple rules ensures that both bag and cartridge filters will continue to operate correctly.

Three Benefits of Wastewater Filtration

Wastewater filtration is a prudent practice for industrial companies, as it eliminates contaminants and other harmful substances from water and allows for proper disposal of those contaminants. In addition to the savings from water costs, it also has environmental implications, including reducing pollutant emissions. This reduction of pollution protects water supplies and other natural resources. Industrial plants across the country can benefit from flexible wastewater filtration solutions to make their commercial maintenance more efficient, and the following benefits are a direct result of applying an effective wastewater treatment solution.

Save On Expenses

In the past, companies could simply dump their waste into the nearest body of water.  Times have changed, and in many cases today simply disposing of untreated wastewater either into a water source or down the drain will incur heavy fines. By utilizing wastewater treatment solutions, this water can be reused, reducing your average expenses and transforming your wastewater into a money-saving asset instead of a burden. Also, fully automated solutions, like our STiR filter, reduce labor and decrease disposal costs to increase your bottom line.

Environmental Factors

Environmentally concious wastewater systems ensure that your company remains compliant with all relevant pollution laws, and does not harm the environment. By repurposing tainted water and turning it into something of value to your company, you remove the need for long distance transport and other wasted actions. Instead, you convert wastewater into a useful resource. These wastewater treatment systems also reduce your water consumption and discharge and produce minimal emissions compared to other systems.

Flexible Systems

Wastewater filtration provides flexible systems for water purification. As burgeoning technologies become available, you can integrate new solutions into your wastewater treatment systems to improve efficiency. Wastewater filtration is a scalable resource for commercial applications, which maximizes cost savings and maintains environmental compliance over time.

For more information on integrating a wastewater filtration system into your commercial business, contact us today, and stay tuned to our blog for in-depth articles on industrial filtration solutions.

Types of Industrial Water Treatment Equipment

Industrial water treatment equipment comes in a variety of implementations, all designed to suit particular operating needs. Filter presses, bed filters, cartridge filters and bag filters all excel in their intended applications. We’ll look at each type of filter and examine what applications it is most appropriate for below.

Filter Presses

Where most industrial water treatment equipment is designed to remove solid material from water, filter presses are designed to remove water from the solids. Filter presses are ideal for any filtration application where enough material needs to be removed so that more conventional filtration methods would be ineffective. A filter press operates, as the name implies, by exerting physical pressure usually in the form of either air or a water-filled diaphragm on a slurry mixture and extracting the moisture. The remaining cake of material is then disposed of.

Bed Filters

Bed Filters are filters with a bed of material (typically crushed walnut shell, sand, anthracite or activated carbon) that removes contaminants. Material is collected throughout the depth of the bed, allowing large amounts of material to be collected before a backwash cycle is initiated. Inlet water pumps through the filtration medium, which collects and suspends contaminants. Once the medium is saturated with contaminants, a backwash cycle is initiated. The filtration medium is fluidized and washed. This industrial water filtration method cleans the medium and readies the filter for use. This reuse of the filtration medium minimizes waste associated with the process.

Cartridge Filters

Cartridge filters are disposable, replaceable, self-contained filtration units. They consist of a central perforated core wrapped in layers of filtration material. Inlet water is pumped in through the top of the filter core, and passes through the walls of the filter. Contaminants can be caught throught the depth of the filter cartrige, which allows individual cartridges to achieve very high filtration efficiencies. Cartridge filters are typically used where high purity water is required.

Bag Filters

Bag filters are similar to cartridge filters in that they are also disposable and replaceable. Bag filters are shaped like a large sock, and are sometimes called sock filters or filter pots. They catch contaminants on the surface of the bag, and are typically used as a low cost option to remove particulate from wastewater streams.

How Industrial Water Filters Work

Industrial water filter design centers around separating contaminants, either solid or liquid, from a process fluid.  There are generally two types of industrial water filters designed for this use: surface filters, which consist of a single layer of filter material and rely on physically straining the fluid to extract contaminants, and depth filters, which are designed to use a porous filtration medium to collect contaminants throughout the medium, rather than just on the surface.  Depth filters are used predominantly in industrial water treatment because they allow the filter to retain a higher volume of contaminants before becoming clogged. This is due to the substantially higher available collection area (since contaminants are being collected throughout the depth of the medium, rather than merely on the surface layer of the filter).

Depth filters used in industrial water filtration typically use one of two types of filtration systems: filters with a bed of media, or cartridge filters.  While both of these systems perform similar activities, they differ in their effectiveness and optimal use.  Both types of filtration systems rely on fluid being forced through the filtration medium, either by pumping or using gravity to drain through.

Fluid is driven through the filter medium following constricted, tortuous routes, and the contaminants are caught, either due to direct collision with the filtration medium or precipitated by molecular attractive forces.  The selection of the type of filter media to remove contaminants is dependant on removal goals, as well as the type of contaminant.

Deep Bed Filters

Many different types of material are used in filter beds.  Sand filters are typically used in municipal treatment plants, walnut shell filters where oil removal is needed, and activated carbon for removal of heavy metals and other contaminants.  Over time, once the filter becomes restricted with captured particulates, a backwash of the bed is initiated.  Flow is redirected so that the downstream equipment is not contaminated, and the filtering layers are mechanically agitated.  Water is circulated through the filter during the agitation process to collect contaminants and, once the process is complete, exits through the backwash screen.  This screen allows the waste to pass through while retaining all of the filter media.  The wastewater is then sent to either upstream processing equipment or waste handling, and the filter is again ready for use.

Deep bed filters are used to filter drinking water, polish wastewater or cooling water, and as pretreatment for water desalination.  They are particularly effective as a means of removing solid particulates while minmizing maintenance.  The ability to backwash deep bed filters eliminates the need to replace filter media.  If activated carbon is used as a filtration medium, the filtration process will also remove tastes and smells from the filtered water.

Cartridge Filters

Cartridge filters for industrial water treatment systems usually consist of a single piece of filter material wound around a perforated cylinder, which is made of metal or plastic.  The unfiltered fluid enters the filter and is forced through the medium.  Once the filtration medium has reached its maximum contaminant load, it is discarded.  Cartridge filters are a low cost alternative to bed filters, that can achieve very high contaminant removal efficiencies at a fraction of the cost.

A Guide To Different Types Of Industrial Cartridge Filters

With the vast array of industrial cartridge filters available on the market today, it can be difficult for an engineer to figure out what shape, size, and type is right for his or her specific filtration need.  The fact that most cartridges have complicated, jargon-filled names like “2.5 DOE” and “Type 226 Option G” can add another layer of confusion to the decision making process.  In a continual effort to educate our customers and provide them with information that is applicable to their responsibilities, we have created this guide to clarify cartridge filter terminology and hopefully simplify your business’ ordering and re-ordering process.

DOE vs. SOE Cartridge Filters

One of the most common and simple classifications of cartridge filters is as either DOE or SOE.  They both have their own advantages and disadvantages:

  • DOE – The most common filter cartridges found are DOE, or Double Open Ended.  These cartridges have no built in seals on either end, thus the name.  Instead the filter cartridge housing is relied upon to seal one side and stop contaminants from bypassing the cartridge.
  • SOE – As the name indicates, Single Open Ended cartridges have one end sealed.  This seal is usually accomplished by using a polyporpylene cap.  By using a cap on one end, filter bypass is impossible, so systems that require higher purity filtration typically implement this type of cartridge filter.  The higher cost associated with the end cap prevents this type from being used in general applications.

Cartridge Filter Naming Terminology

In addition to the SOE and DOE divisions, industrial cartridge filters can be named by type, function, or after a component of the filter.

  • Type 222 – This type of filter is almost always SOE, utilizing a cap on one end.  They contain double gaskets that seal against the cartridge filter housing to provide better bypass protection than a typical DOE cartridge.
  • Type 226 – Also known as sanitary cartridge filters, Type 226’s have double gaskets which are similar to the Type 222.  Locking fins are included with this type of cartridge, which ensure proper installation of the filter.  When installing this type of cartridge into the sanitary cartridge filter housing, it must be properly lined up with the opening and twisted as it is pushed in.  This ensures a full lock and proper bypass protection.
  • Flat End – Typically used with DOE and Type 222 compatible cartridge filter housings, flat end cartridges are SOE with a flat plastic cap used for the seal.
  • Spear – An SOE cartridge with a pointed cap instead of a flat one.  It utilizes a bracket to eliminate the ability of the cartridge to sway, allowing it to maintain a seal.  Type 226 cartridges may also have this end configuration.
  • High Flow Cartridges – Designed for high flow rates, these cartridges have a much larger surface area than standard cartridges.  Most are 6.5″ diameter by 40″ long with a maximum flow rate of 350 gpm, whereas standard 2.5″ diameter by 10″ long cartridges have a maximum flow rate of 5 gpm.

Advantages Of Walnut Shell Media

Walnut Shell Media Filter has a variety of advantages over other options in industrial filtration, especially when filtering oil and total suspended solids (TSS).

Because our system  is a backwashing filter, Walnut Shell Filters not only are much better filters, but are more efficient in many processes because:

  • Hydrocyclones are often used for removing oil from water, but will not fully polish the water.  For example, oil droplets smaller than 20 micron are typically not removed by hydrocyclones.
  • Cartridges and bags are also frequently used but must be disposed of.  Maintenance personnel are also required to change the filter media when it becomes plugged.  Increasing restrictions on disposal in certain industries have also led to skyrocketing disposal costs.

How Backwashing Filters Work For You

When compared to hydrocyclones and disposable media filters, backwashing deep bed filters have these distinct advantages:

  • Contaminants are captured by a granular media bed and then removed by an efficient tortuous path through the media bed.
  • After the bed becomes full of contaminants, it is then backwashed, which cleans the bed without incurring media disposal costs.
  • For the filter to operate at a high efficiency over a long period of time, all contaminants from the bed must be removed during the backwash.

Better Filtration

One huge advantage of walnut shell media is its superior filtration of wastewater.

For example, Walnut Shell Filters will typically remove 95% of solids at 5 micron, and 90% of suspended oil.

Walnut shells have a natural affinity for oil, causing it to bond to the surface of the media.  Unlike in sand filters, whose captured oil films over the surface, captured oil remains as droplets.  These absorbed droplets will then contact smaller droplets, which coalesce onto the larger droplets and increase the removal rate of small particles over time.

That’s why black walnut shells have an oil absorption capacity that is 2-3 times that of sand.

Improved Efficiency

One of Filtra-Systems’ goals is to provide industrial filtration solutions that can improve a company’s operations in multiple domains.  Systems that require less maintenance not only help reduce upkeep costs, they also help to ensure that needless interruptions of operations that can have a negative impact on your company’s bottom line do not occur.

That’s why our Walnut Shell Filters media beds don’t require replacement for the entirety of the product’s life.  Because walnut shells are preferentially wetted by water, oil is easily rinsed from the shells during a backwash.

Black walnut shells (as opposed to English) have a high modulus of elasticity, which explains why the beds won’t need to be replaced.  The expected yearly attrition rate is only about 2%, which is much lower than English walnut shells, pecan shells, and other types of media.

And better yet, these filtering systems need less floor space to operate, freeing up room for other machinery.

By the way, walnut shell filters are typically sized at 10-12 gpm/ft2, which is a greater flux than competing media filters.  The higher flux means smaller filter housings can be used, which translates to more floor space.

The fact is, less water required to regenerate the bed is another benefit you’ll enjoy.  The flux required for fluidization of the bed is only 4.5 gpm/ft2 (based on a clean media bed, oil and solid saturation will increase this requirement), which is significantly lower than competing technologies.

Known Frustrations Of Sand Filters

To those who have had the misfortune of operating a sand filter, no explanation is needed for the common term “mudball.”

To the uninitiated, mudballs form when sand filters are exposed to oil that results in an oil film across the sand.  This film prematurely clogs the filter, drastically reducing the system’s efficiency.  The plugged bed has a decreased filtration area, and will backwash more frequently.

Unfortunatly, even after backwashing, the bed remains unclean because the backwash water does not penetrate the film and channels around the mudballs.

As the problem persists the bed will inevitably need to be replaced, a manual operation that requires your personnel to hand dig out the clogged bed.  This adds to unnecessary costs, both in paying trained personnel and expensive system downtime.

Is pricey filter replacement and disposal costing you a time and money? 

Generally, sand filter beds need to be replaced every five years.  However, with regular exposure to oil, replacement time can be reduced to as frequently as every six months.

An alternative to filter replacement is to clean the filter bed, a procedure that involves soaking the bed with a condensate, or a light oil.  The time-consuming nature of this process means that sand filter users typically choose to replace the bed instead.

Sand is also an OSHA dusting hazard and handling sand to replace the bed can result in exposure to plant personnel.

Sand filters typically use an air scour to remove oil and solids from the media bed.  Drawbacks to this technology include:

  • Incomplete fluidization of the media bed
  • Extra piping and valves required upon installation
  • Larger compressor and air regulator are needed
  • Possible installation of a vapor recovery and processing unit (VRU)

The compressed gas needed for this operation may also change the electrical classification of the area to Class 1, Div 1, increasing electrical costs for all process equipment nearby.

The backwash volume required for sand filters can be up to 5 times more than walnut shell filters.  

Sand filters are designed at 6 gpm/ft2, and the flux required for fluidization of the bed is 12 gpm/ft2 (based on a clean media bed, oil and solid saturation will increase this requirement).

Known Concerns Of Anthracite

Another common media filter is anthracite.  Anthracite filters usually have three layers of differently sized media: a top layer collects coarse contaminants, the second layer collects smaller particulate, and the third layer is the final polish.

Unfortunately, substantially more water is needed to clean anthracite filters.  Why?Because the backwashing process requires a subsurface wash to break up any waste before the standard backwash.  In fact, an anthracite filter may require seven times more water to backwash than a comparable walnut shell filter!

Additionally, upset conditions can cause the media to mudball.  The attrition rate for anthracite is much higher than walnut shells, and the media generally needs to be replaced every year.  Anthracite filters are designed with a flux of 4-4.5 gpm/ft2.

Filtration Design Flux

Backwash Fluidization Flux

Backwash Volume (compared to WSF)

Walnut Shell Filter

12 gpm/sqft

4.5 gpm/sqft


Sand Filter

6 gpm/sqft

12 gpm/sqft


Anthracite Filter

4 gpm/sqft



How To Avoid Problems When Changing Filter Cartridges

Although Filtra-Systems is known for designing and manufacturing great industrial filtration systems, we have also earned our reputation by providing excellent customer support to our clients around the world.  In addition to standard field service and replacement parts, we believe that educating our customers on product maintenance and best practices ensures that our customers are getting the most out of our systems for their business’ needs.

Minimizing potential issues for our customers is what we hope to achieve with this 8-step guide on how to properly replace cartridge filters.  Proper replacement of these cartridges reduces the risk of future problems occurring and maximizes floor cleanliness.

Our 8-step guide:

  1. Isolate the filter housing.  Closing valves on both the inlet and the outlet will ensure that fluid is not introduced into the housing while it is open.  Back pressure from the system may cause fluid to flow back into the housing, so it is important to close the outlet isolation valve as well.
  2. Open the vent valve.  Venting the housing will allow excess pressure to bleed off, eliminating dangers when opening the housing.  It will also prevent the housing from air locking when attempting to drain it.  The vent should be plumbed to an upstream tank, to minimize operator exposure to process fluids.
  3. Open the drain valve.  The housing must be drained before the cartridges can be accessed.  Drain the fluid from the housing, and reintroduce it to the system upstream of the filter.  A process should be developed that will ensure maximum plant cleanliness.
  4. Open and remove the lid.  Remove the top plate so that the cartridges may be accessed.
  5. Remove cartridges, and discard.
  6. Install new cartridges.  If Type 226 cartridges are used, remember to twist the cartridge into the base of the housing, so that they lock.  Re-install the top plate, and tighten so that there can be no fluid bypass of the cartridges.
  7. Check the vessel gasket for defects, and make sure that it is in the proper position.  Replace the lid.
  8. When refilling the housing, make sure that the drain is closed, and vent is open.  Open the inlet, and leave the outlet closed.  Venting the housing while refilling it will prevent air from being trapped in the housing.  When the housing is full, and no air bleeds through the vent, close the vent and open the outlet.  The housing is now back online.

Filtra-Systems cartridge housings are designed to be simple to use and safe.  Following these easy steps will eliminate spillage, and will ensure that leakage does not occur while the filter is in operation.  To see our full line of cartridge housings, click here: http://www.filtrasystems.com/industries/bag-and-cartridge-filter-products/