Custom Bag Filters: Types, Benefits & Applications

Every filtration job is not the same. There are different fluids, contaminants, housing sizes, temperatures, and chemistries across varying plants. While an off-the-shelf standard bag fits many common situations, numerous industrial processes do not fit the standard application.

Here custom filter bags come into the picture. These are filter bags manufactured to very precise specifications: a desired micron rating; a selected media; a precise size; a unique seam or seal ring, or a combination of these. The bag, instead of being forced to adapt to the process, fits the process.

This guide details what a custom bag filter is, the principles by which it operates, how it is implemented, and where to source a suitable filter. The objective is to guide you to determine if the use of a custom solution is justified.

What Are Custom Bag Filters and Why Industries Use Them

A custom bag filter is simply a liquid filter bag that is made to a specific dimension that cannot be fulfilled with a standard catalogue product. In essence, a bag filter simply traps solids as liquid flows through and allows clean liquid to move on. However, the micron rating, material, size, and design are all specific to one use.

Custom bag filters for industrial use are often considered when a standard bag simply is not good enough to prevent companies from losing money and/or quality, for a variety of common reasons including:

• The housing is an atypical size, and a standard bag simply will not create a good seal with it.
• The fluid chemistry and/or temperature dictate the use of specific media.
• Regulated process which requires traceable and compliant materials, plus prescribed packaging.

Read More: What Are Industrial Bag Filters and How Do They Work?

Common Problems in Industrial Filtration Without Custom Bag Filters

Running a process on an incorrectly sized bag will initially produce only minor problems, which will become expensive down the road.

• Running on an improperly sized bag allows unfiltered liquid to bypass the seal, leading to contaminants flowing into downstream equipment.
• Using a bag that is too coarse will allow contaminants through; using one that is too fine will quickly clog, leading to more bag changes and increased pressure drop.
• The incorrect material will break down if exposed to heat or strong chemicals and release fibres or break down prematurely.
• An ill-matched bag can be overfilled or become redundant quickly, increasing labour and material costs.
• For the food and pharma industries, a bag which fails could put the whole batch at risk.

How Custom Bag Filters Work in Industrial Applications

This working principle is the same for any liquid filter bag. The bag is mounted in a filter housing by means of a perforated basket that keeps the bag in its shape when under pressure.

Dirty liquid is injected, filtered through the bag wall and then the clean liquid exits the housing, with any solids trapped inside the bag. An inside-to-outside flow is used in most cases, keeping any contaminants inside the bag and ensuring an easy change-out of the bag.

• The media (water, oil, solvent, acid) and temperature are selected for the fluid and its temperature.
• The micron rating is selected for the exact cleanliness the operation requires.
• The size and shape are matched to the vessel, not limited by standard housing only.
• The seam and seal are chosen based on the working pressure and hygiene requirements.

The outcome is a bag that holds particles to the required size, seals appropriately and lasts for the desired duration of the process without compromise.

Types of Custom Bag Filters Used in Industry

Custom filter bags are built as per the demands of the application, so the range is diverse. The common types you can find are:

This is where the custom approach fits in. They are not "static boxes"; for example, one bag can combine characteristics, e.g. fully welded, food-grade and non-standard-sized bag with absolute micron rating, when required for the process.

See More: Types of Industrial Filter Bags Used in Dust & Liquid Filtration

Where Custom Bag Filters Are Used in Manufacturing Industries

Custom bag filters for water treatment can process suspended solids in a plant where housing and flow rate rarely suit stock bag size. Custom bag filters for chemical industry can utilize media selected specifically for individual solvents and acids, while custom bag filters for food processing use approved and traceable materials in the case where hygiene decides if the batch is accepted.

Benefits of Using Custom Bag Filters in Industrial Processes

• Correct fit - The bag fits the housing accurately so there's no channelling.
• Accurate degree of filtration - The micron rating reflects your target clarity.
• Correct media - The material is appropriate for the fluid and temperature so the bag doesn't prematurely fail.
• Longer service life - Correct media also means a better fit bag will hold more volume before requiring change-out, and fail less often.
• Compliance built in - If this application is regulated, materials and packaging comply right from the start.

These factors combine to transform filtration from a bothersome operation to a solid and consistent one.

How Custom Bag Filters Improve Filtration Performance

The main performance points in filtration are retention, flow and life. Customizing the bag ensures a better rating on all three points since it is designed rather than a matter of chance.

Retention is enhanced because the micron rating and the media are sized precisely for the particle that must be captured, and absolute ratings can be provided where required. Flow is enhanced; it's sized for the correct amount of surface area, and it's designed for a minimal pressure drop, keeping your fluid moving while not stressing the system.

Life is enhanced because a progressive density or an extended-life media can be specified for heavy service; it traps more dirt before becoming clogged.

For this reason, the best custom bag filters for liquid filtration are not just an "extra fine and tough" version of a standard bag. The bags are balanced for the application so retention, flow and life work together rather than against each other.

Step-by-Step Guide to Choosing the Right Custom Bag Filter

Selecting a custom bag is simple if you work through it sequentially. Industrial filtration bags work when these steps are matched to the actual process.

• Note the type of fluid, temperature, and chemical composition. This dictates the media selection.
• Determine what the cleanliness requirement is, and whether the media needs to be a nominal or absolute rating.
• Check vessel and basket measurements, ensuring the size of the bag and sealing ring are perfectly sized.
• Choose stitched type for general duty and fully welded type for high pressure/hygienic.
• In the food/pharma sector, it is critical to have the media, with FDA approval, traceable and also suitable for packaging.
• For heavily contaminated material, high-capacity or longer-life media may be required.

So, working it through with your supplier, you end up with a bag that fits at the first attempt instead of gaps being found after the first batch.

Custom Bag Filters vs Standard Bag Filters

In conclusion: If your process meets catalogue standards, buy the standard bag. If a trade-off of size, media or micron level would result in bypass, short bag life or off-specification batches, buy the custom bag.

Cost Benefits of Using Custom Bag Filter Solutions

The cost of custom bags individually is often higher, so the savings must be considered on a system level. This is where industrial custom bag filter solutions typically win.

The direct saving: A bag suitable for the load is able to hold more dirt without failure. It therefore needs fewer changes (labour cost and downtime). It lasts longer.

The indirect saving: It is normally more significant. With correct sealing and adequate filtering level, a custom bag protects pumps, membranes and heat exchangers, which cost much more to repair.

There is also a quality saving. In regulated and food processes, preventing one failed batch can often cover a significant number of custom bag runs. Summing these factors, an increased price per unit may mean a decreased cost of operation.

What to Check Before Ordering Custom Bag Filters in Bulk

Large quantities magnify savings, but also errors, so the specification must be locked before volume production. Before you commit, check these:

• Verify that the dimensions and sealing ring are correct for your physical vessels and not for assumed sizes.
• Ensure that the retention is nominal/absolute and is tested.
• All the liquid bag filters in the run are constructed with the identical specifications, with no leakage or bypassing.
• Endorse one sample bag using your own process in the test run, before the run itself.
• Confirm the supplier is able to replicate the same specification.

What ensures quality, from the first box to the last, for buyers who purchase in large volumes, is a manufacturer who is prepared to provide wholesale bag filters with steady custom production.

How to Choose a Reliable Custom Bag Filter Manufacturer

The success of a custom bag relies solely on the manufacturer. For stock products, this may be less important. A capable custom bag filter manufacturer has quality control from the beginning of the raw material to the end product bag and can document this.

Avoid trading companies and search for real in-house manufacturing. An actual filter bag manufacturing company manufactures bags and tests them before shipping, so you could order the micron, media, size, and seam just the way you want.

Check relevant certifications, traceable materials and industries like yours they have worked with. Also verify if they could provide you with both prototypes and repeat bulk orders while maintaining stability in quality, because custom spec does not make sense if not reproducible.

Why Industries Prefer mmp Custom Bag Filter Solutions

mmp Filtration has been producing liquid filter bags since 1994 and has 30+ years of experience making filters for some of the harshest industrial processes. The level of experience is extremely important when it comes to a custom application since determining the correct specification relies heavily on the real-world behaviour of various fluids, pressure, and contamination.

• mmp manufactures its own range of filtration products and checks each bag before use to establish its micron retention capabilities and ensure correct sealing without by-pass.
• It uses a range of materials, such as polypropylene, Polyester, Nylon, PTFE, and carbon media, so a material exists for water, chemicals, oils, and high-temperature liquids.
• It produces bags from 1 to 200 microns and stock sizes 1 to 6, in addition to special sizes when the housing requires it.
• mmp is a preferred supplier for OEM's and big industrial customers across India and overseas, with export packaging and uniform quality.