When you’re specifying filtration for a high flow process, the choice often comes down to two options: bag filters and cartridge filters. Both remove particulate contamination effectively, but in different ways. In this blog, we will discuss the differences between bag filters and cartridge filters and which is best for your high-flow application.
Bag Filters
Bag filters use a fabric bag housed in a single vessel, and liquid flows from the inside out. Particles are trapped inside the bag as the filtrate passes through the media wall. A single bag can offer a generous surface area within a compact housing.
Cartridge Filters
Cartridge filters are available in different formats depending on the filtration requirement. Pleated cartridges use rigid, pleated elements that pack a large amount of filter media into a small area, providing a high surface area relative to their size. Spun cartridges use depth filtration, capturing contaminants throughout the filter media to prioritise dirt-holding capacity and provide effective particulate removal.
Flow Rate and Surface Area
This is where the two technologies start to separate for demanding applications.
Bag filters generally offer more surface area per unit of housing volume than a single cartridge. This means lower pressure drop at high flow rates and less frequent replacements when the contamination loading is heavy. For coarser to mid-range filtration of 1 micron and above, bag filters tend to handle high flow rates with less resistance.
Cartridge filters can match or exceed bag surface area by using multi-cartridge housings. However, as flow rates increase, so does the number and size of cartridges needed. This increases the housing footprint and the cost of consumables. Cartridges hold a real advantage at finer micron ratings, as pleated media can achieve absolute ratings down into the sub-micron range that bags usually can’t match.
Dirt-Holding Capacity, Replacement Frequency, and Running Costs
Dirt-holding capacity is incredibly important for high flow rates carrying a significant particulate load. This is because it drives operating costs just as much as the flow rate.
Bag filters tend to hold more contaminants before differential pressure builds to the point of replacement, which means longer service intervals and less downtime.
Cartridges, however, can clog up faster under a heavy load, which means more frequent (and expensive) replacements, unless you protect them with a pre-filter.
On pure running costs, bag filters are usually cheaper to operate for high-flow, high-loading jobs.
Footprint
For the same flow rate, a bag housing is usually more compact than a housing full of cartridges, especially for coarser filtration grades. If floor space is tight, that alone is a great feature to weigh up.
Which Should I Choose?
In a nutshell:
- Choose bag filters – if you’re dealing with high flow, moderate-to-heavy dirt loading, and don’t need super-fine filtration. You’ll benefit from lower running costs and fewer replacements, which saves you even more money in the long run.
- Choose cartridge filters – if you need fine or absolute micron ratings, or specific media chemistry for your fluid.
- Combine the two – if you need both. Use bags as a cost-effective first stage to catch the bulk of the particulate, then finish with the cartridge for the fine polish. This stops your cartridge from clogging up too fast and provides a more efficient process.
Not Sure Which Fits Your Process Best?
The right choice depends on your flow rate, the amount of particulate in your fluid, what micron rating you need, and what the fluid you’re working with actually is. At Fileder, we help customers work through exactly this across industrial, water treatment, and process applications. Get in touch with our technical team today if you’d like advice on the right filtration for your application.
