When selecting a depth filter cartridge for industrial water or process liquids, one of the most common comparisons is melt blown vs. string wound filter cartridges.

Both cartridge types are widely used for sediment removal, pre-filtration and general particle control. Both can capture contaminants throughout the depth of the filter rather than relying only on surface filtration.

However, they are manufactured differently and behave differently under changing solids loads, temperature, viscosity and chemical conditions.

In simple terms:

Melt blown filter cartridges are often selected for economical, consistent fine-particle filtration using a graded polypropylene fiber structure.

String wound filter cartridges are often selected where high solids loading, stronger core support, wider material options or higher-temperature capability is required.

INCE filtration manufactures both melt blown and string wound filter cartridges for industrial water treatment, RO pretreatment, chemicals, food and beverage, electronics, petroleum and general process filtration.

This comparison explains the differences and helps you choose the right cartridge for your application.

Melt Blown vs. String Wound Filter Cartridges: Quick Comparison

Feature	Melt Blown Filter Cartridge	String Wound Filter Cartridge
Filtration mechanism	Depth filtration	Depth filtration
Construction	Thermally formed fine fibers	Yarn wound around a center core
Common material	Polypropylene	PP, cotton, glass fiber
INCE filtration micron range	1–60 µm	1–100 µm
Core	Coreless or supported depending on design	PP or stainless-steel core
Fine particle control	Very suitable	Suitable depending on winding grade
Heavy solids loading	Good with graded-density design	Very suitable for many high-load applications
Temperature flexibility	Mainly determined by PP	Wider range with cotton or glass fiber
Chemical compatibility	Good for many PP-compatible liquids	Depends on yarn and core
Typical use	RO pretreatment, process water, chemicals	Industrial water, oils, chemicals, inks
Main advantage	Consistent economical depth filtration	Material and structural flexibility

The correct choice should be based on the liquid, particle size, contaminant loading, temperature, pressure and filtration objective, rather than cartridge type alone.

What Is a Melt Blown Filter Cartridge?

A melt blown filter cartridge is manufactured by melting thermoplastic polymer—most commonly polypropylene—and forming it into fine fibers.

These fibers are deposited into a porous cylindrical structure.

The resulting cartridge contains a large network of irregular flow paths that capture particles throughout the media depth.

Many industrial melt blown cartridges use a graded-density structure, meaning:

• Larger pores are positioned toward the outside
• Smaller pores are located deeper inside
• Larger contaminants are captured first
• Finer contaminants penetrate deeper before being retained

This helps distribute contamination through more of the cartridge rather than concentrating solids only on the outer surface.

INCE filtration polypropylene melt blown cartridges are available in 1, 3, 5, 10, 20, 30 and 60 micron ratings, with lengths from 10 to 60 inches.

What Is a String Wound Filter Cartridge?

A string wound filter cartridge is made by winding filtration yarn around a rigid porous center core.

The controlled winding pattern creates overlapping channels through which the liquid must travel.

As the yarn density changes through the cartridge depth, particles can be retained at different layers.

Unlike melt blown cartridges, string wound cartridges can use different yarn materials.

INCE filtration string wound filter cartridges are available with:

• Polypropylene yarn
• Absorbent cotton yarn
• Glass fiber yarn

and can use:

• Polypropylene center cores
• Stainless-steel center cores

This flexibility makes string wound cartridges useful for a broad range of industrial liquids and operating temperatures.

1. Filtration Structure

The biggest difference between melt blown and string wound cartridges is how the depth filtration structure is created.

Melt Blown

Melt blown media uses thousands of randomly distributed thermoplastic fibers.

The result is a continuous fibrous matrix with tortuous flow paths.

A properly designed graded-density melt blown cartridge allows larger particles to load in the outer layers while finer contamination is captured deeper inside.

String Wound

String wound cartridges create filtration channels mechanically by winding yarn around a center core.

The filtration characteristics are controlled by:

• Yarn diameter
• Winding tension
• Winding pattern
• Yarn density
• Number of layers

This produces a structured depth-filtration path.

Key Difference

Melt blown filtration depends mainly on the fiber matrix and pore gradient.

String wound filtration depends mainly on the yarn material and winding geometry.

2. Filtration Accuracy

Both technologies are available in multiple micron ratings.

However, the micron number should not be treated as the only measure of performance.

A nominal 5 micron string wound cartridge and a 5 micron melt blown cartridge may not provide identical particle-retention efficiency.

Performance depends on:

• Media design
• Manufacturing control
• Flow rate
• Particle shape
• Liquid viscosity
• Differential pressure

INCE filtration melt blown cartridges cover approximately 1–60 µm, while INCE filtration string wound cartridges extend from 1–100 µm.

For general fine sediment removal and RO pretreatment, melt blown PP cartridges are commonly selected.

For broader coarse-to-fine industrial filtration, string wound cartridges provide additional flexibility.

3. Dirt-Holding Capacity

Both cartridge designs can provide good dirt-holding capacity because both operate as depth filters.

However, their loading behavior differs.

Melt Blown

A graded melt blown structure distributes particles through different fiber layers.

This is particularly useful when the liquid contains a mixture of fine and medium-sized suspended contaminants.

String Wound

The open outer winding and progressively tighter inner structure can handle liquids with broader particle distributions and significant sediment loading.

String wound filters are therefore commonly considered for:

• Well water
• Cooling water
• Industrial process water
• Paints and inks
• Oils
• High-solids process liquids

Which Holds More Dirt?

There is no universal answer.

Actual dirt-holding capacity depends on cartridge diameter, length, media density, micron rating and the contaminant itself.

For that reason, cartridge selection should be based on actual operating conditions rather than assuming one design always lasts longer.

4. Pressure Drop and Flow Rate

Low pressure drop is desirable because excessive resistance can:

• Reduce system flow
• Increase pump load
• Shorten filter service life
• Increase operating cost

Both melt blown and string wound cartridges can provide relatively low initial resistance when correctly sized.

Melt Blown Cartridge

The graded pore structure allows the liquid to move through progressively finer filtration layers.

String Wound Cartridge

The open winding structure can provide relatively free flow through larger external channels before the liquid reaches tighter inner layers.

However, pressure drop depends heavily on micron rating.

A 1 micron cartridge will normally create more resistance than a 50 or 100 micron cartridge of the same format.

Viscosity also matters.

A cartridge filtering water may behave very differently when filtering oil, resin or a viscous coating.

5. Material Options

This is one area where string wound cartridges have a clear design advantage.

Melt Blown Filter Cartridge Materials

Polypropylene is the dominant material.

PP provides:

• Good chemical compatibility
• Low moisture absorption
• Economical manufacturing
• Broad use in water treatment
• Good general industrial performance

INCE filtration melt blown cartridges use polypropylene filtration media and are designed for compatible industrial liquids.

String Wound Filter Cartridge Materials

String wound cartridges offer more material combinations.

PP String Wound

Suitable for:

• Water
• RO pretreatment
• Compatible chemicals
• General process filtration

Cotton String Wound

Cotton can provide good wetting characteristics and can be useful with compatible:

• Oils
• Water
• Process liquids

Glass Fiber String Wound

Glass fiber can be selected for higher-temperature industrial filtration where polypropylene is unsuitable.

This wider material choice makes string wound cartridges especially useful when temperature becomes an important design factor.

6. Temperature Capability

Temperature can significantly influence cartridge selection.

INCE filtration polypropylene melt blown cartridges have a listed maximum operating temperature around 70°C, subject to actual operating conditions and construction.

For INCE filtration string wound cartridges, material selection extends the possible temperature range:

• PP yarn: approximately ≤60°C
• Absorbent cotton: approximately ≤120°C
• Glass fiber: approximately ≤250°C

A stainless-steel center core can also be used where greater mechanical or temperature resistance is required.

Therefore:

For normal-temperature water and chemical filtration, either design may be suitable.

For significantly higher-temperature liquids, string wound cartridges with appropriate yarn and core materials provide more options.

7. Mechanical Strength

A string wound cartridge is built around a center core.

This core can be:

• Polypropylene
• Stainless steel

The core helps resist structural deformation under pressure.

This can be valuable in demanding industrial systems.

Melt blown cartridges may be manufactured with different structural configurations, including versions with center support.

When mechanical strength is important, buyers should check:

• Maximum differential pressure
• Core material
• Temperature
• Cartridge length
• Housing support design

rather than choosing based only on the cartridge name.

8. Typical Melt Blown Filter Cartridge Applications

Melt blown cartridges are widely used where economical depth filtration and fine suspended-solid removal are required.

Common applications include:

RO Pretreatment

Melt blown polypropylene cartridges are frequently installed before RO membranes to reduce suspended contamination.

Industrial Process Water

They can remove sediment, rust and fine suspended particles from plant water systems.

Chemical Processing

PP melt blown cartridges are suitable for many compatible acids, alkalis and chemical solutions.

Electronics

Fine particle reduction is useful for compatible process water and manufacturing liquids.

Food and Beverage

Suitable material configurations can be used for process-water and compatible liquid pre-filtration.

Petroleum Processing

Melt blown cartridges can be used for compatible oils and industrial process liquids where polypropylene is chemically suitable.

9. Typical String Wound Filter Cartridge Applications

String wound cartridges are especially useful where higher solids loading, material flexibility or core strength is required.

Common applications include:

Industrial Water

String wound cartridges can remove:

• Sand
• Rust
• Pipe scale
• Sediment
• Suspended solids

from cooling water, process water and utility systems.

Oils

Cotton or compatible synthetic yarn can be considered for selected oil-filtration applications.

Paints and Inks

The depth-filtration structure can capture particles and agglomerates in compatible coatings, inks and process liquids.

Chemical Processing

Different yarn and core combinations allow string wound cartridges to be adapted to various compatible chemical conditions.

High-Temperature Liquids

Cotton and glass-fiber configurations with suitable center cores provide options where polypropylene temperature limits are insufficient.

Melt Blown vs. String Wound for RO Pretreatment

Both cartridge types can be used before reverse-osmosis systems.

The correct choice depends on feed-water quality.

Melt Blown May Be Better When:

• Fine sediment is the main contaminant
• Consistent PP filtration is desired
• Replacement cost needs to remain low
• Water temperature is moderate

String Wound May Be Better When:

• Sediment loading is high
• The particle-size distribution is broad
• Strong center-core support is required
• Larger coarse particles must be captured upstream

In many systems, cartridge filtration works even better after a coarse upstream filter.

For example:

Bag Filter → String Wound or Melt Blown Cartridge → Fine Cartridge → RO

This prevents expensive downstream elements from carrying the entire solids load.

Melt Blown vs. String Wound for High-Sediment Water

If the water contains large amounts of sand, rust or coarse sediment, a string wound cartridge can be an effective option because its wound depth structure can accommodate broad particle distributions.

However, this does not automatically mean string wound is always better.

A properly designed graded-density melt blown cartridge can also achieve good dirt-loading performance.

The better approach is to examine:

• Total suspended solids
• Particle-size distribution
• Flow rate
• Required micron rating
• Replacement frequency

If filters plug too quickly, adding a coarse pre-filtration stage may provide a bigger improvement than simply switching cartridge technology.

Which Cartridge Is More Economical?

Both melt blown and string wound cartridges are considered economical industrial filter elements.

The purchase price should not be the only factor.

The real filtration cost includes:

Cartridge price + replacement frequency + labor + downtime + disposal + pressure loss

A lower-cost filter that plugs twice as quickly may ultimately cost more.

When comparing cartridges, measure:

• Initial differential pressure
• Operating differential pressure
• Service hours
• Volume filtered
• Cartridge replacement frequency

This gives a much more meaningful comparison than unit price alone.

Can Melt Blown and String Wound Filters Be Used Together?

Yes.

In some industrial systems, they can be installed as different filtration stages.

For example:

50–100 micron string wound → 5–10 micron melt blown → final pleated cartridge

The string wound cartridge removes larger contaminants.

The melt blown cartridge then reduces finer suspended solids.

A high-efficiency pleated cartridge can provide final polishing if required.

A staged system can improve service life and reduce the contaminant load reaching the final filtration stage.

How to Choose Between Melt Blown and String Wound Cartridges

Use the following questions.

Choose Melt Blown When:

• Fine sediment filtration is required
• Polypropylene is chemically compatible
• RO pretreatment is the primary application
• Economical disposable filtration is required
• Operating temperature is within PP limits
• Consistent graded-depth filtration is preferred

Choose String Wound When:

• The liquid has significant sediment loading
• Higher-temperature filtration is required
• Cotton or glass-fiber media is needed
• Strong center-core support is important
• Oil, ink or specialized industrial liquid filtration is involved
• A wider coarse micron range is required

For uncertain applications, testing both configurations under actual process conditions can provide the most reliable answer.

How to Specify a Replacement Cartridge

Before ordering either cartridge, provide more than just the micron rating.

Useful information includes:

1. Filter type — melt blown or string wound
2. Micron rating
3. Cartridge length
4. Outside diameter
5. Inside diameter
6. End-cap configuration
7. Filter media
8. Center-core material
9. Liquid being filtered
10. Operating temperature
11. Flow rate
12. Operating pressure
13. Required quantity

If an existing cartridge is being replaced, provide the model number, drawing or clear photographs.

Melt Blown vs. String Wound Filter Cartridge FAQ

Which filter is better: melt blown or string wound?

Neither is universally better. Melt blown cartridges are often preferred for economical fine sediment filtration, while string wound cartridges offer more yarn, core and temperature options for demanding industrial processes.

Are melt blown filters depth filters?

Yes. Melt blown cartridges use a fibrous depth-filtration structure that captures contaminants throughout the filter media.

Are string wound cartridges depth filters?

Yes. Their wound yarn structure creates multiple filtration layers from the outside toward the center.

Which is better for RO pretreatment?

Both can be used. Melt blown PP filters are common for fine sediment removal, while string wound filters can be useful where sediment loading is higher.

Which filter is better for high temperature?

String wound cartridges generally provide more options because cotton and glass-fiber yarn can be combined with suitable center cores for temperatures beyond standard polypropylene limits.

Which cartridge is better for chemicals?

Chemical compatibility depends on the media, core and gasket materials. PP melt blown and PP string wound cartridges can both work with many compatible chemicals.

Can I replace a string wound cartridge with melt blown?

Possibly, if the dimensions, micron requirement, flow, chemical compatibility and housing fit are suitable. However, the filtration behavior may change, so replacement should be evaluated based on the application.

Melt Blown and String Wound Filter Cartridges from INCE filtration

The choice between melt blown vs. string wound filter cartridges should be based on the actual filtration process rather than assuming one design is always superior.

For economical fine-particle removal, industrial water filtration and RO pretreatment, a polypropylene melt blown cartridge is often a practical choice.

For high solids loading, wider material selection, stronger center-core support or higher operating temperature, a string wound filter cartridge may provide more flexibility.

INCE filtration manufactures both cartridge types for industrial filtration systems.

Available melt blown options include:

• 1–60 micron PP filtration
• 10–60 inch lengths
• Multiple surface finishes
• Multiple end-cap configurations
• Standard and custom dimensions

Available string wound options include:

• 1–100 micron filtration
• PP, cotton and glass-fiber yarn
• PP or stainless-steel cores
• 10–50 inch lengths
• Multiple end-cap options
• Custom winding and OEM configurations

If you are unsure which cartridge is more suitable, send INCE filtration your:

Liquid type
Required micron rating
Flow rate
Operating temperature
Pressure
Contaminant type
Existing cartridge dimensions
Required quantity

INCE filtration can help compare the two designs and recommend a suitable filter cartridge for your process.

Contact INCE filtration for melt blown or string wound filter cartridge selection, OEM manufacturing, replacement matching or a custom quotation.