What Is a PES Pleated Filter Cartridge? Structure, Uses and Benefits

Flow rate, particle retention, and protein binding — these three variables determine whether a PES pleated filter cartridge is the right choice for a process. Get one wrong and either the filter loads before the batch finishes, the product is retained by the membrane, or the contaminant passes through.

A PES pleated filter cartridge uses a polyethersulfone (PES) membrane as the primary filtration layer. It’s used in the pharmaceutical industry, biopharmaceutical processing, food and beverage production, electronics manufacturing, ultrapure water systems, and critical process filtration where high-purity liquid filtration is required.

This article covers the cartridge structure, how it works, key performance features, pore size selection, applications, the comparison with other membrane types, sterilizing filtration validation requirements, and selection guidance.

What Is a PES Pleated Filter Cartridge?

A PES pleated filter cartridge is a membrane pleated filter made with a polyethersulfone membrane as its primary filtration layer. PES is naturally hydrophilic — it wets easily with water-based liquids without needing alcohol pre-wetting for most aqueous filtration applications.

PES membrane filter cartridges are used for clarification, bioburden reduction, sterilizing filtration, and final liquid filtration. The pleated design folds the membrane into a compact structure that maximises the effective filtration area inside a standard cartridge housing.

Common Cartridge Components

• PES membrane — the primary filtration layer
• PP (polypropylene) support and drainage layers — protect the membrane and distribute flow
• Pleated media pack — increases filtration area within the housing
• Inner core and outer cage — provide mechanical support
• End caps and O-rings — seals to prevent bypass leakage

In regulated applications, the validation documents — bacterial retention data, integrity test values, and extractables and leachables data — matter as much as the pore size rating. A pore size alone doesn’t qualify the filter for a specific pharmaceutical or food-contact process.

How Does a PES Pleated Filter Cartridge Work?

Liquid enters the filter housing. It passes through the outer surface of the cartridge, through the pleated PES membrane, and exits through the inner core. Particles, bacteria, colloids, and suspended solids are captured in or on the membrane. Filtered liquid exits clean.

The separation depends on pore size, membrane structure, operating pressure, flow rate, feed liquid quality, and chemical compatibility between the liquid and the membrane material. Change the feed liquid or the operating pressure and the filtration behaviour changes — which is why water flow data from a datasheet doesn’t fully predict performance in a process fluid.

The pleated structure increases effective membrane area inside the same cartridge diameter compared with a flat-sheet design, which supports higher flow rates at a given differential pressure. As contaminants accumulate on and in the membrane, pressure drop rises. A rising pressure drop during a batch is the primary operational indicator that the cartridge is loading and approaching the replacement point.

PES Pleated Filter Cartridge Structure

PES Membrane Layer

The main filtration layer. Made from polyethersulfone polymer processed into a membrane with a defined pore structure. Controls particle and microbial retention. Common pore size options include 0.1, 0.2/0.22, 0.45, 0.65, and 1.0 µm depending on the supplier and product series. Many pharmaceutical-grade PES cartridges use an asymmetric gradient structure that provides a highly porous outer face with finer pores toward the retention layer.

Support and Drainage Layers

Usually polypropylene. Protect the membrane from mechanical damage during filtration and distribute liquid evenly across the membrane surface. Without adequate support layers, local high-flow zones can damage the membrane or reduce filtration efficiency. They also reduce local stress on the membrane during pressure cycles.

Pleated Pack

The membrane, support, and drainage layers are folded together into a tight pleat structure and wound into the cylindrical cartridge form. This is what gives the PES cartridge its high effective filtration area inside a compact housing. A 10-inch cartridge with a pleated PES membrane has significantly more filtration area than a flat-sheet membrane of the same footprint.

Inner Core and Outer Cage

Provide mechanical support to the pleated pack. The inner core collects filtered liquid and channels it toward the outlet. The outer cage holds the pleat structure in shape under operating pressure. Without both, the cartridge can deform or collapse, which bypasses the membrane and voids filtration.

End Caps and Seals

Thermally bonded or hot-melt welded to the cartridge body — no adhesives in quality pharmaceutical-grade designs. O-ring or gasket material (silicone, EPDM, Viton, PTFE-encapsulated) must be selected to match the process liquid chemistry and the sterilization method. Autoclave and SIP cycles impose different material requirements than cold sanitization.

Key Features of PES Membrane Filters

The combination of properties that makes PES a standard pharmaceutical membrane filter:

Hydrophilic surface. PES wets easily with aqueous liquids. No alcohol pre-wetting is typically needed for aqueous filtration applications.

Low protein binding. PES has naturally low non-specific protein adsorption. For biological products, buffers, enzymes, and protein-containing solutions, low protein binding reduces product loss during filtration.

High flow rate. The pleated membrane area supports high liquid throughput at a given pressure, which matters for large-batch processing and high-throughput filtration where time-to-filter is a production constraint.

Low pressure drop. A well-designed PES membrane filter provides high flow with lower flow resistance. This reduces pump load and filtration time, and leaves more operating pressure available for the rest of the system.

Wide chemical compatibility. PES is compatible with many aqueous fluids, buffers, mild chemicals, and selected process liquids. Full compatibility still depends on temperature, concentration, contact time, housing, O-ring material, and process conditions — confirm per application.

Low extractables. Thermally bonded PES cartridges without adhesive components generate lower extractable levels, which is important for pharmaceutical, biopharmaceutical, food, beverage, and electronics applications where product purity is critical.

Asymmetric PES Membrane vs. Symmetric Membrane

Most pharmaceutical-grade PES pleated cartridges use a highly asymmetric membrane structure. The difference matters for dirt holding capacity, flow rate, and service life.

An asymmetric PES membrane has a graded pore structure: larger pores on the outer face capture bigger particles in the outer depth, while finer pores toward the retention layer provide the actual size exclusion. This graduated structure gives the membrane higher dirt holding capacity because particle loading is distributed across depth rather than concentrated at the surface.

Common Pore Sizes and How to Choose

Don’t choose by smallest pore size alone. Smaller pores increase pressure drop and shorten service life if the feed liquid carries significant particle load. For sterile processes, the pore size is a starting point — not the qualification. Confirm bacterial retention data, forward flow and bubble point integrity test values, and validate for the actual process conditions before specifying a cartridge for sterilizing filtration.

For viscous or heavily contaminated feed liquids, use pre-filtration to protect the PES membrane. A coarser cartridge upstream extends the service life of the final PES membrane filter significantly.

PES Pleated Filter Cartridge Applications

Pharmaceutical Industry

Sterilizing filtration is the primary pharmaceutical application — aqueous drug solutions, large-volume parenterals (LVP), small-volume parenterals (SVP), eye drops, antibiotic solutions, buffers, and cleaning solutions. PES cartridges at 0.2/0.22 µm are widely used for final sterilizing filtration when validated. Bioburden reduction before the final filter also uses PES, typically at 0.45 µm.

Biopharmaceutical Processing

• Cell culture media and buffer sterilization
• Protein solutions and enzyme concentration filtration
• Biological intermediates where low protein binding reduces product loss
• Cleaning and disinfection solution filtration

Low protein binding is the deciding factor in biopharmaceutical filtration. PES retains less protein from the product stream than many other membrane types, which matters when product loss has a direct cost or affects yield calculations.

Food and Beverage

Bottled water, mineral water, soft drinks, beer, wine, juice, syrups, and ingredient water. PES cartridges used for microbial stabilization where high flow rates and food-contact material compatibility are both required.

Electronics Industry

Ultrapure water preparation, wet process chemical filtration, and particle control for semiconductor and display panel manufacturing. The low extractables profile of pharmaceutical-grade PES is relevant here — contamination from filter materials can damage sensitive processes.

Laboratory and General Industrial Use

• Aqueous sample preparation, media filtration, and buffer filtration
• Particle removal before analytical testing
• Process water, fine chemical filtration, and cleaning solutions

PES vs. Other Membrane Filter Cartridges

Membrane material determines chemical compatibility, protein binding, surface energy, and what the filter can and can’t contact. The right membrane depends on the process fluid.

PES is typically selected for aqueous liquid filtration where high flow and low protein adsorption are priorities. PTFE is better for aggressive solvents or gas/vent filtration — see LENGE’s

PES is selected for aqueous liquid filtration where high flow and low protein adsorption are priorities. PTFE handles aggressive solvents and gas vent filtration: hydrophilic PTFE pleated filter cartridges cover acid, alkali, and polar aqueous streams.

For broader chemical resistance where both biological compatibility and solvent tolerance are needed: PVDF pleated filter cartridges are the standard alternative to PES.

Where two membrane layers are required for higher retention certainty: double membrane pleated filter cartridges provide dual-layer PES construction with integrity test capability.

Sterilizing Filtration and Validation

0.2 or 0.22 µm PES filters are widely used for sterilizing filtration. But “widely used” doesn’t mean automatically qualified. The FDA’s aseptic processing guidance treats sterilizing filtration as a critical process step that must be validated for the actual product, process conditions, and filter configuration.

Validation needs to address:

• Bacterial retention — typically tested using Brevundimonas diminuta per ASTM F838
• Product compatibility — the actual process fluid, not surrogate water
• Process pressure and maximum differential pressure
• Flow rate and total batch volume
• Temperature and filtration time
• Extractables and leachables for the specific product
• Pre-use and post-use integrity testing (forward flow and/or bubble point)

A catalogue pore size rating alone doesn’t prove the filter retains bacteria under your process conditions. Bacterial retention depends on pressure, flow rate, product chemistry, and the specific filter product — not just the nominal pore size. Validate for the process, not for the catalogue.

How to Choose the Right PES Pleated Filter Cartridge

Step 1: Define the Filtration Goal

Clarification, bioburden reduction, sterilizing filtration, ultrapure water filtration, final product filtration, or prefiltration before a finer membrane. Each goal maps to a different pore size and validation requirement.

Step 2: Select the Pore Size

• 0.45 µm for clarification and bioburden reduction
• 0.2 / 0.22 µm for sterilizing filtration when validated for the specific process
• 0.65 µm or coarser for prefiltration stages protecting a finer final filter

Step 3: Check Flow Rate and Pressure Drop

Confirm the required batch volume and time. Check the supplier’s clean-water flow rate data at a given differential pressure. Review the maximum allowable differential pressure. Undersizing a cartridge for a batch volume causes the cartridge to load before the batch is complete — which either means filter change mid-batch or running above the rated differential pressure.

Step 4: Confirm Chemical Compatibility

Check the process liquid, cleaning agent, and sterilization method against PES compatibility data. Check every wetted component: membrane, support layer, inner core, outer cage, end caps, and O-ring. If any component is incompatible, the system fails even if the membrane itself is compatible.

Step 5: Choose the Cartridge Format

Length: 5, 10, 20, 30, or 40 inch — match to housing and required filtration area.

End cap: DOE, 222, 226, fin, flat, bayonet — must match housing configuration.

O-ring material: silicone, EPDM, Viton, or PTFE-encapsulated — select based on fluid chemistry and sterilization method.

Step 6: Ask for Documents

• Data sheet with flow rate, pressure drop, and pore size data
• Integrity test specification (forward flow and bubble point values for the filter model)
• Bacterial retention data (ASTM F838 or equivalent) for the specific product series
• Extractables and leachables data for pharmaceutical or food applications
• Certificate of quality with lot number traceability

Installation and Use Tips

• Confirm cartridge length, diameter, and end cap configuration against the housing specification before ordering
• Check O-rings for cuts, twisting, or deformation before installation
• Wet the cartridge according to the supplier’s instructions — PES is hydrophilic but pre-wetting method still matters for some configurations
• Install the cartridge straight to avoid partial seating and bypass leakage at the end cap
• Do not exceed the rated maximum differential pressure or operating temperature
• Flush the cartridge if required by the supplier’s instructions before putting into service
• Avoid sudden pressure shocks — bring system up to operating pressure gradually
• Monitor differential pressure during operation; record batch number, installation date, and operating conditions
• Follow the approved SOP for sterilization or sanitization method and chemical concentrations

Maintenance, Replacement and Service Life

Service life depends on feed liquid quality, particle load, flow rate, operating pressure, temperature, and the frequency and type of cleaning or sterilization cycles. There’s no universal calendar-based replacement interval. Track pressure drop and flow rate across the batch or operating period.

Replace When

• Differential pressure reaches the supplier’s or your SOP’s maximum limit
• Flow rate falls below the acceptable threshold for the process
• Pre-use or post-use integrity test fails
• Batch or validation protocol rules require replacement regardless of performance
• Visible damage or seal integrity issues appear

Prefilters upstream extend the service life of final PES membrane cartridges by removing coarser particles before they reach the fine membrane. Don’t extend cartridge use beyond validated limits because it “still flows” — if integrity limits aren’t met, the filter isn’t validated for the process regardless of flow rate.

Common Mistakes to Avoid

• Selecting 0.2 µm without confirming bacterial retention data and integrity test values for the specific filter product
• Using PES with solvents or chemicals that aren’t confirmed as compatible
• Skipping prefiltration for dirty or high-particle feed liquids
• Ignoring pressure drop until the filter is completely blocked
• Mixing incompatible end cap types with the housing
• Reusing cartridges beyond their validated or rated cycle limits
• Forgetting extractables and leachables review for pharmaceutical or food-contact use
• Assuming products from different PES pleated filter cartridge factories have identical performance — they don’t
• Buying from a PES pleated filter cartridge factory without requesting individual test reports, data sheets, and traceability documentation

LENGE PES Pleated Filter Cartridges

LENGE manufactures PES pleated filter cartridges for pharmaceutical, biopharmaceutical, food, beverage, and critical process filtration. Key construction features:

• Naturally hydrophilic PES membrane with asymmetric gradient aperture structure
• High-purity polypropylene support layers, core, cage, and end caps
• Thermal bonding throughout — no adhesives, no chemical binders
• Class 100 production environment
• Low pressure drop and high flow rate design

View LENGE’s PES pleated filter cartridge product page for pore size options, end cap configurations, and cartridge lengths.

The full LENGE pleated filter cartridge range also includes PVDF, PTFE, PFA, nylon, PP, and GF membrane options for different process chemistries and applications.

To match pore size, cartridge length, end cap, O-ring material, and housing design to your process: contact LENGE

Conclusion

A PES pleated filter cartridge is a hydrophilic polyethersulfone membrane cartridge used for high-purity liquid filtration across the pharmaceutical, biopharmaceutical, food, beverage, and electronics industries. The combination of high flow rate, low protein binding, reliable microbial and particle retention, low pressure drop, long service life, and wide chemical compatibility makes it the standard membrane type for aqueous pharmaceutical filtration.

Select by pore size matched to the actual contaminant, process liquid compatibility, flow rate and batch volume, validation requirements, and housing compatibility. For pharmaceutical sterilizing filtration, the product-specific bacterial retention data and integrity test values are the qualifying documents — not the catalogue pore size.

FAQs

What is a PES pleated filter cartridge?

A membrane filter cartridge with a polyethersulfone (PES) membrane as the primary filtration layer. The membrane is folded into pleats to maximise effective filtration area inside a compact cartridge housing. Used for clarification, bioburden reduction, and sterilizing filtration of aqueous liquids in pharmaceutical, biopharmaceutical, food, beverage, and electronics applications.

What does PES stand for in filtration?

Polyethersulfone. It’s a thermoplastic polymer material used as the filtration membrane in pleated cartridge filters. PES is naturally hydrophilic, which means it wets with aqueous liquids without requiring alcohol pre-wetting, and it has low non-specific protein binding.

What is a PES membrane filter used for?

• Sterilizing filtration of pharmaceutical aqueous solutions (LVP, SVP, eye drops, biologics)
• Bioburden reduction before final filtration
• Cell culture media, buffer, and enzyme filtration in biopharmaceutical processing
• Microbial stabilization of beverages, juices, and bottled water
• Ultrapure water and wet process chemical filtration in electronics manufacturing

Is PES membrane hydrophilic?

Yes. PES is naturally hydrophilic. It wets readily with water and water-based liquids. No alcohol pre-wetting is typically needed for aqueous filtration applications, which simplifies handling and reduces process steps.

What pore size is used for sterilizing filtration?

0.2 or 0.22 µm is commonly specified. But the pore size alone doesn’t qualify the filter. For pharmaceutical sterilizing filtration, the specific filter product must be validated for bacterial retention (tested per ASTM F838 using Brevundimonas diminuta) under the actual process conditions: pressure, flow rate, temperature, and product chemistry.

What is the difference between PES and PVDF filters?

Both are hydrophilic membrane materials with low protein binding. PES is the standard for pharmaceutical aqueous filtration where high flow rate and low protein binding are priorities. PVDF (polyvinylidene fluoride) offers broader chemical resistance and is commonly used in biopharmaceutical applications where the process fluid contacts a wider range of solvents or chemicals that PES may not tolerate.

What is the difference between PES and PTFE filters?

PES is hydrophilic — suited to aqueous liquid filtration. Standard PTFE is hydrophobic — it repels water and is primarily used for gas filtration, tank venting, and aggressive solvent filtration where aqueous liquids don’t contact the membrane. Hydrophilic-modified PTFE is available for aqueous applications where strong chemical resistance is needed, but PES is the simpler and more commonly specified option for standard pharmaceutical aqueous filtration.

Why does a pleated filter cartridge have a high flow rate?

Because of the filtration area. Pleating the membrane sheet folds more membrane into the same cartridge footprint than a flat sheet would allow. More membrane area at the same housing size means lower velocity per unit of membrane area at a given flow rate — which means lower pressure drop and longer time before the filter loads.

What causes pressure drop in PES cartridge filters?

Particle and contaminant accumulation on and in the membrane as filtration progresses. Particles block pore pathways, increasing the resistance to flow. Pressure drop rises as the filter loads. When pressure drop reaches the limit, the filter needs replacement or regeneration. Starting with adequate prefiltration for dirty feeds reduces the rate of pressure drop rise.

How long does a PES pleated filter cartridge last?

No single answer. Service life depends on feed liquid quality, particle load, flow rate, operating temperature, and the frequency and type of cleaning or sterilization cycles. A cartridge in a clean pharmaceutical buffer system at low flow lasts much longer than one filtering a high-turbidity process liquid at high flow. Track pressure drop and flow rate rather than operating hours or calendar time.

Can PES pleated cartridges be used in the pharmaceutical industry?

Yes. PES pleated filter cartridges are one of the most widely used pharmaceutical liquid filtration products. They’re specified for LVP, SVP, eye drops, biologics, cell culture media, buffers, antibiotic solutions, and cleaning solutions. Pharmaceutical applications require individual lot certificates, integrity test specification, bacterial retention data, and extractables and leachables documentation.

What should I ask a PES pleated filter cartridge factory before buying?

• What is the integrity test specification — forward flow limit and bubble point for the specific product and pore size?
• What bacterial retention data exists, and under what test conditions (ASTM F838 or equivalent)?
• What extractables and leachables data is available for pharmaceutical or food-contact applications?
• Are individual lot test certificates provided with each shipment?
• What production environment is used, and is it ISO-classified?
• What end cap, O-ring, and core/cage material options are available?

Sources

1. LENGE Purification — "PES Pleated Filter Cartridge" (Accessed July 2026)
2. LENGE Purification — "PES Filter Series" (Accessed July 2026)
3. Donaldson — "PES Liquid Filter Cartridges" (Accessed July 2026)
4. Sartorius — "Sartopore Evo® PES Membrane Filter" (Accessed July 2026)
5. Merck Millipore — "PES Membrane Filter, 0.22 μm Pore Size" (Accessed July 2026)
6. Merck Millipore — "Membrane Filtration Guide" (Published 2017)
7. FDA — "Sterile Drug Products Produced by Aseptic Processing" (Guidance issued September 2004)
8. ASTM International — "ASTM F838-20 Bacterial Retention of Membrane Filters" (Accessed July 2026)
9. Brother Filtration — "PES Membrane Filter Cartridge Manufacturer" (Accessed July 2026)
10. Darlly Filtration — "PES Membrane Pleated Filter Cartridge" (Accessed July 2026)