SMS Bag Filter
Stitched or Welded Construction, Multi-Layer Depth Filtration and High Dirt-Holding Capacity
The SMS bag filter is a stitched or welded depth filter whose three-layer spunbond-meltblown-spunbond structure retains gel-like and deformable particles with high efficiency in the 0.5–10 µm range.
100–180 mm
230–810 mm
0.5, 0.8, 1, 5, 10 µm
90°C (194°F)
What Is an SMS Bag Filter?
SMS bag filters have a multi-layer structure in which three different functional layers are combined by lamination. There is a spunbond polypropylene layer on the inner and outer surfaces and a meltblown polypropylene main filtration medium between them. This three-layer arrangement provides both high dirt-holding capacity and a low risk of fibre migration at the same time.
Unlike standard single-layer felt or woven bag filters, the very fine fibre structure of the meltblown layer in SMS bags also retains gel-like, semi-solid and deformable particles effectively. The spunbond layers stop these fine meltblown fibres from breaking off and getting into the cleaned liquid. SMS bag filters come into play in demanding processes where conventional felt or woven surfaces fall short.
Product Identity and Technical Summary
SMS bag filters are made by joining a meltblown polypropylene main filtration layer to
spunbond polypropylene inner and outer layers by stitching or welding. With high-efficiency ratings from 0.5 µm to 10 µm and a multi-layer structure, they achieve high dirt-holding capacity. The stitched or welded sealing ring gives maximum sealing assurance at operating temperatures up to 90 °C. The raw material, free of silicone and abrasives, adds an extra layer of assurance in processes that require a fine surface finish.
Key Technical and Structural Features
- Material (Main Layer)
- Meltblown Polypropylene
- Inner and Outer Layers
- Spunbond Polypropylene
- Micron Rating
- 0.5 µm · 0.8 µm
- 1 µm · 5 µm · 10 µm (high efficiency)
- Diameter / Length
- Ø 100–180 mm diameter · 230–810 mm length
- Filtration Surface Area
- 0.50 m²
- Max. Operating Temperature
- 90°C (194°F)
- Max. Differential Pressure
- 2.5 bar
- Recommended Change-Out Pressure
- 1.5 – 2 bar
- Max. Flow Rate
- 12 m³/h (for a #02 housing)
- Dirt-Holding Capacity
- High (multi-layer depth structure)
- Surface Finish
- Stitched or welded construction
- Binder Content
- Free of silicone and abrasives
Filtration Architecture and Working Principle
SMS bag filters pass dirty liquid through a graded layer structure in a three-stage treatment process. Each step complements the previous one; in the end, both large and sub-micron particles are removed from the system.
Filtration takes place inside-out: dirty process liquid enters the bag and particles are retained in the bag’s layers. The filtered clean liquid collects in the space between the bag and the body and leaves through the outlet. The stainless support basket on the outside keeps the bag in shape at high differential pressures.
Pre-Filtration
Dirty liquid enters the bag and first meets the inner spunbond layer. This layer retains large particles as a pre-stage, preventing early clogging of the main meltblown layer.
Meltblown Depth Filtration
The liquid that passes through the inner layer reaches the main meltblown polypropylene layer. The dense, fine fibre structure of this layer traps gel-like particles in depth.
Outer Layer and Sealing
Advantages of the SMS Bag Filter
Thanks to their three-layer structure, SMS bag filters combine high dirt-holding capacity and a low risk of fibre migration in the same product. In demanding processes that must retain gel-like and deformable
particles, they offer a clear performance advantage over standard felt and woven bags.
- High Dirt-Holding Capacity
- High dirt-holding capacity thanks to the multi-layer depth structure; longer run time with a single bag.
- Multi-Layer Depth Filtration
- The three-layer structure retains a wider range of particles than single-layer felt or woven bags.
- Uninterrupted Sealing and Leak Assurance
- The sealing ring seats on the housing surface and reduces the risk of leaks.
- Minimal Fibre Migration
- Spunbond layers on both sides significantly reduce micro-fibre escape.
- Silicone-Free Production
- Raw material free of silicone and abrasives; used safely in fine-surface processes.
- High Efficiency
- Ratings from 0.5 µm to 10 µm with higher efficiency than standard bag filters.
Bag Diameter and Length Options
SMS bag filters are made in diameters of 100–180 mm and lengths of 230–810 mm, in standard sizes of 180 × 430, 180 × 810, 100 × 230 and 100 × 380 mm. Because of the material thickness required by the multi-layer laminated structure, diameter and length tolerances are offered within a narrower range than standard single-layer felt and woven bags; housing compatibility must always be confirmed.
100mm Diameter
Suitable for small-scale systems and laboratory-type filter housings.
180mm Diameter
The industry-standard size and the most widely used size for high-flow systems.
Custom Manufacturing
Bags can be made to sample for older or imported special equipment.
- 180 × 430 mm
- Standard Large Diameter • Short Length (~0.25 m² Filter Area)
- 180 × 810 mm
- Standard Large Diameter • Long Length (~0.50 m² Filter Area • Most Common)
- 100 × 230 mm
- Compact Small Diameter • Short Length (~0.08 m² Filter Area)
- 100 × 380 mm
- Compact Small Diameter • Long Length (~0.14 m² Filter Area)
Micron Options and Precision
| Micron | Application |
|---|---|
| 0.5 µm | Ultra-fine filtration; pharmaceutical, electronics and high-purity chemical lines |
| 0.8 µm | Very fine filtration; fine chemical processes and microelectronics coolants |
| 1 µm | Precision oil and chemical process lines |
| 5 µm | General-purpose fine filtration; final-stage filtration of paints and coatings |
| 10 µm | Medium precision; oil and slurry filtration, hydraulic systems |
Collar Types and Adapters
In SMS bag filters, sealing is provided by a stitched or welded polypropylene (PP) flange or a stainless steel snap-ring collar, depending on the filter housing design and process conditions.
PP Ring (Plastic Ring)
Polypropylene ring, stitched or welded. Used where full chemical resistance is required.
Snap Ring (Steel Ring)
Stainless steel ring. The most widely used, economical standard collar.
Engineer's Note
- Senior Process Engineer
- 15+ Years of Field Experience
- Field-Test Approved
The most common problem we see in the field with SMS (three-layer composite) bag filters is connecting them directly to raw lines without coarse pre-filtration, overlooking the fact that this is a higher-efficiency bag filter than standard bags. When the dense inner meltblown microfibre layer saturates early with coarse particles, differential pressure rises quickly and the filter’s economic service life is shortened.
When should it be chosen?
They should be chosen for lines where standard felt bags fall short and high-efficiency bag filtration and clarity are the goal (fine syrups, soft drinks, chemical solvents and microelectronics process water). Because the outer spunbond layer completely prevents fibre shedding, it gives excellent protection ahead of fine final filtration.
When should it not be chosen?
They should not be used on their own in processes without pre-treatment that carry a high load of coarse sediment (>100 µm), with hot fluids above 90 °C, or in environments containing strong oxidising chemicals; a coarse pre-filtration stage must always be installed upstream.
Application and Selection Criteria
- Housing and Basket Fit
- Because of the multi-layer structure, the tolerance range is narrow; confirm the bag diameter and length against the housing and support basket dimensions before ordering.
- Pre-Filtration
- On lines with a high load of coarse sediment, place a felt or woven pre-filter ahead of the SMS bag; reserve the meltblown layer for fine particles only.
- Temperature and Chemical Limits
- The polypropylene construction operates up to 90 °C; it should not be used above this temperature or on lines containing strong oxidising chemicals.
Industry Applications
Bag filters suited to different process needs are used across a wide range of industrial applications to protect product quality, safeguard equipment and support production continuity.
01
Vegetable Oil
Clarity, purity and shelf life in vegetable oil and refining.
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02
Pipe and Profile
Cooling water filtration in pipe and profile extrusion.
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03
Paint Industry
Surface quality and pigment filtration in the paint industry.
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04
Glass Industry
Furnace and process filtration in the glass industry.
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05
Dialysis Centers
Water preparation and process filtration in dialysis centers.
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06
Foundry Industry
Equipment protection and dust filtration in foundries.
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07
Industrial Oil
Filtration in industrial oil production and recovery.
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08
Energy and Biogas
Maximum efficiency and turbine protection in energy and biogas.
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09
Recycling
Filtration for efficiency and environmental compliance in recycling.
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10
Food and Beverage
Hygienic filtration in food and beverage.
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11
Pharmaceuticals and Biotechnology
GMP-compliant sterile filtration in pharmaceuticals and biotechnology.
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12
Paper and Packaging
Process water filtration in paper and packaging.
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13
Chemical Industry
Corrosion-resistant, safe filtration in the chemical industry.
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14
Cosmetics
Microbiological safety and precision filtration in cosmetics.
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15
Machinery
Precision and technical filtration in the machinery industry.
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16
Printing and Ink
Flawless color and print quality in printing and ink.
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17
Metal and Surface Treatment
Flawless surfaces and bath stability in metal and surface treatment.
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18
Forest Products
Resin and glue filtration in forest products and furniture.
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19
Automotive
Precision process filtration for zero defects in automotive manufacturing.
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20
Oil and Petrochemicals
Equipment protection and process safety in oil and petrochemicals.
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21
Plastic Packaging
Precision process filtration and raw material purity in plastic packaging.
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22
Plastic Injection Molding
Cooling and hydraulic filtration in plastic injection molding.
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23
Water and Environment
Recovery filtration in water and environmental technologies.
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24
Shipyards and Marine
Operational safety and efficiency in shipyards and marine.
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Performance Parameters
The field performance of SMS multi-layer bag filters is assessed on the balanced flow permeability of the spunbond and meltblown layers, the balance between high-efficiency particle retention and service life, and keeping the risk of leakage under control at the body joint.
- High Flow
- Maximum liquid throughput at low differential pressure thanks to the large surface area and optimised pore structure.
- Micron / Service Life Balance
- Service life depends not only on the micron rating but also on the bag's filtration surface area; when the right micron rating and the right bag length are chosen together, you get the required clarity and a longer time to clogging.
- Sealing
- Thanks to the sealing ring that seats on the housing surface, the risk of bypass (leakage) is minimised.
Filter Selection Technical Checklist
- Chemical Nature of the Fluid
- The polypropylene-based construction provides general chemical compatibility across a wide pH range.
- Operating Temperature
- Stable operation up to 90 °C; above that, an alternative material should be considered.
- Required Cleanliness Level
- If there are gel-like or deformable particles, the SMS construction should be preferred over standard felt and woven filters.
- Flow Rate
- The multi-layer construction gives a balanced pressure drop in high-flow systems.
- Contamination Load
- In processes with a high dirt load, the multi-layer depth structure gives a long service life.
- Placement / Installation
- Place the bag carefully in the filter basket to avoid air pockets.
- Food Approvals
- If there is food contact, confirm the certified status of the raw material.
- Maximum Pressure
- Withstands up to 2.5 bar; system pressure must be kept below this limit.
- Cost Sensitivity
- For an economical solution with a low contamination load, a standard felt bag filter should be considered.
Points to Watch During Use
For SMS multi-layer bag filters to deliver maximum filtration efficiency and a long service life, correct installation, controlled pressure management and timely replacement are critical. The operational checkpoints below have been compiled to maintain filter integrity in field applications and to prevent possible bypass risks.
- Preventing Air Pockets
- Place the bag carefully in the filter basket so that no air pockets form.
- Initial Start-Up
- Sudden pressure surges should be avoided when the filter is first put into service.
- Timely Replacement
- Replace the bag within the recommended change-out range of 1.5–2 bar, before excessive pressure loss occurs.
- Basket and Seat Check
- If the old bag shows deformation, tears or damage to the sealing ring, also check the filter basket and the housing surface.
- Even Lid Tightening
- Do not overtighten the housing lid; deformation of the sealing ring creates bypass.
Products that work with this product
SMS Bag Filter
Your Questions Answered
Frequently Asked Questions
At Prosestim, we are committed to answering your questions and providing technical support for our filtration solutions.
What is an SMS bag filter, and how is it different from others?
SMS is a multi-layer bag filter made of spunbond + meltblown + spunbond layers. Unlike conventional single-layer felt or woven bags, it offers both high dirt-holding capacity and the ability to retain gel-like/deformable particles.
When should I replace the bag filter?
Replacement is recommended when the differential pressure reaches 1.5–2 bar; it must be completed before exceeding the maximum of 2.5 bar.
Can SMS bags be washed and reused?
No, the multi-layer laminated construction is single-use; washing can permanently damage the layers.
What is the maximum temperature it can withstand?
SMS bag filters withstand up to 90 °C.
How does an SMS bag filter deliver high flow at such fine micron ratings (0.5 µm)?
Because the multi-layer structure works on the depth filtration principle, it retains particles in a larger volume than a single fine woven surface layer. This allows
an acceptable pressure drop and flow performance to be maintained even at sub-micron ratings.
Why is the risk of bypass lower?
The sealing ring seats fully on the housing surface; with the welded ring option there are no stitch holes, so the risk of leakage is lower still.
Do you manufacture custom sizes?
Standard sizes are 100–180 mm in diameter and 230–810 mm in length (180 × 430, 180 × 810, 100 × 230 and 100 × 380 mm). For special requirements outside these sizes, please consult our team.
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