Chemical and petrochemical processes demand filtration that withstands 120 °C continuous service, 16 bar differential pressure, and 0.5 micron particulate removal — all while maintaining compliance with ISO fugitive emission limits. This bulletin addresses how KOSA Filter’s Liquid Filtration product line meets those requirements in high-purity liquid streams containing aggressive solvents, chlorinated hydrocarbons, or oxidizing acids. We focus on material integrity, sealing reliability, and compatibility verification — not marketing claims.
Material Selection Beyond the Grade
316L stainless steel is specified for corrosion resistance, but its performance depends on surface finish, heat-affected zone control during welding, and post-fabrication passivation. All Liquid Filtration housings undergo electropolishing to Ra ≤ 0.4 µm, reducing crevice initiation risk in chloride-rich environments. The FZ Top Entry Bag Filter Housing and Side Entry Bag Filter Vessel both use full-penetration orbital welds verified by dye penetrant testing. Chemical compatibility must be confirmed per fluid composition — not just bulk phase, but also trace contaminants like HCl or Fe³⁺ ions that accelerate localized attack.
Sealing Architecture for Emission Control
ISO compliance hinges on gasket geometry, bolting sequence, and flange face integrity — not just gasket material. The V-clamp Quick Open Multi-bag Filter Vessel uses dual O-ring grooves with fluorosilicone elastomers rated to 200 °C. In contrast, the Economical Bag Filter Housing relies on single-lip silicone gaskets suitable only up to 120 °C. Rotating Open Multi-bag Housing incorporates torque-controlled clamping with load-indicating washers. We typically observe 30–40% lower fugitive emissions during commissioning when bolt tension is verified with calibrated tools rather than torque-only methods.
Filter Media Trade-offs in Aggressive Service
Selecting between Polyester Needle Felt Filter Bag and Polypropylene Needle Felt Filter Bag involves a trade-off: PP offers superior resistance to strong alkalis but degrades above 95 °C; polyester retains strength to 130 °C yet suffers hydrolysis in hot, humid caustic solutions. The Multi-layer High Efficiency Filter Bag sacrifices flow capacity at the cost of higher beta-ratio retention for sub-micron particles. Nylon Monofilament Filter Bag provides excellent abrasion resistance but requires pH > 4.5 to avoid amide bond cleavage. Oil Absorption Filter Bag and Activated Carbon Filter Bag are chemically inert only within defined adsorption windows — regeneration cycles must be validated per solvent polarity index.
| Filter Type | Max Temp (°C) | Acid Resistance | Alkali Resistance |
|---|---|---|---|
| SS316 wire mesh filter bag | 450 | Excellent | Poor |
| Membrane Pleated Filter Cartridge | 80 | Good | Fair |
| Yarn Wound String Filter Cartridge | 60 | Fair | Good |
| High Flow Filter Cartridge | 100 | Good | Good |
The table summarizes thermal and chemical boundaries across four media types.
Verification Protocol for End Users
End users must request mill test reports (EN 3.1) for all wetted 316L components and verify chemical compatibility using KOSA’s published resistance matrix — cross-referenced against actual process fluid analysis, not generic “caustic solution” assumptions. ATEX certification does not apply to any Liquid Filtration housing unless explicitly configured with explosion-proof instrumentation interfaces. These units are unsuitable for vapor-phase service or applications involving unconfined hydrogen peroxide decomposition. Avoid using Welded Filter Bag in systems with frequent thermal cycling above 150 °C due to seam fatigue limits.
- Verify surface roughness (Ra) on all internal welds before acceptance
- Confirm gasket compression set data under sustained temperature and pressure
- Test filter media extractables per USP <661> when handling pharmaceutical intermediates
Integration with Broader Filtration Strategy
While this bulletin focuses on liquid-phase filtration, engineers should assess whether particulate loading originates upstream in gas or dust streams. For example, catalyst fines entering a reactor effluent stream may originate from Dust & Flue-Gas Filtration equipment upstream. Similarly, moisture carryover from compressed air systems can compromise Hydraulic Oil Filter Cartridge life — making coordination with Air & HVAC Filtration critical. In practice, we find integrated system audits reduce unscheduled filter change frequency by 22–35% versus isolated housing upgrades.
Common questions on liquid filtration
Is a bag housing or a cartridge housing the right choice?
Bag housings hold one to twenty-three bags and suit a higher solids load, because a loaded bag can be lifted out whole. Cartridge housings pack four to eighteen elements into a smaller footprint and hold a seal more easily at higher differential pressure.
Which sizes and ratings are standard?
Cartridge vessels are built around 5 inch, 10 inch, 20 inch, 30 inch and 40 inch element lengths. Bag housings use Size 1 with a 15 inch basket and Size 2 with a 30 inch basket. Felt and monofilament bags are commonly rated at 1, 10, 25, 75, 100 and 200 micron.
Does a finer micron rating always mean cleaner product?
No. A finer element removes more, but it also loads faster and raises differential pressure sooner, so the change-out interval in days shortens. The rating has to be chosen against the particle size you actually need to remove, not against the finest one available.