How to Choose the Sealing Ring for a Pleated Filter Cartridge?

In daily operation and maintenance of precision filtration for water treatment, food & beverage, pharmaceutical and chemical industries, sealing rings play a decisive role in determining the stability of pleated filter systems, maintenance costs and the cleanliness of filtered media.

Functions of Sealing O-Rings

Most users regard sealing rings as ordinary spare parts for sealing only, yet they perform multiple core functions for filter equipment operation, all of which directly impact production efficiency:

① Tight sealing to prevent filter bypass 

The primary function of sealing rings is to fill gaps between Filter Cartridges and filter housings, thoroughly stop liquid and gas leakage, and stabilize operating differential pressure. Poor sealing allows unfiltered fluid to flow through gaps directly, causing filter bypass and rendering even high-precision filter cartridges useless.

② Vibration buffering to extend service life of equipment and cartridges 

Continuous vibration occurs during equipment operation. Sealing rings cushion rigid friction caused by vibration, preventing abrasion from direct collision between cartridges and housings, cutting cartridge wastage and equipment breakdown risks, and lowering replacement & maintenance expenses.

③ Contamination isolation to guarantee fluid cleanliness 

In high-precision filtration applications, ingress of dust, debris and microbes directly impairs finished product quality. Properly matched premium sealing rings fully seal the filter chamber to block external contaminants, eliminate secondary pollution at source and satisfy strict hygiene requirements for water purification, pharmaceuticals and precision electronics industries.

④ Positioning & fixation for stable equipment running

Sealing rings help lock filter cartridges in place, preventing shifting, loosening or bouncing under high working pressure, ensuring steady continuous operation of the whole filtration system and unplanned shutdowns.

Core Principles for O-Ring Selection

1. Material Selection

Material is the key factor determining an O-ring's resistance to corrosion, aging and swelling. Each fluid medium requires a dedicated elastomer; random material interchange is the top mistake in selection. Below are mainstream materials and their applicable working conditions:

Food-Grade Silicone 

Non-toxic, odorless, hygienic and heat-resistant with outstanding elasticity and dimensional stability. It is the preferred option for ambient and medium-temperature filtration of purified water, potable water, beverages, wine, dairy products and biopharmaceuticals. Cost-effective and fully compliant with food contact regulations.

EPDM (Ethylene Propylene Diene Monomer) Excellent resistance to weathering, ozone and aging. Suitable for most general industrial filtration including weak acid/alkali solutions, industrial circulating water and low-temperature liquids. Wear-resistant for uninterrupted factory operation and widely used in industrial water treatment.

NBR (Nitrile Butadiene Rubber) Features superior oil resistance, abrasion resistance and cost competitiveness. Ideal for filtration of engine oil, diesel, hydraulic oil, animal/vegetable fats and oily wastewater. Outstanding anti-swelling property against oils, high tear resistance and mechanical strength, making it the economical choice for ambient-temperature oily industrial filtration.

Viton (Fluororubber) Exceptional resistance to extreme temperatures, harsh chemicals, oils and organic solvents. Capable of withstanding strong acids, alkalis, chemical solvents and hot oily fluids, serving as the primary choice for heavy-duty chemical filtration.

PTFE (Polytetrafluoroethylene) Near-inert to nearly all chemicals with zero extractables and no contamination risk. Specially used for high-purity reagent, precision electronic fluid and high-end fine chemical filtration to meet strict high-precision and ultra-clean production standards.

2. How to Select O-Rings for Pleated Small Cartridge Filters

Small pleated filter cartridges feature intricate construction and compact filter housing cavities, which demand superior fitting precision. Accordingly, their O-rings must meet stringent standards in elasticity, dimensional accuracy and material stability. Mismatched sealing components will cause filter bypass directly, nullifying the high-precision performance of small pleated filters, raising spare part replacement costs and triggering unplanned production downtime.

① Polypropylene (PP) Small Pleated Filter Cartridges

Hongtek PP Pleated Filter Cartridges are manufactured from premium polypropylene membrane with zero fiber shedding, excellent acid & alkali resistance, strong impact tolerance and high dirt-holding capacity. They fit most general precision filtration scenarios such as industrial water treatment, pre-treatment of purified water, conventional chemical processing and oily fluid prefiltration. Though PP enjoys broad chemical compatibility, not all O-ring grades work for it. EPDM or food-grade silicone O-rings are recommended for regular service conditions, while NBR O-rings are selected for oily media. Perfect dimensional match and proper elasticity effectively prevent loosening, leakage and material swelling, securing long-term stable operation of PP cartridges, extending service life and suiting continuous mass filtration in manufacturing plants.

② PES Pleated Filter Cartridges

Our PES Series PES Pleated Membrane Filter Cartridges adopt polyethersulfone membrane characterized by consistent pore size, high filtration efficiency, low fluid adsorption, resistance to high-temperature sterilization and minimal extractables. They are specially designed for pharmaceutical processing, biological preparations, semiconductor ultrapure water and premium food precision filtration. Focused on ultra-cleanliness, high accuracy and bacteria-free performance, PES cartridges cannot be paired with ordinary rubber O-rings. Medical-grade silicone, DuPont Viton fluoroelastomer or high-purity PTFE O-rings are mandatory options to avoid impurity leaching, particle shedding and contamination from degraded seals, preserving the ultra-high purity filtration performance of PES cartridges and complying with strict industrial hygiene specifications.

Conclusion

In short, premium small pleated filter cartridges must be equipped with custom-matched O-rings. The filter cartridge delivers precise filtration while the O-ring guarantees reliable sealing; the two components complement each other and are indispensable. Improper O-ring selection disables the performance of even top-grade PP and PES small pleated filters, leading to frequent breakdowns and higher maintenance costs. Only a well-matched complete set can ensure stable filtration, longer service life of filter consumables and full compliance with production specifications.