PP Pleated Filter Cartridges: Nominal Rate VS Absolute Rate

Within the industrial filtration, water treatment and fluid purification industries, most buyers fall into the same habit when purchasing pleated filter cartridges: they only focus on micron rating. PP Pleated filter cartridges available on the market are categorized into two core standards: nominal rate and absolute rate. The two types differ drastically in filtration capacity, testing standards and applicable working conditions - this is the fundamental reason why filters with the same micron rating produce inconsistent results. Today, we will thoroughly break down the key differences between nominal efficiency and absolute efficiency pleated filter cartridges.

01. Definitions of Nominal Rating and Absolute Rating

1. Nominal Rating (Stated Rating)

Nominal rating refers to the basic stated precision widely adopted across the industry, and serves as the marking standard for most standard pleated filter cartridges available on the market. Its core definition is that the filter cartridge can trap most contaminants of the rated particle size, yet not 100% of them.

Test standards for such filter cartridges are relatively lenient with a high tolerance margin. Under standard test conditions, a small quantity of contaminants matching the rated particle size is permitted to pass through the filter medium. To put it simply, a pleated filter cartridge marked with a 1 μm nominal rating can only intercept most contaminants of 1 μm and larger, while trace fine particles will still penetrate the cartridge.

Pleated filter cartridges with nominal rating feature cost-effectiveness and basic filtration performance. Supported by mature manufacturing processes and low production costs, they are primarily applied to low-demand scenarios including domestic water purification, industrial pre-treatment and general water circulation. They are the most versatile basic filter cartridge type.

2. Absolute Rating (Precision Filtration)

Absolute rating is a stringent industrial filtration standard and a core parameter for Pleated Filter Cartridges dedicated to precision working conditions. It is defined as the filter cartridge achieving nearly 100% retention of contaminants at the rated particle size under standardized rigorous test conditions.

Compared with nominal rating, absolute rating allows zero testing tolerance and delivers full-area filtration without dead zones, fundamentally preventing penetration of rated-size contaminants. It maintains consistent filtration precision under long-duration operation and high-flow impact conditions, with no precision degradation or particle leakage.

Pleated filter cartridges with absolute rating adopt precision pleating technology with evenly and densely arranged filter media and superior raw materials. They are specially engineered for precision processes requiring strict fluid purity standards, such as pure water production, pharmaceutical, chemical and electronics manufacturing.

02. Nominal Rating vs Absolute Rating for Small Pleated Filter Cartridges

To help you clearly distinguish between the two, we conduct a comprehensive comparison of the two filter cartridges from four core dimensions: test standards, particle retention performance, structural manufacturing process, and cost & price.

1. Test Standards: Lenient Nominal Test vs Rigorous Traceable Test

Nominal Rating It adopts simple one-off static testing with loose test conditions and simplified inspection procedures. It only meets basic industrial nominal requirements, and the generated data offers limited reference value, failing to fully adapt to complex industrial working conditions.

Absolute Rating It strictly complies with ISO industrial standards and adopts multi-pass continuous dynamic testing to simulate real industrial scenarios with high flow rates and long-hour operation. All test data can be monitored and traced throughout the process, and the test results fully match the actual filtration performance under on-site working conditions.

2. Retention Performance: Fluctuating Precision vs Consistent & Accurate Precision

Nominal Rating Its particle retention efficiency is limited. Filtration performance is acceptable under static low-flow conditions. However, under high-flow impact or prolonged continuous operation, the pores of the filter medium are easily disturbed by water flow, leading to frequent particle penetration and severe fluctuations in filtration precision. It cannot guarantee stable fluid purity.

Absolute Rating It accurately intercepts all solid contaminants of the rated particle size and larger sizes. Featuring a stable filter medium structure, it delivers strong resistance to water flow impact. It maintains constant filtration precision even under 24-hour continuous operation and high-flow high-pressure conditions, eliminating the risk of particle leakage.

3. Structural Manufacturing Process: Mass-Produced Standard Design vs Precision Custom Design

Pleated Filter Cartridges with Nominal Rating Manufactured with general pleating technology, their filter membranes have mediocre pore uniformity. The pleat count and packing density follow standardized mass-production designs, leaving minor filtration dead zones. Raw materials are selected primarily for cost performance to satisfy basic filtration demands only.

Pleated Filter Cartridges with Absolute Rating Fabricated with precision balanced pleating technology, they feature strictly controlled medium spacing and pleat density, as well as uniform and dense membrane pores that completely eliminate filtration dead zones. High-purity premium filter media are adopted, with far superior consistency and stability compared to standard filters. Filtration precision is guaranteed through both advanced craftsmanship and premium raw materials.

4. Cost & Price: Cost-Effective vs High-Quality with Higher Cost

Nominal Rating Simple manufacturing processes, low raw material costs and high mass-production efficiency bring an affordable unit price. Suitable for bulk purchasing, it effectively cuts enterprises' filtration operation and maintenance expenses. Absolute Rating It requires strict raw material screening, elaborate precision production, and complicated inspection procedures with extremely high yield standards, resulting in higher overall production costs and a higher unit price than nominal rating filters. It targets mandatory filtration scenarios that demand ultra-high precision and outstanding stability.

03. How to Select the Proper Filter Rating

1. Scenarios Where Nominal Rating Pleated Filter Cartridges Are Preferred

These applications have low requirements for fluid purity and allow trace residual contaminants, with core demands of basic filtration and controllable costs:

● Wastewater pretreatment, general cooling water and washing water filtration

● Mass-consumption basic filtration processes with tight procurement budget control

● Coarse filtration for industrial pretreatment, tap water filtration, factory circulating water filtration

● Working conditions without strict standards for final water/fluid purity, only requiring removal of large-particle impurities

For the above basic pretreatment applications, Hongtek PCF Series Nominal PP Pleated Filter Cartridges are recommended. The full series adopts food-grade polypropylene filter media and is manufactured in clean workshops. Its multi-layer pleated structure delivers a large filtration area with lower pressure drop and higher dirt holding capacity. The cartridge adopts thermal welding glue-free sealing to prevent bypass leakage. Customization options include multiple ratings from 0.1 to 60 μm, lengths ranging from 5 to 40 inches, as well as various end caps and gaskets. It fits a wide range of pre-filtration applications such as RO pre-treatment, daily chemical, chemical and oil filtration, balancing stable filtration performance and cost advantages for bulk orders.

2. Scenarios Mandating Absolute Rating Pleated Filter Cartridges

These applications allow zero tolerance for contaminants; even trace particle penetration will cause product rejection or equipment failure, so absolute rating filter cartridges are compulsory:

● Final precision filtration for pure water and ultrapure water production

● Filtration of pharmaceutical liquids, biological preparations and cosmetic raw material fluids

● Filtration for precision electronics, semiconductors and high-purity chemical raw materials

● Final finished fluid filtration for critical processes requiring 100% product yield and purity

● Cartridge safety filtration upstream of RO and ultrafiltration membranes to protect downstream precision equipment

Hongtek APC Series Absolute Rating PP Pleated Filter Cartridges are the top choice for high-purity precision manufacturing processes. The products pass full integrity testing and meet the Beta 5000 standard, delivering an ultra-high particle retention rate of 99.98%. A 10-inch cartridge provides a filtration area up to 6.5 square feet. It withstands repeated high-temperature steam sterilization. Constructed entirely of polypropylene, it complies with FDA standards for food and pharmaceutical use and resists corrosion by various acid and alkaline solvents. An optional stainless steel inner core enhances stability under high operating pressure. It is suitable for particle-free critical processes including semiconductor manufacturing, pharmaceutical production and terminal pure water treatment, eliminating production losses caused by trace particle penetration at the source.

04. Common Misconceptions in Filter Rating Selection

Misconception 1: Judging solely by micron rating and assuming identical performance for cartridges with the same micron value

This is the most prevalent misunderstanding. The micron figure only indicates the rated particle size of a filter cartridge, rather than its actual filtration capacity. A 1 μm nominal rating cartridge and a 1 μm absolute rating cartridge have vastly different filtration precision and cannot be treated equally. Simply comparing micron parameters alone is meaningless.

Misconception 2: Improper use of nominal rating cartridges in precision processes, creating hidden production risks

To cut costs, many enterprises adopt nominal rating cartridges for critical processes such as pharmaceutical liquid filtration, terminal ultrapure water treatment and electronic raw material filtration. Although this seemingly reduces filter procurement expenses, trace particle penetration will lead to defective finished products, full batch rejection, or even clogging of downstream precision equipment, resulting in far greater economic losses.

Misconception 3: Over-specification for general working conditions, leading to unnecessary cost waste

Some buyers blindly select high-priced absolute rating cartridges for low-demand applications including pretreatment coarse filtration and conventional water circulation just to pursue "absolute safety". The high-precision performance is completely redundant. Long-term bulk consumption will drastically raise corporate operation and maintenance costs and create unnecessary resource waste.

Correct Selection Principle

Prioritize the precision requirements of working conditions. Adopt absolute rating cartridges for critical processes with strict precision standards, and nominal rating cartridges for basic filtration to balance costs. Matching filter ratings accurately to actual application demands delivers the most cost-effective solution.

Summary

Nominal rating filters stand out for cost-effectiveness, suited for basic filtration applications to meet routine particle removal demands. Absolute rating filters excel at ultra-precise and stable filtration, safeguarding fluid purity for precision manufacturing. Neither type is inherently superior; the difference lies solely in suitability for your working conditions.Feel free to consult us if you have specific filtration conditions, water quality parameters or equipment requirements. We offer customized precise selection solutions for pleated filter cartridges and professional filter rating testing consultation services to fully support your production filtration system.