Quick Summary
As power densities in modern data centers rise, maintaining steady thermal performance in evaporative and water-assisted cooling systems becomes critical. Suspended solids in cooling loops can foul plate heat exchangers, degrade heat transfer efficiency, and impact Power Usage Effectiveness (PUE).
Specifying filtration systems based on unverified “nominal micron ratings” introduces operational risks, as nominal ratings alone do not standardize capture efficiency under variable suspended-solid loads. To ensure filtration accuracy, facility designers look to standardized testing methods such as ISO 18471, which objectively evaluates a filter’s declared filtration grade against a reference screen. Amiad’s DATA Klin, powered by patented Spin Klin™ NOVA 3D depth disc technology, provides ISO 18471-verified 55-micron filtration to support reliable side-stream cooling operations.
What You Will Learn:
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The Operational Risks of Unverified Filtration in Data Center Operations
In modern data center operations, maintaining stable heat transfer across cooling-loop heat exchangers is critical to reliable cooling performance.
When cooling towers introduce airborne dust, pollen, and debris into the recirculating water loop, inadequate particulate control can create several operational challenges:
- Thermal Resistance: Suspended solids can accumulate on heat-transfer surfaces, reducing heat-transfer efficiency.
- Energy Impact: Fouling can increase the energy required by pumps and chillers to maintain cooling performance.
- Nominal Rating Uncertainty: An unverified nominal micron rating does not indicate how the declared filtration grade was established or verified under standardized test conditions.
For mission-critical cooling systems, standardized verification provides a more reliable basis for evaluating declared filtration performance.
Understanding ISO 18471: Standardized Verification for Filtration Grade
Although ISO 18471 (Agricultural irrigation equipment – Filters – Verification of filtration grade) was developed for filters used in agricultural irrigation systems, its standardized methodology provides a consistent, objective framework for verifying a manufacturer’s declared filtration grade. Amiad applies this verification methodology to its Spin Klin™ disc filtration technology.
ISO 18471 uses a specialized testing apparatus known as a Clogging Capacity Meter (CCM) to compare the filtration grade and particle-retention behavior of the filter under test with that of a high-precision reference filtration screen.
Verified Clogging Performance
The testing protocol evaluates the degree of clogging on the downstream reference screen relative to the test filter under controlled suspended-solid loading.
- The Standard Threshold: To satisfy the verification criteria, a filter must achieve a filtrate clogging ratio well above the minimum standard threshold of 5.0.
- Amiad Spin Klin™ Results: In laboratory testing in accordance with ISO 18471 criteria, Amiad’s Spin Klin™ disc technology demonstrated a filtrate clogging ratio of 16 at 55 µm and 15 at 100 µm, confirming high particle retention well above the standard’s minimum requirement.
By evaluating performance under standardized testing, ISO 18471 provides facility engineers with standardized, reproducible verification data that declared filtration ratings reflect consistent particulate capture.
Different Filtration Mechanisms and Their Performance Characteristics
Evaluating physical side-stream filtration options requires understanding the mechanical capture mechanisms of different technologies under variable solids loading:
- Surface Screen Filters: Screen filters provide direct, two-dimensional surface filtration. They are effective for removing rigid inorganic particulates. Automatic screen filters utilize mechanical self-cleaning mechanisms that allow continuous operation without interrupting main system flow.
- Centrifugal Separators (Hydrocyclones): Centrifugal separators rely on fluid velocity and density differentials to separate solids from water. They are particularly effective for capturing large, dense inorganic particles such as sand and grit . Because separation depends on specific gravity, performance varies with particle density, size, and shape, making them less suited for lightweight organic matter with densities close to water.
- Polymeric Disc Filters (Depth Filtration): Disc filters utilize stacks of grooved polymeric discs compressed tightly along a central spine. They provide three-dimensional depth filtration that captures both dense particulates and lightweight organic matter (such as airborne pollen and algae) throughout the depth of the grooved disc channels .
The Spin Klin™ NOVA Advantage: ISO 18471-Verified 3D Depth Filtration
Amiad’s DATA Klin series utilizes patented Spin Klin™ NOVA polymeric disc technology, verified in accordance with ISO 18471 methodology.
Key Operating Characteristics:
- Three-Dimensional Particle Retention: Water flows through the compressed cross-grooved matrix, capturing particles at multiple intersection points throughout the depth of the disc stack, rated to 55 microns as standard.
- Verified Retention Performance: In the ISO 18471 test results reported by Amiad, Spin Klin™ disc technology exceeded the required performance threshold at both 55 and 100 microns.
- Continuous Side-Stream Operation: The DATA Klin operates on an active side-stream loop. Side-stream filtration systems are generally sized to filter 3% to 10% (up to 20%) of the overall system flow. During automatic self-cleaning cycles, individual disc pods backwash sequentially in seconds using minimal water, maintaining uninterrupted cooling flow to the facility.
- Polymeric Corrosion Resistance: Spin Klin™ NOVA’s polymeric disc filtration components provide high corrosion resistance for demanding cooling-water environments.
Parallel Industrial Applications: Reliable Filtration Under Heavy Solids Loads
Amiad’s filtration technologies have been deployed across demanding industrial cooling applications requiring consistent particle removal.
Note: These parallel industrial applications demonstrate relevant filtration principles in heavy cooling environments; they are not data center installations.
Cooling Tower Side-Stream Filtration (Oil & Gas Facility, USA)
A major petroleum refining and gas processing facility in the United States experienced ongoing cooling-tower basin sedimentation caused by atmospheric grit and airborne debris. Particulate accumulation created maintenance challenges and increased blowdown requirements. The facility installed an Amiad automated filtration package on a side-stream configuration. The side-stream system reduced the maintenance burden associated with cooling-tower contamination and allowed the cooling tower to operate with little filter-related maintenance or service labor after installation.
High-Salinity Cooling Filtration (Thermoelectric Power Plant, Chile)
A large power generation plant in Chile utilized raw seawater for condenser cooling, an aggressive, high-solids environment. Existing metallic screen filters experienced severe corrosion and frequent operational issues. The plant replaced the failing equipment with an Amiad Spin Klin™ Galaxy polymeric disc filtration system operating at 100 microns. The polymeric disc system delivered continuous depth filtration while resisting the corrosive effects of the saline water, demonstrating the operational durability of polymer disc construction under heavy, corrosive cooling loads.
Conclusion
As data center cooling infrastructures face higher thermal densities, relying on unverified filtration specifications introduces unnecessary operational risks to critical cooling loops.
By specifying filtration systems verified under standardized testing protocols such as ISO 18471, data center operators can rely on a standardized, reproducible framework for verifying declared filtration grades. Implementing proven 3D depth disc filtration, such as Amiad’s DATA Klin, helps control suspended solids, protect plate heat exchangers from fouling, and support long-term operational resilience in demanding data center environments.
A Call for a Purpose-Built Standard
ISO 18471 originated within agricultural irrigation, which remains a recognized limitation when applying the protocol to mission-critical data center cooling. However, until a dedicated filtration-grade verification standard is established for data centers, ISO 18471’s Clogging Capacity Meter methodology provides the most rigorous, reproducible protocol for evaluating declared filtration claims.
As thermal densities rise across AI-driven campuses, industry bodies such as ASHRAE, ASTM, OCP, the Cooling Technology Institute, and Uptime Institute are uniquely positioned to help close this standards gap.
Until a dedicated data center standard exists, specifiers should treat standardized, reproducible verification data as a baseline requirement. As direct-to-chip cooling pushes toward increasingly restrictive flow paths, the margin for uncertainty in filtration performance disappears.
FAQ About ISO 18471 and Data Center Filtration
What is the main difference between a nominal rating and an ISO 18471 verified rating?
A declared nominal rating indicates the filtration grade claimed for a filter without standardizing how that grade was evaluated under active solids loading. An ISO 18471 verified rating confirms that a filter’s declared filtration grade has been evaluated against a reference screen using a standardized laboratory testing protocol.
How does three-dimensional disc filtration differ from a standard surface screen?
A standard surface screen captures particles on a two-dimensional mesh face. Grooved polymeric discs, when compressed, form a three-dimensional depth matrix with multiple intersection points, trapping particulates and organic debris throughout the full depth of the disc stack.
Why is side-stream filtration preferred over full-flow filtration for cooling towers?
Full-flow filtration requires sizing equipment for 100% of the cooling loop, resulting in larger equipment footprints, higher capital costs, and greater energy consumption. Side-stream filtration continuously treats a fraction (typically 5% to 15%) of the circulating flow, which effectively controls suspended solids and maintains basin cleanliness with a smaller footprint and lower capital requirements.
