Overview
ISO 18471:2015 specifies a laboratory test method for verification of filtration grade of filters used in agricultural irrigation systems. The standard defines how to use a Clogging Capacity Meter (CCM) to compare a filter under test against a calibrated test filtration screen and to confirm a filter manufacturer’s declared filtration grade (expressed in micrometres, μm). The method can also be used by manufacturers to determine filtration grade.
Key topics and technical requirements
- Test principle: Two CCM units (upstream and downstream of the test filter) run simultaneously. Each CCM uses a defined test screen and the time to reach a specified pressure loss is recorded.
- CCM components: Sampler (screen housing, replaceable filtering screen, flow regulator) and control unit (pressure gauges, differential pressure gauge, count-up timer with 0.01 min resolution).
- Operating parameters:
- CCM flow rate: 10 l/min (flow regulator accuracy ±2 %).
- Target pressure loss for timing: 0.5 bar across each CCM test screen.
- Pressure measurement accuracy: ±1 %; flow accuracy: ±2 %.
- Pass criterion: Calculate the ratio t_down / t_up (time for downstream CCM divided by time for upstream CCM). An average ratio ≥ 5 (from ten repetitions) indicates the declared filtration grade is correct.
- Test screens: CCM test screens are 316 stainless steel, plain-woven square mesh. The standard provides a table of typical aperture widths (range approximately 60 μm to 300 μm) and corresponding mesh/wire specifications.
- Procedure highlights:
- Adjust system inlet pressure (initially 4.0 bar, then 3.0–4.0 bar for testing) and set the filter flow to the midpoint of the manufacturer’s declared range.
- Record initial clean-filter pressure loss, replace filter medium with new identical medium before testing, and monitor during test.
- Abort conditions: filter pressure loss increases by 0.5 bar over the clean state; special discontinuation guidance if results are extremely fast or slow.
Applications and users
ISO 18471:2015 is intended for:
- Filter manufacturers verifying or determining declared filtration grades.
- Independent test laboratories performing conformity verification and quality control.
- Irrigation equipment specifiers and purchasers who need validated filtration performance data for system design.
- Certification bodies and agricultural OEMs requiring standardized, repeatable verification of filter performance.
Practical benefits include consistent, repeatable verification of particle retention characteristics to protect emitters, nozzles and downstream irrigation components.
Related standards
- ISO 9644 - Pressure losses in irrigation valves (test method) (normative reference for pressure taps)
- ISO 9045 - Industrial screens and screening - Vocabulary
- ISO 80000-1 - Quantities and units (units used in standard)
Keywords: ISO 18471:2015, filtration grade, Clogging Capacity Meter, CCM, agricultural irrigation filters, verification of filtration grade, test method, filtration screens, pressure loss, flow rate.