ISO 9644:2018

Overview

ISO 9644:2018 specifies a standardized test method for measuring pressure losses in agricultural irrigation valves under steady-state water flow. Applicable to manually-activated valves with equal inlet and outlet nominal sizes, the standard defines the test installation, measurement requirements, calculation of valve performance coefficients, and the format for reporting test data. Its purpose is to help irrigation system designers, manufacturers and test laboratories compare pressure loss characteristics across valve types.

Key topics and technical requirements

• Scope: Manually‑activated irrigation valves; steady‑state flow; equal inlet/outlet nominal sizes.
• Test installation: Upstream and downstream piping must match valve connection diameter and include specified straight lengths and pressure‑tap locations. A downstream throttling valve controls flow.
• Measuring equipment & accuracy: Permissible deviations - flow ±2%, pressure ±2%, temperature ±1 °C. Flow meter location, pressure differential device and temperature sensors are specified.
• Pressure taps: Two taps for DN < 50 mm, four for DN ≥ 50 mm; tap diameter, bore length and placement requirements are defined to ensure accurate static pressure measurement.
• Test conditions: Defines steady vs. unsteady conditions, allowable fluctuations, minimum reading sets under varying instability and procedures for damping pulsations. Water temperature during tests should be 5 °C to 50 °C.
• Calculations & reporting: Procedures to determine valve flow coefficient (Kv or K_v) and flow resistance coefficient (ζ), bench pressure loss correction, and the required test report content.
• Uncertainty: Annex A and B provide guidance on measurement uncertainty and evaluation of uncertainty for flow and pressure‑loss coefficients.

Applications

• Irrigation system designers use ISO 9644:2018 data to size pumps, select valves and predict head losses for system modeling.
• Manufacturers apply the method for product performance characterization and quality control.
• Test laboratories and certification bodies adopt the standard to produce comparable, repeatable pressure‑loss data.
• Procurement and specification writers reference standardized Kv/ζ values to compare valve options objectively.

Related standards (if applicable)

• Complementary ISO and national standards on hydraulic testing, flow measurement and irrigation equipment provide broader context for valve testing and system design. Users should consult relevant ISO/TC 23 documents on irrigation and drainage equipment for additional guidance.

Using ISO 9644:2018 ensures consistent, reproducible pressure‑loss measurements for irrigation valves, enabling reliable hydraulic design and objective product comparisons.