Overview
ISO 19973-2:2015 - "Pneumatic fluid power - Assessment of component reliability by testing - Part 2: Directional control valves" specifies test procedures, equipment and reporting methods for assessing the reliability of pneumatic and electro-pneumatic directional control valves. It complements ISO 19973-1 (general procedures) and defines how lifetime is expressed (cycles), how the three-points moving average (3PMA) method is applied to determine first failure (without repairs, excluding outliers), and the threshold levels used to judge failures.
Key Topics and Requirements
- Scope and lifetime unit: Lifetime is expressed in cycles; whenever the standard uses “time” it means cycles.
- Test equipment: Basic circuits for testing two-position (bi-stable and mono‑stable) and three‑position valves, rules for silencers, pilot supply and safety considerations.
- Connecting piping and volumes: Guidance to avoid flow restrictions; keep tubing short so volumes charge/vent within control-signal timing.
- Test conditions: Initial functional checks; cycling requirements (outlet pressures must fall below 10% and rise above 90% of supply during a cycle); actuation on/off ratio 1:1.
- Control signals: Defined patterns for mono‑stable and bi‑stable/three‑position valves to ensure reproducible cycling.
- Checks and measurements:
- Functional checks (acoustic, visual, tactile) to detect switching failures or incomplete charging.
- Leakage measurements (functional leakage and specific internal/external pilot leak checks depending on valve type).
- Measurement of shifting pressures (performance change over cycles).
- Failure criteria and thresholds: Criteria for functional failure, leakage failure and shifting-pressure failure; customizable agreements allowed between parties.
- Data analysis and reporting: Use methods from ISO 19973-1 for statistical analysis and prepare a standardized test report.
Applications and Users
ISO 19973-2:2015 is intended for:
- Valve manufacturers - for design validation, production testing and reliability claims.
- Test laboratories and OEMs (machine builders) - to evaluate component reliability, set maintenance intervals, and optimize spare-part inventories.
- Reliability and quality engineers - for reliability modelling, warranty analysis and continuous improvement.
Practical uses include predicting valve lifetime in cycles, establishing service schedules, and informing FMEA, design changes and production acceptance tests.
Related Standards
Keywords: ISO 19973-2:2015, pneumatic directional control valves, reliability testing, 3PMA, leakage measurement, cycling frequencies, test procedures, threshold levels.