Overview
ISO 6358-1:2013/Amd 2:2026 is an important international standard from the International Organization for Standardization (ISO) covering pneumatic fluid power systems. This amendment focuses on the evaluation of measurement uncertainty in the determination of flow-rate characteristics of components using compressible fluids. The standard provides general rules and test methods for steady-state flow and now, with Amendment 2, offers updated and practical guidance on measurement uncertainty-critical for reliable and comparable test results in pneumatic applications.
By addressing uncertainty in the measurement of key parameters such as sonic conductance, critical back-pressure ratio, and subsonic index, this document helps manufacturers, laboratories, and test engineers ensure consistent and accurate evaluation of pneumatic components.
Key Topics
- Measurement Uncertainty Evaluation: The standard adopts methodologies aligned with ISO/IEC Guide 98-3 (GUM) for estimating uncertainty in the measurement of flow-characteristics, balancing rigor and practicality for industrial use.
- Uncertainty Components:
- Type A (Statistical): Estimated from repeat measurement data using statistical methods.
- Type B (Non-statistical): Estimated from external sources such as reference materials, calibration certificates, and environmental conditions.
- Combined Uncertainty Approach: Most measurements require combining Type A and Type B components, using propagation of uncertainty to yield comprehensive values.
- Sonic Conductance Calculation: The uncertainty in sonic conductance-an essential flow parameter for pneumatic components-is calculated through defined formulas and the averaging of multiple data sets in choked flow conditions.
- Critical Back-Pressure Ratio and Subsonic Index: These parameters capture additional aspects of flow performance, with uncertainty evaluated through practical limits based on experimental standard deviations.
- Maximum Measurement Bias: The standard addresses the effect of upstream stagnation pressure measurement and provides tabulated maximum potential bias values for various component and connector sizes, emphasizing best practices for minimizing systematic error.
Applications
- Component Testing: Ensures test laboratories can reliably assess the flow-rate characteristics of pneumatic valves, actuators, fittings, and other components.
- Quality Control: Provides manufacturers with standardized methods to validate product performance and maintain consistent quality in production batches.
- Product Development: Engineers can use these uncertainty evaluation techniques during design verification and pre-compliance testing to optimize pneumatic component reliability.
- International Trade: Harmonized and reproducible test results facilitate product acceptance in global markets by meeting recognized ISO standards.
- Accreditation and Compliance: Supports calibration laboratories and certification bodies in demonstrating conformity to international measurement uncertainty requirements.
Related Standards
- ISO 6358 Series: Includes additional parts covering specific test procedures and component types within pneumatic fluid power systems.
- ISO/IEC Guide 98-3 (GUM: 1995): International consensus for uncertainty in measurement, referenced throughout this amendment.
- ISO 6358-1:2013: The base document providing general rules and steady-state flow test methods for pneumatic components.
- Other ISO Fluid Power Standards: Refer to ISO/TC 131-related documents for broader fluid power system requirements.
For manufacturers, test engineers, and laboratories evaluating pneumatic components, ISO 6358-1:2013/Amd 2:2026 is essential for ensuring reliable measurement, comparability, and compliance with international best practices in measurement uncertainty. This amendment enhances the confidence and credibility of pneumatic flow-rate data worldwide.
Open preview (PDF)Pneumatic fluid power — Determination of flow-rate characteristics of components using compressible fluids — Part 1: General rules and test methods for steady-state flow — Amendment 2: Evaluation of measurement uncertainty
