ISO 12238:2023

Overview

ISO 12238:2023 - "Pneumatic fluid power - Directional control valves - Measurement of shifting time" defines standardized test procedures for measuring the shifting time of electrically or pneumatically operated directional control valves. The standard applies to monostable and bistable pneumatic directional control valves with 2‑position or 3‑position functions and clarifies how to record and report shifting on‑time and off‑time into exhausting, filling and non‑exhausting positions.

Key technical topics and requirements

• Definitions:
  • Shifting time (exhaust) - time for a 10% change in outlet pressure when shifting to an exhausting position.
  • Shifting time (fill) - time for a 10% change in outlet pressure when shifting to a filling position.
  • Shifting time (non‑exhausting) - measurement method when the working port is closed.
• Test equipment and setup:
  • Use straight pressure measuring tubes in accordance with ISO 6358‑1; transition connectors optional.
  • Install pressure transducers at inlet and each tested outlet port; plug untested ports.
  • For non‑exhausting positions use a throttle valve and flow sensor to generate measurable pressure change.
  • For pneumatically operated control, ensure the control valve sonic conductance exceeds that of the pilot port.
• Control signal and electrical requirements:
  • AC solenoids: trigger at zero‑voltage crossover; maintain voltage within ±2%.
  • DC solenoids: steady voltage within ±2%; negative‑peak limitations must not change shifting time by more than 0.1 ms.
  • Bistable valves: include a pause between actuations to exhaust pilot volumes before measuring reverse shifting time.
• Data acquisition:
  • System frequency response: –3 dB at ≥ 2 000 Hz (≥ 5 000 Hz for shifting times < 5 ms).
  • Time resolution: better than 0.1 ms.
  • Record control signal and pressure‑time diagrams for all transducers.
• Test accuracy and environmental limits:
  • Pressure ±10 kPa (±0.1 bar), temperature ±2 °C, time ±5%.
  • Supply reservoir temperature maintained between 18 °C and 30 °C; inlet pressure drop recommended ≤ 3% of supply.

Practical applications and users

• Who uses ISO 12238:2023:
  • Valve manufacturers validating product performance and catalog data.
  • Test laboratories and quality control teams performing repeatable, comparable shifting‑time measurements.
  • Pneumatic system designers and integrators specifying valve dynamic behavior for performance, safety and cycle‑time calculations.
  • R&D engineers benchmarking actuator and valve response for control system tuning.
• Benefits:
  • Produces repeatable, comparable measurements for product selection and compliance.
  • Helps predict system response, optimize cycle times and diagnose sources of delay in pneumatic circuits.

Related standards

• ISO 6358‑1 - Pneumatic flow measurement (pressure measuring tube requirements).
• ISO 1219‑1 - Graphical symbols for fluid power.
• ISO 5598 - Fluid power vocabulary.
• ISO 80000‑1 - Quantities and units.

For implementation details, test procedures, tables and example data consult the full ISO 12238:2023 document.