Overview
SIST 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