ISO 9110-2:2020

Overview

ISO 9110-2:2020 - Hydraulic fluid power - Measurement techniques - Part 2 - defines standardized procedures for the measurement of average steady‑state pressure in a closed hydraulic conduit. It applies to closed conduits with inside diameters > 3 mm, average fluid velocities < 25 m/s, and steady‑state static pressures < 70 MPa. The document excludes flush‑mounted or integral conduit‑wall sensors and provides the formulae and guidance needed to estimate total measurement uncertainty.

Key topics and technical requirements

• Measuring instrument selection and calibration
  • Full calibration of uncalibrated instruments; calibration records and uncertainty models are required.
  • Consider readability uncertainty, thermal sensitivity, mounting orientation, and vibration isolation.
• Pressure tap types and installation
  • Defines three tap categories (Type 1, Type 2, Type 3) and geometric requirements for tap holes.
  • Placement rules: typically a minimum of 10d downstream from disturbances and 5d upstream, where d = inside diameter.
  • Only one tap used per measurement point; avoid low points where contamination collects.
• Uncertainty contributors
  • Provides formulae and methods to evaluate: velocity‑induced pressure uncertainty (different for tap types), tare pressure (pressure loss between taps), environmental effects (temperature, vibration, supply voltage), and fluid head corrections.
  • Recommends inclusion of maximum expected values as uncertainty contributors when corrections are impractical.
• Tare (baseline) pressure and flow effects
  • Procedures for determining tare pressure by removal of the test component or by using friction‑factor based calculations (Poiseuille for laminar, Blasius for turbulent flow) and experimental determination of f.
• Practical measurement procedure
  • Bleeding air from lines, instrument mounting, thermal control, and data correction practices.

Applications and who should use this standard

ISO 9110-2:2020 is intended for professionals involved in hydraulic test and measurement, including:

• Test engineers and laboratory technicians conducting component or system pressure testing
• Hydraulic system designers validating steady‑state pressure performance
• Quality managers and compliance officers ensuring repeatable pressure measurements
• Calibration laboratories that produce traceable pressure measurements for hydraulic systems
• Manufacturers of hydraulic components (pumps, valves, actuators) that require standardized pressure measurement procedures

Adoption improves repeatability, traceability, and confidence in pressure data used for performance evaluation, product development, and conformity assessment.

Related standards

• ISO 9110-1 - Hydraulic fluid power - Measurement techniques - Part 1: General measurement principles (to be used in conjunction)
• ISO 5598 - Fluid power systems and components - Vocabulary

Keywords: ISO 9110-2:2020, hydraulic fluid power, pressure measurement, average steady‑state pressure, pressure taps, measurement uncertainty, closed conduit, calibration, tare pressure.