ISO 6772:2012

Overview

ISO 6772:2012 specifies requirements and procedures for impulse testing of hose, tubing and fitting assemblies used in aerospace hydraulic (and, where appropriate, other aerospace fluid) systems. The standard provides a repeatable test method to evaluate assembly resistance to hydraulic impulse fatigue and to support qualification and evaluation of components for system use.

The standard emphasizes traceable measurements, controlled pressure-waveform shape and repeatable test sequences to demonstrate long-term reliability under simulated service conditions.

Key Topics

• Impulse trace shape: Dynamic pressure/time traces observed on an oscilloscope must conform to the specified envelope (the shaded area in the standard) and permit assessment of rate-of-rise and peak characteristics.

• Rate of pressure rise: Calculated from the times at 10 % and 90 % of peak pressure using the formula:

  Rate of pressure rise = (0.9·p - 0.1·p) / (t_at_0.9p - t_at_0.1p)

  where p is the peak pressure and t_at_0.9p / t_at_0.1p are the corresponding times.

• Peak pressure and classes: Peak pressures and required minimum/maximum rates of rise are specified by pressure class and nominal diameter in Tables 1 and 2.

• Specimen preparation: Test specimens must follow the component detailed design specification and receive applicable production treatments and production tests prior to impulse testing.

• Test fluid: The test fluid shall be the specified aircraft system fluid or another hydraulic fluid compatible with the component under test.

• Test method and duration: Typical cycle rate is (70 ± 5) cycles/min and, unless otherwise specified, the total number of cycles is 200 000. Oscilloscope sweep and data acquisition must record the impulse trace with accuracy traceable to international standards.

• Temperature and soak: Temperature sequences and soak times are defined (see Table 3); a minimum 1 h soak is required after stabilizing at maximum or minimum temperatures before testing that portion of the sequence.

Applications

ISO 6772:2012 is used by:

• Manufacturers for qualification testing of hydraulic hose assemblies, tubing and fittings.
• Test laboratories validating component endurance against hydraulic impulse fatigue.
• Procurement and design teams to specify standardised impulse-test requirements and acceptance criteria.

Benefits include improved reliability of fluid transmission elements, standardized test reporting, and evidence of fatigue resistance for certification and procurement.

Related Standards

• ISO 6771 - Pressure and temperature classifications (referenced for pressure classes).
• ISO 8575 - Hydraulic system tubing (referenced for nominal outside diameters).
• ISO 8625-1 - Vocabulary for pressure-related terms (definition of peak pressure).
• SAE AIR 1228 - Standard Impulse Machine Equipment and Operation (bibliographic reference).

For implementation, refer directly to ISO 6772:2012 for tables, figures and exact test envelopes and procurement-specific requirements.