ISO 6773:1994

Overview

ISO 6773:1994 - "Aerospace - Fluid systems - Thermal shock testing of piping and fittings" defines an environmental test method for evaluating the resistance of aerospace fluid system piping and fittings (excluding hoses and hose assemblies) to thermal shock. This second edition (1994) cancels and replaces the first edition (1982). The standard ensures components can withstand rapid temperature and pressure changes without leaking or bursting under service-class pressures referenced to ISO 6772.

Key topics and requirements

• Scope: Applies to piping and fittings in aerospace fluid systems; explicitly excludes hoses and hose assemblies.
• Test fluid: Must be a system or hydraulic fluid compatible with the item under test and the specified system pressure/temperature.
• Test apparatus: Components include a temperature chamber, heat exchanger, pressure source (pump), valves, manometers and test fixture to mount assemblies. Graphic symbols conform to ISO 1219-1.
• Hot chamber procedure:
  • Pressurize assemblies to at least nominal circuit service pressure.
  • Raise chamber to at least the maximum specified circuit temperature and hold for minimum 2 hours.
  • While at temperature, replace hot fluid with cold fluid (initially at or below the minimum specified temperature) within 20 s.
  • Within an additional 20 s, raise pressure to at least the proof pressure, maintain for 1 minute, release for 1 minute, then repeat the 1-minute pressurization.
  • Observe continuously for leakage during pressurization periods.
• Cold chamber procedure:
  • After cooling to room temperature, pressurize and lower chamber to at least the minimum specified temperature, hold 2 hours.
  • Replace cold fluid with hot fluid within 20 s, apply proof pressure within the next 20 s, maintain 1 minute and observe for leakage.
• Test schedule: Repeat the hot-and-cold sequence three times.
• Acceptance: Test assemblies shall not leak or burst during the temperature and pressure cycling.

Applications and users

ISO 6773 is used by:

• Aerospace component manufacturers and suppliers (piping, fittings).
• Test laboratories and certification bodies performing environmental qualification.
• Aircraft systems engineers, quality assurance teams, and maintenance organizations validating hydraulic/fluid-system reliability. Practical uses include qualification testing during design validation, material selection, production verification and certification for aerospace hydraulic and fluid circuits subjected to rapid thermal transients.

Related standards

• ISO 6772:1988 - referenced for circuit pressure classification (pulse testing of hoses, tubing and fittings assemblies).
• ISO 1219-1 - graphic symbols for fluid power systems and components.

Keywords: ISO 6773, thermal shock testing, aerospace fluid systems, piping and fittings, hydraulic systems, environmental test method, proof pressure, thermal cycling.