ISO 7233:2021

Overview

ISO 7233:2021 specifies test methods to determine the resistance to vacuum of rubber and plastics hoses and hose assemblies. The standard defines three test methods (A, B and C), the applicable hose dimensions for each method, required apparatus, specimen preparation and conditioning, test pressures and durations, inspection criteria, and required test-report contents. Its purpose is to verify that hoses will withstand differential pressure caused by reduced internal pressure in service and to detect internal defects such as delamination.

Key topics and requirements

• Scope of methods
  • Method A: for hoses of nominal size up to and including 80. Also used to detect lining/reinforcement delamination in hard-wall hose by observing the travel of an internal ball.
  • Method B: for hoses of nominal size greater than 80; uses transparent end plates for internal visual inspection.
  • Method C: applicable to all hose dimensions; may be used as an alternative to A and B where product standards do not specify a method.
• Apparatus
  • Vacuum pump with gauge capable of reducing internal pressure to the specified value within 60 s and maintaining it for ≥10 min.
  • Method A: smooth solid ball with diameter = 0.9 × bore (rounded down to nearest mm).
  • Method B: two transparent airtight plates, one permitting visual inspection and pump attachment.
• Specimens and conditioning
  • Test pieces: minimum 1 m of hose clear of fittings (or whole hose if <1 m).
  • No testing within 24 h of manufacture. Condition test pieces at the required temperature per ISO 23529 for at least 3 h before testing.
• Test procedure and measurements
  • Reduce pressure within 60 s to the internal test pressure specified in the product standard (or agreed value) and hold for a minimum of 10 min.
  • Method C requires marking measurement lines, and recording temporary and permanent changes in length and minor axis (outside diameter) before, during and after vacuum. Methods A and B emphasize internal/external visual inspection for collapse, blistering or delamination.
• Test report
  • Report must include ISO reference (ISO 7233:2021), full hose description, method used, internal test pressure (kPa/bar absolute), test duration, observations (collapse, delamination, ball traversal), percentage changes if method C used, deviations and test date.

Applications and users

• Manufacturers and quality engineers verifying product performance against vacuum service conditions.
• Independent test laboratories performing conformity and R&D testing.
• Product designers and R&D teams developing hose constructions resistant to collapse or delamination.
• Purchasers and specifiers seeking compliance evidence for hose assemblies used in vacuum or low-pressure systems (chemical transfer, suction lines, HVAC, industrial vacuum systems).

Related standards

• ISO 1402 - Hydrostatic testing of rubber and plastics hoses and hose assemblies (referenced for marking in Method C).
• ISO 8330 - Vocabulary for rubber and plastics hoses and hose assemblies.
• ISO 23529 - Conditioning procedures for rubber test pieces.

Keywords: ISO 7233:2021, resistance to vacuum, vacuum testing, rubber and plastics hoses, hose assemblies, method A B C, delamination, test procedure, test report, conditioning.