Overview
ISO 7458:2004 - Glass containers - Internal pressure resistance - Test methods specifies standardized laboratory procedures to determine how glass containers withstand internal pressure. The standard defines two test methods: Method A (uniform internal pressure held for a predetermined time) and Method B (internal pressure increased at a constant, predetermined rate). The prescribed test medium is tap water and sampling must use a predetermined number of containers that have not been previously mechanically or thermally tested.
Key Topics and Requirements
- Test methods
- Method A (pressure-hold): apply internal pressure at an initial rate of (10 ± 2) bar/s (≈ 1.0 ± 0.2 MPa/s) and maintain the target pressure for (60 ± 2) s (or another agreed duration with correction to 60 s).
- Method A - progressive option: increase pressure in steps of 1 bar or 2 bar (0.1 or 0.2 MPa) to record first break, 50% or 100% failure points.
- Method B (ramp test): increase pressure continuously at (5.8 ± 1) bar/s (≈ 0.58 ± 0.1 MPa/s) until breakage or a preset level; the rate reproducibility must be ±2%.
- Apparatus
- Containers must be suspended by the ring and sealed with an elastic gasket between the sealing surface and pressure injector.
- Devices must display the pressure at which breakage occurred and, for Method B, the relationship to the 60 s pressure-hold test (a conversion relation is provided in the standard).
- Sampling and specimen condition
- Use a predetermined sample size; specimens must not have prior mechanical or thermal testing that could affect pressure resistance.
- Reporting
- Test reports must include standard reference (ISO 7458:2004), sample size, mold counts, test type, detailed results (pressures, number failed, first-break pressure, mean break pressure and standard deviation), date, location and responsible signature.
- Safety
- Tests can be hazardous; appropriate protective measures and test-enclosure practices are required.
Applications and Users
ISO 7458 is used for quality control, product development and compliance testing of glass containers where internal pressure resistance is critical. Typical users:
- Glass manufacturers and molding plants
- Independent testing laboratories and QA/QC teams
- Packaging engineers and product designers
- Regulatory and conformity-assessment bodies
Practical applications include assessing container performance under internal pressure conditions (e.g., pressure from carbonation, sterilization or thermal expansion) and establishing acceptance criteria for production batches.
Related Standards
ISO 7458:2004 is part of a series of glass test standards. Related documents include ISO 7459 (thermal shock resistance), ISO 8113 (vertical load resistance) and ISO 8106 (capacity determination). Refer to the ISO catalogue or national adoption texts for full cross-references.
