Overview
ISO 6556:2012 - Laboratory glassware - Filter flasks - specifies design, material and test requirements for filter flasks used for general laboratory vacuum filtration. The standard covers both conical and cylindrical flask shapes, defines two product series (A and B) with specific nominal capacities, and sets requirements for material (borosilicate glass 3.3), mechanical strength and thermal performance.
Key topics and technical requirements
- Material: Filter flasks shall be made of borosilicate glass 3.3 (ISO 3585) and be free from residual strain or defects likely to impair safety or durability.
- Shapes and series:
- Series A: Conical (100 ml, 250 ml, 500 ml, 1 000 ml, 2 000 ml) and cylindrical (3 l, 5 l, 10 l, 15 l, 20 l).
- Series B: Conical only (25 ml, 50 ml, 125 ml, 250 ml, 500 ml, 1 000 ml, 2 000 ml, 4 000 ml).
- Vacuum connections:
- Series A: tubular side-arm (taper 1:5 to 1:10), integral side-arm with glass round thread, or detachable side-arm (with grommet or threaded connector).
- Series B: connections placed near neck-to-body junction and can be plain, tubular (corrugated, tapered or with round thread) or replaceable (straight/angled/multiple).
- Mechanical strength: Flasks must withstand an external-internal pressure differential of 2 bar (type tested per Annex A). Dimensions for minimum wall thickness and base radius are specified in the standard tables to ensure pressure resistance.
- Thermal shock endurance: Type tested to endure 75 °C thermal shock in accordance with ISO 718.
- Construction details: Requirements for neck design (may accept interchangeable joints per ISO 383), base radius to prevent rocking, and optional external protective plastic coating.
- Marking: Permanent legible inscriptions of nominal capacity, maker/vendor name or mark, and glass type (if not identified by maker).
Applications and users
- Practical for laboratories performing vacuum filtration, microbiology, environmental testing, and chemical analysis where reliable vacuum-resistant glassware is required.
- Primary users: laboratory managers, glassware manufacturers, quality managers, procurement officers, and safety officers who need compliance/selection criteria for filter flasks.
- Also used by test labs and regulatory/standards bodies to verify product conformance to mechanical and thermal tests.
Related standards
- ISO 3585 - Borosilicate glass 3.3 - Properties
- ISO 718 - Thermal shock and thermal shock endurance - Test methods
- ISO 383 - Interchangeable conical ground joints
Keywords: ISO 6556, filter flasks, laboratory glassware, borosilicate glass, vacuum connection, pressure strength, thermal shock endurance, Series A, Series B.
