Overview
ISO 6247:1998 - Petroleum products: Determination of foaming characteristics of lubricating oils - specifies a laboratory method to measure the foaming tendency and foam stability of lubricating oils at defined moderate temperatures. The procedure is empirical and applicable to lubricants with or without antifoam additives. Results indicate potential lubrication, cavitation or performance problems in systems where foam formation can impair equipment operation.
Key topics and technical requirements
- Test principle: Air is passed through a sample at a controlled flow rate; foam volume is recorded after a 5-minute blowing period and after a 10-minute settling period. Tests are run at 24 °C and at 93.5 °C with a subsequent cool-down sequence.
- Main apparatus:
- 1 000 ml graduated cylinder (190 ml / 180 ml fill levels used in sequences)
- Spherical or cylindrical diffuser (fused alumina or sintered stainless steel)
- Flowmeter (set to 94 ml/min ± 5 ml/min) and a volume-measuring device (or simplified routine option)
- Temperature-controlled baths capable of ±0.5 °C
- Diffuser specification (Annex A):
- Maximum pore diameter: 80 µm
- Permeability: 3 000–6 000 ml/min (measured at 2.45 kPa)
- Annex A defines the test methods to verify pore diameter and permeability
- Sampling and sample preparation:
- Heating/cooling steps (eg. preheat to 49 °C then cool to 24 °C) and an optional high-speed agitation (Option A) for stored samples
- Cleaning procedures for cylinder and diffuser to avoid contamination
- Results and reporting:
- Report foaming tendency (foam volume at end of blowing) and foam stability (foam volume after settling), to the nearest 10 ml
- Include test sequence, sample identification, any deviations and date
- Precision: Interlaboratory-derived repeatability and reproducibility are provided in the standard (formulated as functions of mean value).
Applications and users
This standard is useful for:
- Lubricant manufacturers and formulators validating antifoam additives
- Quality-control and analytical laboratories performing routine acceptance testing
- Equipment OEMs and maintenance engineers assessing lubricant suitability for hydraulic systems, compressors and gearboxes where foam can cause cavitation, loss of lubrication or erratic operation
- R&D teams evaluating new formulations for foam performance
Practical value: ISO 6247:1998 provides a repeatable, documented foaming test that links laboratory measurements to field-relevant concerns (foam generation and persistence), helping users control product quality and reduce equipment risk.
Related standards
- ISO 3696:1987 - Water for analytical laboratory use (reference for water quality in this test)
- ISO 6353-2 and ISO 6353-3 - Reagents for chemical analysis (referenced reagent specifications)
- Annexes A and B of ISO 6247:1998 (normative) cover diffuser testing and temperature sensor requirements respectively
Keywords: ISO 6247:1998, foaming characteristics, lubricating oils, foaming tendency, foam stability, diffuser pore diameter, permeability, lubricant foam test.
