Overview
ISO 2137:2020 - "Petroleum products and lubricants - Determination of cone penetration of lubricating greases and petrolatum" defines standardized laboratory methods to measure the consistency (cone penetration) of lubricating greases and petrolatum. The standard describes apparatus, sampling, test procedures and calculation rules for unworked, worked, prolonged-worked and block penetrations using a penetrometer and a standardized cone. Results are used to classify grease consistency (e.g., NLGI ranges) and to support quality control, formulation and specification.
Key topics and technical requirements
- Test principle: A standardized cone assembly is released onto a test portion at 25 °C and allowed to drop for 5 s; penetration depth (expressed in 0.1 mm units) is measured. Three determinations are averaged.
- Types of penetration measurements:
- Unworked penetration - minimum disturbance sample transfer.
- Worked penetration - after 60 double strokes in a standard grease worker.
- Prolonged worked penetration - after more than 60 strokes.
- Block penetration - measured on the face of a cut grease block.
- Petrolatum - melted, cooled under specified conditions, then tested as grease.
- Apparatus and scales: Full‑scale cone methods (Clause 8); one‑half and one‑quarter scale cone methods (Clause 9) for small samples, with conversion formulas to full‑scale values and stated limitations (one‑quarter-scale precision is limited).
- Sampling & preparation: References ISO 23572 for sampling of greases and details sample preparation and handling.
- Accuracy & reporting: Precision data (repeatability r and reproducibility R), calculation methods, expression of results and test report requirements are specified.
- Recent revisions: Includes guidance to clean cone and shaft assemblies with solvent to avoid drag forces and updated precision tables for scaled cones.
Applications and practical value
- Quality control: Routine lab testing to ensure grease consistency meets product specifications and NLGI classification.
- Product development: Formulators compare consistency changes due to thickeners, base oils and additives.
- Procurement & compliance: Suppliers and purchasers use cone penetration data as objective acceptance criteria.
- Failure analysis & field evaluation: Helps correlate grease consistency with performance in bearings, gears and other lubricated components.
- Lubricant manufacturers and formulators
- Petrochemical and tribology laboratories
- Quality assurance teams and test houses
- Industrial users specifying grease or petrolatum performance
Related standards
- ISO 23572 - Sampling of lubricating greases (normative reference)
- ISO 6743-99 / ISO 12924 - References for NLGI classification and grease categories
Keywords: ISO 2137:2020, cone penetration, lubricating greases, petrolatum, penetrometer, grease consistency, worked penetration, unworked penetration, NLGI classification.