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D1831-21 – Standard Test Method Technical Guide
🧪 Scope and Application of D1831-21
This standard test method covers the determination of changes in the consistency, as measured by cone penetration, of lubricating greases when worked in the roll stability test apparatus. As specified in Section 1.2, values stated in SI units are to be regarded as standard, while any values given in parentheses are provided for information only. The standard relies on precise terminology established in Section 3 and directly references ASTM D217 and D1403 for measuring penetration across various sample scales.
📐 Referenced Standards and Measurement Scales
D1831-21 integrates two distinct penetration measurement scales depending on the sample available. ASTM D217 defines the standard cone and full-scale penetration method, while ASTM D1403 specifies the equipment for 1/4-scale and 1/2-scale cone tests. The standard explicitly warns that due to differences in apparatus geometry and cone mass, the terms “penetration” and “reduced-scale penetration” are not synonymous and should not be confused, even though both values are reported in units of 0.1 mm.
| ⚡ Referenced Standard | 📐 Application in D1831-21 |
|---|---|
| ASTM D217 | Defines the standard cone penetrometer, grease worker, and full-scale penetration procedure used to measure grease consistency before and after the roll stability test. |
| ASTM D1403 | Specifies the 1/4-scale and 1/2-scale cone equipment used for reduced-scale penetration and reduced-scale worked penetration measurement when sample quantity is limited. |
⚠️ Critical Scale Distinction: The penetration forces for reduced-scale cones are determined by the respective masses of the cones and shafts. Therefore, reduced-scale penetration values (Section 3.1.5) are not directly interchangeable with full-scale penetration values (Section 3.1.4).
📊 Key Terminology and Measured Properties
The technical rigor of D1831-21 is grounded in its detailed definitions. The lubricating grease is described as a two-phase system of a thickener dispersed in a