Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D441-07 – Standard Test Method Technical Guide
📐 Test Overview and Significance
ASTM D441-07 provides a standardized method for determining the relative friability of sized coal. Friability refers to the coal’s tendency to break into smaller pieces due to handling, which is critical for assessing quality during mining, transport, and use. This test method measures the liability of coal to break when subjected to repeated handling, making it valuable for comparing coals for similarity rather than assigning precise values. It can also indicate size degradation in mechanical feed devices and assist in coal classification by differentiating between ranks and grades.
The standard specifies that values are stated in inch-pound units, with mass optionally in metric values. It is developed in accordance with international standardization principles and does not address all safety concerns, requiring users to establish appropriate practices.
🛠️ Apparatus Construction and Dimensions
The apparatus consists of a cylindrical porcelain jar tumbler with uniform internal dimensions of 71/4 inches in both diameter and depth. The jar is fitted with an iron frame that includes two rings and three lifting shelves. The rings have an outside diameter of 71/8 inches and are made from 3/4 inch by 1/8 inch iron. The shelves are 61/2 inches long, 3/4 inch wide, and 1/8 inch thick, attached radially to the rings with small brackets. There is a clearance of 5/8 inch between the outer edge of the shelves and the outside of the rings. The frame must be constructed using rivets, not bolts, and is fixed inside the jar with wedges to ensure coaxial alignment. The jar is closed with a set-in porcelain lid on a heavy rubber gasket.
| 🟦 Component | 📏 Inch Dimensions | 📐 Metric Equivalent |
|---|---|---|
| Jar Inside Diameter | 7 1/4 in. | 184 mm |
| Jar Inside Depth | 7 1/4 in. | 184 mm |
| Ring Outside Diameter | 7 1/8 in. | 181 mm |
| Ring Material Size | 3/4 in. x 1/8 in. | 19 mm x 3 mm |
| Shelf Dimensions | 6 1/2 in. x 3/4 in. x 1/8 in. | 165 mm x 19 mm x 3 mm |
| Shelf Clearance from Ring | 5/8 in. | 15.9 mm |
⚙️ Procedure and Application
The test involves placing a sample of sized coal into the tumbler, which is then rotated. The resulting impact and abrasion between coal particles and the jar walls simulate the stresses of handling. This provides a measure of the coal’s resistance to breakage, directly indicating its friability. The method is particularly useful for assessing potential size degradation in mechanical feed devices and for classifying coal based on rank and grade.
It is important to note that the test is designed for comparing coals for similarity rather than for precise tolerances. Safety precautions as per the standard should be followed during testing, and the apparatus must be maintained according to specifications to ensure consistent results.
Note: The standard underwent editorial changes in December 2019, but these do not affect the technical requirements or test outcomes.
Important: The frame must be constructed with rivets, not bolts, as specified to maintain structural integrity and test consistency.
❓ Frequently Asked Questions
🔍 What does the tumbler test for coal measure?
It measures the relative friability of sized coal, indicating its tendency to break into smaller pieces upon impact and abrasion during handling.
💡 How are the apparatus dimensions standardized?
The jar has specific dimensions of 7 1/4 inches in diameter and depth, with shelves having a clearance of 5/8 inch from the rings, all in inch-pound units.
⚡ Can this test method classify different coal types?
Yes, it is useful for differentiating between certain ranks and grades of coal, aiding in classification purposes.
📌 What units are used in this standard?
Values are stated in inch-pound units as the standard, with mass optionally expressed in metric values.