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D440-07 – Standard Test Method Technical Guide
The ASTM D440‑07 (Reapproved 2019) standard, officially titled Standard Test Method of Drop Shatter Test for Coal, establishes the definitive procedure for evaluating the relative size stability and friability of sized coal. This test provides engineers and quality‑control professionals with a reliable indication of how coal will withstand breakage when subjected to the mechanical stresses of handling at the mine, during loading, and throughout transit to the consumer. The test method is explicitly designed to emphasize dissimilarity between coals rather than to determine values within extremely narrow limits.
🔬 Purpose and Scope
As specified in Section 1.1, this test method covers the determination of size stability and its complement—friability. It is applicable for testing a selected single size of different coals, different single sizes of the same coal, and mixed sizes of the same or different coals. Note 1 clarifies that “single sizes” refer to those with fixed upper and lower sieve opening limits (selected from those designated in Section 4.2), while “mixed sizes” refer to either “slack” or a mixture of two or more single sizes.
The standard (Section 1.2) is best suited for measuring the breakage resistance of larger coals handled in thin layers—such as from loader to mine car or from loading boom to railroad car. It is also considered useful for indicating the relative size stability of composite sizes where smaller pieces may exert a cushioning effect. The values determined, when evaluated against pertinent experience with other coals (Section 3.1), serve as practical indicators of breakage in conventional transit and handling systems beyond the point of sampling.
⚙️ Apparatus and Key Specifications
Section 4.1 mandates that the shatter test machine must be identical to the apparatus described in Test Method D3038. The core equipment consists of a precisely dimensioned metal box supported above a rigidly mounted drop plate.
| 🟦 Component | 📏 Standard Requirement (Section 4.1) |
|---|---|
| Drop box width | 18 in. (457 mm) |
| Drop box length | 28 in. (711 mm) |
| Drop box depth | Approximately 15 in. (381 mm) |
| Drop plate material & thickness | Rigidly mounted cast iron or steel plate, not less than ½ in. thick |
| Reference standards | D3038, D4749, E11, E323 |
💡 Best Practice Tip: When selecting coal for testing, ensure the sample accurately represents the population of interest. For single‑size tests, adhere strictly to the upper and lower sieve limits defined per Section 4.2. For mixed‑size tests (e.g., run‑of‑mine “slack”), the sample must be a true composite of the material stream.
📊 Key Measured Properties and Interpretation
The central metrics produced by this test are size stability (the resistance to breakage) and friability (the liability to break). These complementary values allow for accurate relative classification of coal behavior under impact.
| 🎯 Property | ⚡ Definition & Significance |
|---|---|
| Size Stability | The relative ability of sized coal to withstand breakage when subjected to the drop shatter procedure. |
| Friability | The complement of size stability; indicates the inherent tendency of the coal to fragment under impact. |
| Single‑Size Coal | Coal selected with fixed upper and lower sieve limits, as designated in Section 4.2. |
| Mixed‑Size Coal | Either “slack” or a deliberate mixture of two or more single sizes of the same or different coals. |
The standard emphasizes that the results are “serviceable for ascertaining the similarity of coals in respect to size stability and friability rather than for determining values within narrow limits.” Therefore, the data are best used comparatively to predict relative performance in real‑world handling and transit.
⚠️ Units & Safety Compliance: Per Section 1.3, values stated in inch‑pound units shall be regarded as the standard. Mass may be expressed in metric values, but all physical dimensions of the apparatus must strictly adhere to the inch‑pound system. The user is responsible for establishing appropriate safety, health, and environmental practices before performing the test (Section 1.4).
🌍 International Alignment: In accordance with Section 1.5, this standard was developed following the internationally recognized principles on standardization established by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
❓ Frequently Asked Questions
🔍 What is the main objective of the Drop Shatter Test for Coal (D440‑07)?
The test method determines the relative size stability and friability of sized coal, providing a critical indication of how the coal will withstand breakage when subjected to handling at the mine and during transit to the consumer.
💡 How does the standard define “mixed sizes” of coal?
According to Note 1 in the standard, “mixed sizes” refers to either “slack” or a mixture of two or more single sizes of the same or different coals. Single sizes, by contrast, have fixed upper and lower sieve opening limits.
⚡ What are the exact dimensional requirements for the shatter test apparatus?
Section 4.1 requires the drop box to be 18 in. (457 mm) wide, 28 in. (711 mm) long, and approximately 15 in. (381 mm) deep. The box must be supported above a rigidly mounted cast‑iron or steel plate that is not less than ½ in. thick.
📌 Which referenced ASTM standards are critical for performing this test?
Key references include D3038 (Drop Shatter Test for Coke) for the apparatus design, D4749 (Sieve Analysis of Coal and Designating Coal Size), and sieve specifications E11 (Woven Wire Test Sieve Cloth) and E323 (Perforated‑Plate Sieves).