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D3173 – Standard Test Method Technical Guide
🔬 Scope and Principles of the Test
ASTM D3173/D3173M − 17a provides a standardized procedure for determining the moisture content in the laboratory analysis sample of coal and coke. The core principle involves establishing the loss in weight of the sample under highly controlled conditions of temperature, time, and atmosphere. This moisture value is primarily used to normalize and calculate other analytical results to a common dry basis, ensuring data comparability across different samples.
⚠️ Unit Independence Requirement: Values stated in SI units or inch-pound units must be used independently. Combining values from both systems into a single calculation may result in non-conformance with the standard.
| 🟦 📏 Key Parameter | 🎯 Specification / Value |
|---|---|
| Standard Designation | D3173 / D3173M − 17a |
| Oven Temperature Regulation (Coal) | 104 °C to 110 °C |
| Preheated Air Renewal Rate (Coal Oven) | 2 to 4 times per minute |
| Door Ventilation Opening (Coal Oven) | ~3.2 mm [⅛ in.] diameter hole |
| Analysis Sample Particle Size | Pass 250-µm (No. 60) sieve |
⚙️ Apparatus and Sample Preparation
The apparatus requirements differ based on the material tested. For coal, the drying oven must have a uniform temperature in all zones and a minimum air space. It must be capable of renewing the preheated, dried air inside the chamber at a rate of two to four times per minute, with the door featuring a small hole for a free flow of air. For coke, an ordinary drying oven with adequate ventilation openings is sufficient.
The analysis sample must be pulverized to pass a 250-µm (No. 60) sieve. This fine particle size ensures the effective removal of inherent moisture during the controlled heating sequence. The sample is prepared strictly according to the procedures outlined in Practice D346 (for coke) or Method D2013 (for coal).
📊 Significance and Proximate Analysis Role
The moisture percent determined by this test method is a critical input for the proximate analysis of coal and coke, which also includes ash, volatile matter, and fixed carbon. It is the foundation for calculating other analytical results to a moisture-free basis using Practice D3180. Additionally, when this value is used in conjunction with the air-dry moisture loss from Method D2013 and the total moisture from Test Method D3302, analysts can fully characterize the moisture profile of the material for reporting on an “as received” basis.
| 🟦 📐 Application Area | ⚡ Related Standard |
|---|---|
| Dry Basis Calculation Method | Practice D3180 |
| Total Moisture Determination (Coal) | Method D2013, Test Method D3302 |
| Coal Sample Preparation Protocol | Method D2013 |
| Coke Sample Preparation Protocol | Practice D346 |
| Standard Terminology for Definitions | Terminology D121 |
💡 Technical Tip: Because this test method determines moisture in the finely pulverized analysis sample, it is strictly for normalizing laboratory analytical results. It does not directly represent the total moisture content of the bulk material, which requires separate testing procedures.
❓ Frequently Asked Questions
🔍 Why is this specific moisture test critical for coal and coke analysis?
The moisture value obtained is essential for converting other analytical results (such as ash or sulfur content) to a common dry basis. This normalization removes the variable of atmospheric moisture, allowing for precise comparison of the material’s intrinsic composition.
💡 What are the exact oven specifications for testing coal samples?
The oven must maintain a temperature strictly between 104 and 110 °C. It requires a controlled atmosphere where preheated, dried air is renewed at a rate of two to four times per minute. The door must have a ventilation hole of approximately 3.2 mm [⅛ in.] in diameter.
⚡ How does the equipment differ for testing coke samples in D3173?
While the coal oven has strict requirements for temperature uniformity and a controlled airflow, the standard specifies that an ordinary drying oven with sufficient openings for air circulation is acceptable for determining moisture in coke samples.
📌 What particle size is required for the analysis sample per this standard?
The sample must be pulverized to pass through a 250-µm (No. 60) sieve. This fine grinding is critical to ensure the complete removal of inherent moisture under the controlled heating conditions of the test method.