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D4915-96 – Standard Test Method Technical Guide
📐 Scope and Sampling Limitations
This guide describes manual sampling procedures for coal contained in railroad cars, intended for general analysis and total moisture determination. The gross sample must be crushed and prepared in accordance with Method D 2013 and Test Methods D 2234. Sampling is limited to the top 18 to 24 inches of a railcar; samples from this layer do not represent material below the point of penetration. Samples collected under Condition D (from stationary sources) are considered less representative than those taken under Conditions A, B, or C as defined in Test Methods D 2234.
Referenced standards for this guide include:
| 🟦 Standard Designation | 📏 Title |
|---|---|
| D 431 | Test Method for Designating the Size of Coal from its Sieve Analysis |
| D 2013 | Method of Preparing Coal Samples for Analysis |
| D 2234 | Test Methods for Collection of a Gross Sample of Coal |
| E 105 | Practice for Probability Sampling of Materials |
| E 177 | Practice for Use of the Terms Precision and Bias in ASTM Test Methods |
Terminology defines accuracy as a measure of the reliability of a sample or observation, specifically the closeness of agreement.
⚙️ Sampling Procedure and Precautions
During increment removal, avoid spillage of coal from the sampling device, as spillage can lead to size biasing across different coal sizes. The procedures are designed to reduce variance to an acceptable level while remaining physically and economically feasible. Factors such as variations in railcar loading equipment, lack of access to predictable coal portions, time, weather, and the heterogeneous nature of coal can interact, inducing unacceptable bias and variance.
This guide should not be considered a substitute for more reliable methods like full-stream mechanical sampling. Any modifications to the sampling procedure should be accompanied by an understanding of both the product and the potential effects on sample integrity.
💡 Tip: Ensure no spillage occurs during increment removal to prevent size biasing. Use proper sampling tools and techniques.
⚡ Caution: Samples obtained under Condition D are less representative than those from Conditions A, B, or C. Consider using mechanical sampling for more reliable results.
❓ Frequently Asked Questions
🔍 What is the primary purpose of this guide?
This guide provides manual sampling procedures for coal in railroad cars for general analysis and total moisture determination.
💡 Why is sampling restricted to the top 18-24 inches?
Due to limitations in access and practical constraints, this guide only covers sampling from the top layer, and it does not represent coal below that depth.
⚡ How does spillage affect sample quality?
Spillage can cause size biasing, where certain coal sizes are over- or under-represented, affecting the sample’s accuracy.
📌 Which standards are referenced for sample preparation?
The gross sample is to be crushed and prepared in accordance with Method D 2013 and Test Methods D 2234.