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D293 – Standard Test Method Technical Guide
🎯 Scope and Significance of the Coke Sieve Analysis
The ASTM D293/D293M −18 standard provides the definitive test method for determining the particle size distribution of coke. This method is essential for verifying that a coke product meets specific size specifications. It details the process of separating a representative gross sample into defined size fractions, which are then reported as a mass (weight) percent of the original sample (Section 1.1, Section 3.1). The standard is intended to be used independently with either SI or inch-pound units, and values from the two systems must not be combined (Section 1.2).
⚠️ Critical Performance Criterion: When selecting a nest of sieves for complete characterization, it is mandatory that no single sieve retains more than 25 % of the gross sample mass. This prevents sieve overloading and ensures accurate particle separation (Section 4.1.1).
⚙️ Apparatus Specifications and Test Sample Requirements
The reliability of a sieve analysis is directly tied to the quality of the apparatus and sampling methods. The standard defines rigorous specifications for all equipment, which must be adhered to strictly (Section 4).
| 🟦 Apparatus Component | 📏 Key Specification | 🎯 Applicable Conditions |
|---|---|---|
| Sieve Cloth & Type | Square-hole sieves conforming to Specification E11. | Large sieves (>100 mm [4 in.]) require mutual agreement on specs. |
| Sieve Frame & Area (Coke ≥ 38.1 mm) | 0.56 to 0.84 m² (6 to 9 ft²). Heavy double-crimped wire. | Square or rectangular frames. |
| Sieve Frame & Area (Coke < 38.1 mm) | 0.19 to 0.37 m² (2 to 4 ft²). Double-crimped wire. | Square or circular frames. |
| Weighing Balance | Platform type preferred; sensitivity of 0.025 kg (0.05 lb). | Graduations must allow reading 0.05 kg (0.1 lb) without interpolation. |
The test sample itself must be collected and prepared in strict compliance with Practice D346/D346M to ensure the sample accurately represents the bulk material (Section 5.1).
📏 Detailed Testing Procedure and Material Handling
The sieving procedure is methodical. The process begins with the sieve having the largest opening. The sample must be introduced in quantities small enough to prevent plugging or blinding the sieve cloth. A critical manual assessment is required for large pieces: every piece of coke retained on a 38.1 mm [1½ in.] or larger sieve must be “hand-fitted.” A piece is classified as undersize if it can pass through the sieve opening in any possible orientation without the use of force (Section 6.1.1).
💡 Best Practice for Smaller Fractions: For coke passing the 38.1 mm [1½ in.] sieve, vigorous shaking is required on the subsequent sieves. While manual shaking is the standard reference, mechanical shaking is permissible provided it yields results demonstrably equivalent to the manual method (Section 6.1.2).
| ⚡ Procedure Step | 📐 Action Required | 🎯 Key Criteria |
|---|---|---|
| 1. Sieve Selection | Sequence sieves from largest to smallest opening. | No single sieve retains > 25 % of the gross sample mass. |
| 2. Oversize Handling | Hand-fit each piece on sieves ≥ 38.1 mm. | Piece is undersize if it passes without forcing in any position. |
| 3. Undersize Sieving | Shake vigorously on each succeeding sieve. | Mechanical shaking must be validated against manual shaking. |
| 4. Process Control | Limit the sample quantity on the sieve surface. | Prevent plugging and clogging of the mesh apertures. |
Following this standardized procedure ensures a repeatable and auditable size distribution profile, which is critical for quality control and process optimization in coke production and utilization.
❓ Frequently Asked Questions
🔍 What is the primary purpose of conducting a sieve analysis per ASTM D293/D293M?
The purpose is to determine the exact size distribution of a coke sample by separating it into defined fractions. These fractions are expressed as a mass percentage of the total sample, verifying conformance to size specifications (Sec. 1.1, 3.1).
💡 How should coke pieces retained on a 38.1 mm [1½ in.] sieve be treated during testing?
Each piece must be “hand-fitted” to the sieve. It is classified as undersize if it can pass through the opening in any orientation without the use of physical force (Sec. 6.1.1).
⚡ What are the exact specifications required for the weighing balance used in this method?
The standard requires a balance, preferably a platform type, with a sensitivity of at least 0.025 kg (0.05 lb) and capable of being read to 0.05 kg (0.1 lb) without interpolation (Sec. 4.2).
📌 What sieve area is required for the analysis of coke smaller than 38.1 mm [1½ in.]?
For coke smaller than 38.1 mm, sieves with a mesh area of 0.19 m² to 0.37 m² (2 to 4 ft²) are typically used, employing double-crimped wire in square or circular frames (Sec. 4.1.2).