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D3374 – Standard Test Method Technical Guide
🧵 Scope and Classification
This specification, designated D3374/D3374M-14, covers vinyl-coated glass yarns intended for weaving into insect screening. These yarns are manufactured in two basic classes to provide satisfactory strength, durability, and insect protection. The specification requires that the values for either SI or inch-pound units be regarded separately as standard.
| 🟦 Class | 📏 Nominal Thickness (mm) | 📐 Nominal Thickness (in.) |
|---|---|---|
| Class 1 | 0.292 | 0.0115 |
| Class 2 | 0.330 | 0.0130 |
⚠️ Units Warning: While nominal thicknesses are provided in both SI and inch-pound units, they are not exact equivalents. To ensure conformance with the specification, each system must be used independently of the other. Combining values may result in non-conformance.
🧪 Test Methods and Material Verification
Compliance with D3374 requires verifying critical properties through standardized ASTM test methods. The linear density (yarn number) is determined according to Test Method D1907. Tensile properties are evaluated using the single-strand method in D2256. To measure the vinyl coating content, the ignition loss test per D4963 is employed. For assessing durability against environmental exposure, particularly UV radiation, Practice D4329 is referenced. Terminology related to glass fiber products is governed by D7018, while general textile terms fall under D123.
| ⚡ Property Evaluated | 📏 Referenced Standard | 🎯 Method Overview |
|---|---|---|
| Linear Density | D1907 | Yarn Number by Skein Method |
| Breaking Force | D2256 | Tensile Properties by Single Strand |
| Coating Content | D4963 | Ignition Loss of Glass Strands |
| UV Resistance | D4329 | Fluorescent UV Lamp Exposure |
💡 Testing Tip: The standard also references AATCC Evaluation Procedure 1 (Gray Scale for Color Change) and ANSI/ASQC Z1.4 and Z1.9 for statistical sampling. Always verify the latest edition of these documents for complete testing guidance.
📦 Sampling and Lot Inspection
Acceptance testing requires a randomized lot sample where yarn packages serve as the primary sampling unit. For the critical properties of Yarn Number, Ignition Loss, and Breaking Force, the sampling procedures and the number of specimens must conform to the ANSI/ASQ Z1.9 standard. This standard provides tables for inspection by variables for percent nonconforming, where the lot size dictates the required sample size. In the absence of a specific agreement between the purchaser and supplier, this statistical approach is the mandatory method for acceptance testing.
❓ Frequently Asked Questions
🔍 What are the principal classifications of vinyl-coated glass yarns?
The standard defines two classes based on nominal thickness: Class 1 at 0.292 mm (0.0115 in.) and Class 2 at 0.330 mm (0.0130 in.).
💡 Which standard governs the sampling procedure for acceptance testing?
For properties such as Yarn Number, Ignition Loss, and Breaking Force, the sampling plan must adhere to ANSI/ASQ Z1.9 (Sampling Procedures for Inspection by Variables for Percent Nonconforming).
⚡ Why is the ignition loss test (D4963) critical for this standard?
This test measures the amount of vinyl coating on the glass yarn. The coating level is fundamental to ensuring the final insect screening achieves the required weather resistance and structural integrity.
📌 Is it permissible to mix SI and inch-pound units during evaluation?
No. The specification explicitly states in Section 1.2 that the values in each system must be regarded separately. Combining values from the two systems may directly result in non-conformance with the standard.