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D3393-91 – Standard Test Method Technical Guide
📜 Scope and Definitions
This specification, D3393‑91 (Reapproved 2022), sets minimum hydrostatic resistance requirements for fabrics coated with rubber or plastics. Coated fabrics meeting these requirements are considered waterproof. SI units are the standard; inch‑pound units are for information only. The standard also delivers essential definitions to promote common understanding:
Waterproofness: The property of impenetrability by liquid water.
Water Repellency: The property of being resistant to wetting by liquid water.
Water Resistance: The property of retarding both penetration and wetting by liquid water.
The standard includes a precautionary caveat noting that it does not address all safety concerns; users must establish appropriate safety, health, and environmental practices before use.
⚙️ Test Apparatus and Procedure
The test method employs a hydrostatic tester capable of applying a pressure of 207 kPa (30 psi) within 6 s with an accuracy of ±7.0 kPa (±1.0 psi). The apparatus has two concentric ring clamps (inner diameter 31.5 ± 0.5 mm; 1.24 ± 0.02 in.). The inside edges of the clamps must be rounded to 0.3 – 0.5 mm (0.01 – 0.02 in.) to prevent cutting the specimen. A seal on the lower clamp avoids leakage during the test. Circular specimens are exposed to the specified pressure, and the upper surface is visually examined for water penetration. Records of compliance must be maintained; statistically based sampling plans may be used.
| 📏 Parameter | 📐 Specification |
|---|---|
| Hydrostatic Pressure | 207 kPa (30 psi) |
| Pressure Accuracy | ±7.0 kPa (1.0 psi) |
| Ring Clamp Inner Diameter | 31.5 ± 0.5 mm (1.24 ± 0.02 in.) |
| Edge Radius | 0.3 – 0.5 mm (0.01 – 0.02 in.) |
| Pressure Application Time | Within 6 s |
📊 Key Measured Properties and Compliance
The primary measured property is hydrostatic resistance. Compliance requires no water penetration at the minimum pressure. The specification does not cover water repellency or water resistance. Producers and fabricators must retain compliance records; additional sampling and testing may be agreed upon between purchaser and seller in case of disputes. The standard was developed in accordance with internationally recognized principles on standardization.
| 🟦 Property | ⚡ Requirement |
|---|---|
| Minimum Hydrostatic Resistance | 207 kPa (30 psi) |
| Test Duration for Pressure Application | ≤ 6 s |
💡 Tip: Ensure the ring clamps have properly rounded edges (0.3 – 0.5 mm) to avoid cutting the test specimen. The seal on the lower clamp must be intact to prevent leakage during the test.
⚠️ Note: This specification addresses waterproofness only. Do not use it to evaluate water repellency or water resistance of coated fabrics. For those properties, refer to other appropriate standards.
❓ Frequently Asked Questions
🔍 What is the definition of waterproofness according to D3393‑91? Waterproofness is defined as the property of impenetrability by liquid water, as given in Terminology D1566.
💡 What is the minimum hydrostatic pressure required for compliance? The minimum requirement is a hydrostatic resistance of 207 kPa (30 psi), applied within 6 seconds.
⚡ How is the test performed on coated fabrics? Circular specimens are clamped between ring clamps and subjected to the specified hydrostatic pressure. The upper exposed surface is examined visually for any sign of water penetration.
📌 What safety concerns are mentioned in the standard? The standard includes a precautionary caveat stating that it does not address all safety concerns. Users are responsible for establishing appropriate safety, health, and environmental practices before use.