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D2666-96 – Standard Test Method Technical Guide
📐 Scope and Referenced Documents
ASTM D2666-96a is an American National Standard that specifies requirements for polybutylene (PB) plastic tubing. The tubing is outside diameter controlled and produced in standard thermoplastic tubing dimension ratios. It is pressure rated for water service. The specification provides criteria for classifying PB tubing, a system of nomenclature, and mandatory requirements for materials, workmanship, dimensions, sustained pressure resistance, and burst pressure. Additionally, methods for marking the tubing are included.
The standard references several ASTM standards for testing and terminology, as well as federal and military standards for marking. Key referenced standards include:
| 🟦 Standard | 📏 Title |
|---|---|
| D 618 | Practice for Conditioning Plastics for Testing |
| D 1598 | Test Method for Time-to-Failure of Plastic Pipe Under Constant Internal Pressure |
| D 1599 | Test Method for Short-Time Hydraulic Failure Pressure of Plastic Pipe, Tubing, and Fittings |
| D 1600 | Terminology for Abbreviated Terms Relating to Plastics |
| D 1708 | Test Method for Tensile Properties of Plastics by Use of Microtensile Specimens |
| D 2122 | Test Method for Determining Dimensions of Thermoplastic Pipe and Fittings |
| D 2581 | Specification for Polybutylene (PB) Plastics Molding and Extrusion Materials |
| D 2837 | Test Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials |
| F 412 | Terminology Relating to Plastic Piping Systems |
| F 699 | Practice for Accelerated Conditioning of Polybutylene Pipe and Tubing for Subsequent Quality Control Testing |
In addition, Federal Standard No. 123 and Military Standard MIL-STD-129 are referenced for marking for shipment, and NSF Standards No. 14 and No. 61 address plastic piping components and drinking water system health effects.
⚙️ Terminology and Test Methods
Section 3 of the standard provides definitions for terms specific to polybutylene tubing. Hydrostatic design stress is defined as the estimated maximum tensile stress the material is capable of withstanding continuously with a high degree of certainty that failure will not occur. This stress is circumferential when internal hydrostatic water pressure is applied. The relationship between dimensions, hydrostatic design stress, and pressure rating is given by the ISO equation: 2S/P = (D0/t) – 1, where:
S = hydrostatic design stress (psi)
P = pressure rating (psi)
D0 = outside diameter (inches)
t = wall thickness (inches)
The following table summarizes key definitions:
| 🟦 Term | 📐 Definition |
|---|---|
| Hydrostatic Design Stress | The estimated maximum tensile stress the material can withstand continuously without failure, applied circumferentially. |
| ISO Equation | 2S/P = (D0/t) – 1; used to relate dimensions, design stress, and pressure rating. |
⚠️ Safety Hazard Caveat: As per Section 1.4, the test methods portion (Section 7) of this specification does not address all safety concerns. It is the responsibility of the user to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
💡 Application Note: The ISO equation is critical for design calculations. For accurate pressure rating determination, ensure that the hydrostatic design stress value is obtained from test method D2837 and that dimensions are per D2122.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D2666-96a?
The specification covers polybutylene (PB) tubing that is outside diameter controlled, made in standard thermoplastic tubing dimension ratios, and pressure rated for water. It includes criteria for classifying tubing, a nomenclature system, and requirements for materials, workmanship, dimensions, sustained pressure, burst pressure, and marking.
💡 What are the key test methods for pressure performance?
Test Method D1598 (Time-to-Failure Under Constant Internal Pressure) evaluates sustained pressure capability, while D1599 (Short-Time Hydraulic Failure Pressure) measures burst pressure. These are referenced in the standard for quality control.
⚡ How does the ISO equation relate dimensions and pressure rating?
The ISO equation (2S/P = (D0/t) – 1) links hydrostatic design stress (S), pressure rating (P), outside diameter (D0), and wall thickness (t). It is fundamental for determining the required wall thickness for a given pressure rating.
📌 What safety precautions are mentioned in the standard?
Section 1.4 provides a safety hazards caveat for the test methods portion, emphasizing that users should establish appropriate safety and health practices and comply with regulatory limitations before conducting tests.