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D2992-24 – Standard Test Method Technical Guide
📐 Scope and Application
This standard practice, D2992-24, establishes two procedures—Procedure A (cyclic) and Procedure B (static)—for obtaining a hydrostatic design basis (HDB) or pressure design basis (PDB) for fiberglass piping products, including RTRP (glass-fiber-reinforced thermosetting-resin pipe) and RPMP (glass-fiber-reinforced polymer mortar pipe). The practice applies to pipes with an outside diameter to wall thickness ratio of 10:1 or greater, based on thin-wall pipe design theory.
⚙️ Test Procedures and Stress Considerations
In Procedure A (cyclic) and Procedure B (static), specimens are tested under pressure to evaluate strength-regression data. End closures may be restrained, stressing only the hoop direction, or free, where hoop stress is twice the longitudinal stress. For free-end tests, the practice is limited to conditions where the longitudinal stress does not exceed 50% of the hydrostatic design stress (HDS). All data must share the same failure mode for accurate analysis.
📊 Design Basis and Limitations
The HDB is derived from regression analysis of test data. For restrained ends, the HDB applies solely to hoop stress. For thin-wall pipe, internal pressure is limited to approximately 20% of the HDS. For example, if the HDS is 5000 psi (34,500 kPa), the maximum allowable internal pressure is 1000 psig (6900 kPa). The practice may be overly conservative for pipes with continuous glass fibers designed for specific loads.
| 🟦 End Condition | 📐 Hoop Stress | 📏 Longitudinal Stress | 🎯 Limitation |
|---|---|---|---|
| Restrained Ends | Applied | Not Applied | HDB for hoop direction only |
| Free Ends | Applied (twice longitudinal) | Applied (50% of hoop) | Not for longitudinal > 50% of HDS |
| ⚡ HDS (psi) | ⚡ HDS (kPa) | 📊 Max Pressure (psig) | 📊 Max Pressure (kPa) |
|---|---|---|---|
| 5000 | 34,500 | 1000 | 6900 |
⚠️ Note 3: For pipes with intentionally placed long glass fibers to resist planned pressure loads, this practice may yield overly conservative results when operated at lower, non-damaging stresses.
💡 Note 4: Ensure all data points in the analysis share the same failure mode to accurately represent pipe life expectancy. Unintended resin matrix cracking can affect results.
❓ Frequently Asked Questions
🔍 What is the minimum diameter-to-wall thickness ratio required for this practice?
The practice applies to fiberglass pipes where the ratio of outside diameter to wall thickness is 10:1 or more.
💡 What are the two procedures defined in this standard?
The standard defines Procedure A (cyclic) and Procedure B (static) for obtaining the hydrostatic or pressure design basis.
⚡ Can this practice be used for pipe with free ends under high longitudinal stress?
No, for free-end tests, the practice is not applicable if the longitudinal stress exceeds 50% of the HDS.
📌 How is the maximum internal pressure determined from the HDS?
From Note 2, the maximum internal pressure is approximately 20% of the derived HDS. For example, an HDS of 5000 psi (34,500 kPa) limits pressure to 1000 psig (6900 kPa).