Cyclic pressure test methods in ASTMD 2992

ASTM D2992 is a standard test method for fiberglass-wound fiber-reinforced thermosetting resin pipe, primarily covering cyclic pressure testing and hydrostatic strength testing. In D2992, the cyclic pressure test method primarily refers to ProcedureA – Cyclic Pressure Test. The core content is as follows:

1. Purpose

This test is used to assess the durability and fatigue life of FRP pipes under repeated pressure.

This test simulates the cyclic stresses such as water hammer and startup/shutdown that pipes may experience during long-term use by cyclically applying and releasing pressure.

2. Sample Preparation

The sample is typically a pipe section, long enough to accommodate end fittings and avoid localized stress interference. (Our European customers selected a sample length of 1.5 meters.) Both ends are sealed with end caps or fittings to ensure no leakage during circulation.

3. Cycling Pressure Conditions Cycling Range:

Typically between a specified lower and upper pressure limit (e.g., 0 bar to the specified test pressure, or a certain ratio of the design pressure). Cycling Rate: Typically 25 cycles/minute (depending on equipment capabilities and standards). Waveform: Commonly used are sinusoidal or trapezoidal pressure-on/pressure-off waveforms.

4. Test Method

Eighteen specimens were placed in a hydraulic pressure test apparatus.

Continuous pressure application and release cycles were performed at the specified pressure amplitude and frequency.

The number of cycles required for specimen failure was recorded (failure was considered to be caused by rupture, leakage, or instability).

5. Result Processing

By statistically analyzing the number of cycles to failure for multiple groups of specimens,

regression analysis can be used to predict the 10⁶ cycle life pressure or life at a specific pressure at a certain confidence level.

The results are often used to determine the design basis strength (HDB) or fatigue life rating for pipelines.

Summary:
The cyclic pressure test (Procedure A) in ASTM D2992 repeatedly pressurizes and releases FRP pipes until they fail, and then uses statistical analysis to determine their cyclic fatigue resistance.

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