Overview
ISO 11173:1994 specifies a standardized testing method known as the staircase method for evaluating the resistance of thermoplastic pipes to external blows. This international standard applies specifically to thermoplastic pipes with circular cross-sections and is intended for isolated production batches tested at 0 °C. It provides a reliable, repeatable procedure to determine the impact resistance, essential for assuring the durability and safety of plastic piping systems used in various industries.
Key Topics
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Scope and Application
The standard is designed for thermoplastic pipes of circular cross-section and focuses on their capacity to withstand external impact forces. Testing is conducted at a controlled temperature of 0 °C, with recommendations for lower-temperature testing (e.g., -20 °C) if required.
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Test Principle
The staircase method involves subjecting pipe specimens-cut to length and randomly selected-to single, controlled impacts by a free-falling weighted striker (percuteur). The drop height is adjusted incrementally based on whether the specimen fails or passes, providing a clear quantitative measure of impact resistance.
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Equipment and Specimen Preparation
- A vertical drop test machine with a guided weighted striker having specific hemispherical or segmental ends, depending on mass.
- Specimens are sections of pipe approximately 200 mm long, with ends cut perpendicularly and free of defects.
- Support fixtures include rigid V-blocks positioned to simulate realistic impact conditions.
- Conditioning of specimens at 0 °C or specified temperatures for reproducibility.
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Testing Procedure
- Starting with a preliminary test to estimate failure height (Hs0), the main test involves increasing or decreasing drop heights by fixed increments based on specimen failure results.
- The test continues until enough data points are collected to statistically determine the height at which 50% of specimens fail under impact.
- Detailed criteria for defining failure include visible cracks, breaks or fissures on the inner face of the pipe.
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Results and Reporting
The output is the height at 50% failure probability (Hs0), representing the pipe’s resistance to external impact at 0 °C. The report must include pipe identification, test conditions, specimen count, failure criteria, equipment details, and environmental factors affecting results.
Applications
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Quality Control
Manufacturers of thermoplastic pipes use ISO 11173 to verify product consistency and robustness for batch acceptance before release to market.
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Product Development
R&D teams utilize this method during material selection and pipe design to improve impact resistance based on quantitative testing.
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Regulatory Compliance
Ensures that thermoplastic piping systems meet specific impact resistance thresholds mandated by building codes, safety standards, or client specifications.
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Performance Verification
Helps confirm that pipes used in harsh environments-where mechanical impact risks exist-maintain integrity, reducing leaks and failures.
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Comparative Testing
Allows benchmarking of different thermoplastic formulations, wall thicknesses, or pipe designs under uniform testing conditions.
Related Standards
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ISO 6603-1:1985 – Plastics - Determination of multiaxial impact behavior of rigid plastics - Part 1: Falling dart impact test, which complements ISO 11173 by describing test techniques for plastics under impact.
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ISO/TC 138 series – Covers broader terminology, testing, and specifications related to plastic tubes, fittings, and valves used for fluid transport.
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Product-specific ISO standards often reference ISO 11173 for external impact resistance requirements.
Keywords: ISO 11173, thermoplastic pipes, impact resistance test, staircase method, external blow resistance, pipe testing at 0°C, plastic pipe standards, thermoplastic pipe durability, standardized pipe testing, ISO standards for pipes, plastic impact testing.