Information on the most widely used ASTM standards within the materials testing industry
ASTM D2412: Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel-Plate Loading
Plastic pipe compression test, or pipe ring stiffness tseter is a testing standard used to determine the stiffness and load deflection of plastic pipe. This summary is intended to help you understand the basic procedure and equipment required to complete this test with accuracy.
ASTM D2412 test method covers the determination of load-deflection characteristics of plastic pipe under parallel-plate loading. It covers thermoplastic resin pipe, reinforced thermosetting resin pipe (RTRP), and reinforced polymer mortar pipe (RPMP). Pipes tested under ASTM D2412 must be smaller than the envelope of the two compression platens by at least a half an inch. Square or circular platens can be used, with most customers choosing a square platen. Care must be taken to account for the mid-section of the pipe which will expand slightly as the pipe is compressed.
The characteristics determined by ASTM D2412 test method are pipe stiffness, stiffness factor, and load at specific deflections. These calculations are made by taking load measurements at certain percentage deflections (5%, 10%, 20% etc.) and dividing the numbers into each other using the mathematical formulas from the official publication.

Test process if ASTM D2412 plastic pipe ring stiffness test:
1. Sample preparation:
Depending on the type of plastic pipe being tested, cut the specimen to the lengths specified. Be sure to cut the pipe cleanly. Condition the specimens to the temperature detailed in the specification. Prepare and test at least three specimens for each pipe. Measure the length, average diameter, and average wall thickness of the specimen.
2, Sample installation
Place the specimen horizontally, and the contact surface of the platen at both ends should be parallel to avoid axial displacement. Load the specimen by centering it on the bottom plate and apply just enough force to keep the sample in place with the upper platen.
3, Preloading:
Begin compressing the specimen at the specified rate. Apply an initial load of 50 N to eliminate the gap.
4, Formal loading:
Compressed at a rate of (5±1) mm/min, the force value (F) when the deformation reaches 3% (ΔY=0.03D, D is the initial inner diameter) is recorded.
5. Be aware of line cracking, wall cracking, wall delamination, and break. Record the load and deflection when these events are observed.
6. Stop the test at break, when the load no longer increases with deflection or when the specimen reaches the required maximum deflection.
7, Repeatability verification:
The test was repeated after rotation of the same specimen by 90°, and the average of the results was taken twice.
Related Standard
ISO 9969 specifies a test method for determining the ring stiffness of thermoplastics pipes having a circular cross section.
ISO 9969 requires that at least three samples are taken from the same pipe and labeled A, B and C. These samples are then compressed to at least 3% of the Inner Diameter and ring stiffness calculated for each sample. The ring stiffness is calculated as an average of these calculations.
The initial ring stiffness or ring stiffness to ISO 9969 or ASTM D2412 characterizes the resistance of a pipe section to radial compressive forces. The measurement occurs at low deformations of 3%.
ISO 9967:2016 Thermoplastics pipes — Determination of creep ratio
This standard specifies a method for determining the creep ratio of thermoplastics pipes having a circular cross-section.
ISO 9967 Creep Ratio Test Machine for Thermoplastic Pipes
The ISO 9967 test procedure begins by preparing a ring-shaped specimen from a thermoplastic pipe. The ring is typically cut to a length equal to the pipe's outer diameter and must be free of visible defects. Before testing, the sample is conditioned, usually at 23°C for at least 24 hours. During the test, the specimen is placed vertically between two flat, parallel plates in a compression testing machine. A constant external force is applied to the ring to compress it until a deformation equal to 3% of its mean diameter is reached. This loading should occur gradually, typically within one minute. The test apparatus must maintain this compressive load over an extended period, most commonly 10,000 hours, under controlled environmental conditions. The deformation of the ring is measured at defined intervals during the test using a precise displacement measurement device. Initial and long-term measurements are used to calculate the creep ratio. This ratio quantifies how much the ring deforms over time under constant load, which indicates the material's long-term behavior and suitability for buried, non-pressure pipe applications. Accurate time tracking and temperature control are critical throughout the process to ensure valid results. The test concludes by comparing the deformation at 30 minutes and at the final time point to calculate the creep ratio according to the formula provided in the ISO 9967 standard.
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