EN 1446 large profiled wall pipe ring stiffness test to determine the ring stiffness of circular cross-section thermoplastic pipes, the pipe range can be from 200mm to 4000mm or more. The nominal ring stiffness describes the resistance of a pipe to deformation by means of a vertically acting force. 

Conform with Standard ISO 9969, ISO 9967. ASTM D2412, EN1446, AS 1462.22

Feature of RST-3 series:
Suitable for large size pipe test (over 1000mm dia.);  computer control, three or more load cells.
 
Principle of ring stiffness: 
The ring stiffness is determined by measuring the force and the deflection while deflecting the pipe at a constant deflection speed.
A cut length of pipe supported horizontally is compressed vertically between two parallel flat platens moved at a constant speed that is dependent upon the diameter of the pipe.
A plot of force versus deflection is generated. The ring stiffness is calculated as a function of the force necessary to produce a 3% diametric deflection of pipe.

Principle of creep ratio: 
A cut length of pipe is placed between two parallel flat horizontal plates and a constant compressive force is applied for 1008 h (42 days). The deflection of the pipe is recorded at specified intervals so as to prepare a plot of pipe deflection against time. The linearity of the data is analysed and the creep ratio is calculated as the ratio between the two years’ extrapolated deflection value and the measured 6 min (0.1 h) deflection.

Other name:
Pipe ring stiffness tester, PVC pipe ring stiffness test, HDPE pipe ring stiffness testing equipment, PE pipe creep rate test, thermoplastic pipe creep ratio test.

The main frame feature: 

1. High precision American force sensors: interval selectable. Force accuracy within ±0.5%.

2. Power system: American force sensors, imported AC servo motor, imported AC driver + Shanghai reduction gear + Taiwan rolling ball screw + synchronous belt drive.

3. Control system: Uses Pulse Command control method for more precise control. The central adjustment plate allows for quick coarse adjustment and slow fine adjustment. Automatically returns to the origin and saves automatically after testing.

4. Display method: Fasttest Professional version WIN11 testing software displays on computer screen.

5. Simplified full-range single gear and precise full-range four gears force linear double calibration system.

6. Luxurious testing interface software supports control modes such as constant speed, positional displacement, constant load (with adjustable hold time), constant load increment rate, constant stress increment rate, and constant strain increment rate, along with multi-stage control mode to meet various testing requirements.

7. Full range displacement: Encoder 2500 P/R, increases precision by 4 times, uses LINE DRIVE encoder for anti-interference capability*, displacement resolution 0.001mm. Small deformation: Metal extensometer, resolution 0.001mm (optional).

8. Safety device: Overload emergency shutdown device, upper and lower stroke limit device, automatic power-off system for leakage, automatic disconnection stop function.

Why do plastic pipes need to execute the ring stiffness testing？ 

The main purpose of conducting ring stiffness tests on plastic pipes is to evaluate their resistance to deformation under external pressure, ensure that they can withstand external loads such as soil and pressure in practical applications, and avoid rupture or failure due to excessive deformation.  ‌

The role of ring stiffness test

The ring stiffness reflects the ability of the pipe to resist deformation when subjected to vertical compression, directly affecting its stability and durability. The experiment simulates the external pressure environment to test the load bearing capacity of the pipe under specific deformation (such as 3% deformation in the diameter direction), in order to determine its ring stiffness index.  ‌
Importance in practical applications

Ensure bearing capacity: Pipes with high ring stiffness deform less under soil pressure, which can reduce problems such as pipe misalignment and leakage caused by external pressure.  ‌
Extended service life: Unqualified ring stiffness may cause the pipeline to rupture due to excessive external pressure during use, shortening its service life.  ‌
Compliant with engineering standards: like China's "Test Method for Ring Stiffness of Plastic Pipes" (GB/T 9647) explicitly requires all types of pipes to undergo ring stiffness testing to ensure their mechanical properties meet national standards.

^{ISO 9969  "Thermoplastics pipes -- Determination of ring stiffness”
ISO9967  "Thermoplastics pipes -- Determination of creep ratio“}