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large pipe ring stiffness tester

large pipe ring stiffness tester

Model: RST-350/3100

Large pipe ring stiffness tester 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.



General introduction

Ring stiffness testing machine is equipment used to measure the ring stiffness of thermoplastic plastic pipes and fiberglass pipes with a circular cross-section. This equipment is widely used for testing the ring stiffness, ring flexibility, flattening, bending, and weld tensile strength of pipes such as PE double-wall corrugated pipes, spiral-wound pipes, PVC pipes, and fiberglass pipes. Its working principle is based on the double-plate vertical compression testing method, which measures the force and deformation of the pipe at a constant deformation rate to determine the ring stiffness.


Large pipe ring stiffness tester 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 ~ 3500mm dia.);  Robust structure frame, 4 columns+ 2 leading computer control, three or more load cells.


large pipe ring stiffness testerlarge pipe ring stiffness tester
Uniform 3 load cells for accuracy measuringGRP pipe ring stiffness test





Main Features

  • Key feature
  • Security function
  • Control system, Software
  • Standard

1, Two column design ensures high rigidity; 

2, Advanced closed loop AC servo control system increases the accuracy and control of the test sequence.  

3, For big pipe like 2m diameter, Three / Four load cells are connected in bridge, this strengthens the deflection resistance and improves the accuracy for tests on big diameter pipe. 

4, Our unique inner diameter measuring system makes mounting of even the largest pipe easy. 

5, The software is designed in-house and is very easy to use and runs on most modern computers. 

1), Sensor of position limitation switch; 

2), Emergency stop switch; 

3), Hardware driving system overload protection, over voltage, current protection;

4), Software over load protection. 

1), Based on full digital STC8800 measuring and control card; Data collection system use 4 channel of high accuracy 24 digit A/D conventer;

2), Real time load, deformation, corsshead displacement, test precess four kind close loop control;

3), Resolution can upto 1/500000, full range without step;

4), Level authorization management function: to improve sftware and data security, can set different password to realize several class authorization management. Different user with different right to operate the machine, avoiding unexpected mistake because human error.

5), PC control system, with advantage of high integration, reliable performance, easy adjusment etc. can real time collect test data, on-time display test curve,  test data file can be saved as ACCESS and SQL server, convenient for customer's data resource storage.

6), Automatically generate the testing report; the testing report can be displayed and printed, also it can be export in Excel/Access Format. Also, the user can edit the report format as requirement in report template;

7), Result recall function: after the test and saved, customer can open the test data and re-analysis at any time.

8), Results compare: observe several curve at same time, can fold curve or portion enlarge to analyze and compare sample characters.

9),Load~Time, Load~displacement, Displacement~time etc. curve smoothly switch, display test data, save, analysis and print.

ISO 9969  Thermoplastics pipes -- Determination of ring stiffness

ISO 9967  Thermoplastics pipes -- Determination of creep ratio

ASTM D2412 Standard Test Method for Determination of External Loading Characteristics of Plastic Pipe by Parallel-Plate Loading

EN 1446 Plastics piping and ducting systems - Thermoplastics pipes - Determination of ring flexibility

DIN 16961 Thermoplastics pipes and fittings with profiled wall and smooth pipe inside

AS/NZS 1462.22 Methods of test for plastics pipes and fittings Method 22: Thermoplastics pipes – Determination of ring stiffness

Main technical specification

Model: RST-3 seriesSuitable for small or middle size pipe test (1200mm ~ 3500mm dia.)
Max. load50Kn, 100Kn, 200KN
Load resolution0.01N
Load cell quantity3 pcs
Load accuracy±1% of reading value
Crosshead travel100mm-3700mm
Pipe Diameter range16mm to 3500mm
Speed range of crossbeam0.1 mm/min~500 mm/min, stepless, adjustable freely
Width of test space1150mm
Displacement accuracy0.001mm
Power220V/380V, 50Hz/60HZ
Pipe inner diameter measuring deviceYES
Creep Ratio Test(option)ISO 9967
Time range1~9999h59min59s
Timing resolution1s


Main Accessories

ItemQuantity
Frame1 set
   (include load cell, servo motor etc.,)
Compression platen (400*400mm)1 set
Pipe inner diameter measuring device1 set
Computer (English Win10)1 set
Professional ring stiffness test software (English)1 set
Documents (Manual, packing list, certificate)



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.

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Beijing United Test Co., Ltd.