Scaffold Steel Pipe Testing

Scaffolding steel pipe inspection mainly conducts scientific testing and analysis on the appearance quality and dimension deviation testing, tensile property testing, bending property testing, flattening property testing, galvanized layer quality testing and chemical composition analysis, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Appearance quality and dimension deviation testing: This item mainly checks whether there are the defects such as the cracks, scars, delaminations, hard bends, burrs, press marks and scratches on the scaffolding steel pipe surfaces. At the same time, the dimensions such as the outer diameters, wall thicknesses, lengths and end face bevel cutting deviations are precisely measured, ensuring that they meet the tolerance ranges allowed by the standards. This is the basis for ensuring that the steel pipes can be smoothly assembled and safely loaded.

Tensile property testing: This is the core item of evaluating the mechanical properties of the steel pipe material. Through the tensile testing, the yield strength, tensile strength and elongation after fracture of the steel pipe are determined. These indicators are directly related to the load-bearing capacity and deformation ability of the steel pipe in the scaffolding systems, and are the key to preventing the plastic deformation or fracture of the structures.

Bending property testing: The scaffolding steel pipes may bear certain bending stresses during the installation and use. The bending testing simulates this working condition. The specimen is bent around the bending mandrel of the specified diameter to the specified angle, and whether there are the cracks or delaminations on the outer side of the specimen bending area is checked, to evaluate the plastic deformation ability and processing performance of the steel pipe.

Flattening property testing: This test is used to evaluate the ductility and welding quality of the steel pipe. A section of the steel pipe specimen is placed between two parallel compression plates and uniformly flattened to the specified height, checking whether there are the cracks or welding defects on the specimen, especially suitable for evaluating the weld quality of the welded steel pipes and the overall plasticity of the pipe body.

Galvanized layer quality testing: For the galvanized scaffolding steel pipes, the quality of the galvanized layers needs to be tested to evaluate the anti-corrosion ability. The main testing items include the galvanized layer thicknesses (adopting the magnetic thickness measurement method), adhesion (such as the hammer testing) and uniformity (copper sulfate immersion testing), ensuring that the galvanized layers can effectively isolate the corrosive media and extend the service lives of the steel pipes.

Chemical composition analysis: Through the methods such as the spectrometry analysis or chemical titration of the steel pipe material, the contents of the elements such as the carbon (C), silicon (Si), manganese (Mn), phosphorus (P) and sulphur (S) are determined. The chemical composition directly affects the weldability, cold working performance and final mechanical properties of the steel pipe, and is the important basis for judging whether the material designation is qualified.

Testing Scope

Classification by material: Mainly covering the welded steel pipes or seamless steel pipes made of the carbon structural steels and low-alloy high-strength structural steels such as the Q235 and Q345 designations. The mechanical property indicator requirements of the steel pipes of the different materials are different. During the testing, the material must be clearly identified and judged according to the corresponding standards.

Classification by process: Including the welded steel pipes such as the longitudinally welded steel pipes and high-frequency welded pipes, as well as the hot-rolled seamless steel pipes. For the welded steel pipes, the testing of the weld areas needs to be emphatically focused on; for the seamless steel pipes, the overall uniformity of the pipe body needs to be focused on.

Classification by surface treatment: Including the non-galvanized black steel pipes and hot-dip galvanized steel pipes. The black steel pipes mainly test their basic mechanical and dimension properties; in addition to the above items, the galvanized layer related items must be added for the galvanized steel pipes.

Classification by specification: The testing scope covers the steel pipe specifications commonly used in the scaffolding projects. For example, the steel pipes with the outer diameter of 48.3 mm and wall thicknesses of 3.5 mm or 3.6 mm are the most common specifications at home and abroad. For the steel pipes of the different outer diameters and wall thicknesses, the testing items such as the dimension tolerances and theoretical weights need to be adjusted accordingly.

Classification by use state: Including both the newly ex-factory steel pipes and the old steel pipes in service or intended to be re-put into use. For the old steel pipes, in addition to the routine items, the rust depths, wall thickness reductions and possible damage conditions need to be additionally tested, evaluating their remaining load-bearing capacities.

Classification by standard system: The testing needs to be carried out according to the standards of the different countries or regions, such as the Chinese GB/T 3091 and GB/T 13793, British BS 1139 and American ASTM A53. The testing scope needs to clearly specify the corresponding product standards and testing method standards.

Testing Methods

Dimension measurement method: The measuring tools such as the outer diameter micrometers, wall thickness gauges (such as the ultrasonic thickness gauges), steel tape measures and right-angle rulers are used for the direct measurement. The outer diameters and wall thicknesses should be measured in the multiple directions at both ends and middle cross-sections of the steel pipe, and the average values and minimum values are compared with the standards. The end face bevel cutting degrees are measured with the right-angle rulers and feeler gauges.

Tensile testing method: In accordance with the standards such as GB/T 228.1, the standard tensile specimens are cut or machined from the steel pipe and tested on a universal material testing machine. By recording the load-displacement curves, the yield strength, tensile strength and elongation after fracture are accurately calculated, and the test rates need to be strictly controlled according to the standard provisions.

Bending testing method: In accordance with the standards such as GB/T 244, the support roller type or V-shaped die type bending devices are adopted. The specimen of the specified length is placed on two support rollers, and the pressure is applied to the specimen through the bending mandrel, making it bend to the angle specified by the standard (such as 180°), and then whether there are the cracks on the outer side of the bending area is visually checked.

Flattening testing method: According to the GB/T 246 standard, a section of the steel pipe specimen of a certain length is cut and placed between the two parallel compression plates of the testing machine. The pressure is applied continuously or in stages, flattening the specimen until the distance between the two plates reaches the specified value (usually related to the outer diameter of the steel pipe), and after maintaining for a certain time, the pressure is released and whether there are the cracks or weld cracking on the specimen is checked.

Galvanized layer testing method: The galvanized layer thicknesses are measured with the magnetic thickness gauges at the multiple points uniformly distributed on the steel pipe surfaces; the adhesion can be tested with the hammer testing, using a hammer to strike the raised parts with the specific forces and checking whether the coating is peeled off; the uniformity commonly uses the copper sulfate solution immersion method, observing whether the substrate metal is exposed on the surfaces after the specified times of immersions.

Chemical composition analysis method: The spark direct-reading spectrometry is mainly adopted for the fast and multi-element simultaneous analysis. The traditional chemical analysis methods can also be adopted, such as using the carbon-sulphur analysers to determine the carbon and sulphur contents, and using the spectrophotometry to determine the contents of the phosphorus, silicon, manganese and other elements, ensuring the accurate and reliable analysis results.

Testing Standards

Domestic Standards:

1. GB/T 3091, Welded steel pipe for low pressure liquid delivery

2. GB/T 13793, Longitudinal welded steel pipes

3. GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

4. GB/T 244, Metallic materials — Tube — Bend test

5. GB/T 246, Metallic materials — Tube — Flattening test

6. GB/T 229-2020, Metallic materials — Charpy pendulum impact test method

7. GB/T 232-2010, Metallic materials — Bend test method

8. GB/T 230.1-2018, Metallic materials — Rockwell hardness test — Part 1: Test method

9. GB/T 4340.1-2009, Metallic materials — Vickers hardness test — Part 1: Test method

International Standards:

1. ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature

2. ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

3. ASTM A53, Standard specification for pipe, steel, black and hot-dipped, zinc-coated, welded and seamless

4. BS 1139, Metal scaffolding — Part 2: Couplers and fittings for scaffolding

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Universal material testing machine: This is the core equipment for the mechanical property tests such as the tensile, compression and bending. It needs to have the sufficient load capacity (usually above 300 kN) and precise load and displacement measurement and control systems, and can automatically draw the stress-strain curves and calculate the various mechanical property parameters.

Dimension measuring tools: Including the outer diameter micrometers with the 0.01 mm precision, ultrasonic thickness gauges for measuring the wall thicknesses, steel tape measures, vernier callipers, right-angle rulers and feeler gauges. These tools need to be regularly sent to the metrology departments for verification and calibration, ensuring the accuracy and traceability of the measurement data.

Bending testing machine and flattening testing machine: The bending testing machine is equipped with the bending mandrels and support rollers of the different diameters. The flattening testing machine usually has two large-area parallel compression plates, which can apply the pressure to the steel pipe specimens smoothly and uniformly. Some universal testing machines can also complete these two tests by replacing the fixtures.

Galvanized layer testing instruments: The magnetic thickness gauges are used for the non-destructive measurement of the non-magnetic coating thicknesses on the magnetic substrates. In addition, the laboratory needs to be equipped with the hammer testing devices, and the containers and chemical reagents required for the copper sulfate solution immersion testing, to complete the qualitative or quantitative testing of the adhesion and uniformity of the galvanized layers.

Chemical composition analyser: The spark direct-reading spectrometer is the mainstream equipment, which can quickly excite the steel pipe samples and determine the contents of the various elements by analysing the intensities of the characteristic spectral lines. The auxiliary equipment may include the carbon-sulphur analysers, spectrophotometers, as well as the cutting machines and sample grinding machines for the sample preparation.

Macro inspection and non-destructive flaw detection equipment: Including the tools such as the magnifying glasses and endoscopes for checking the surface and internal macro defects. For the higher requirements or old pipe evaluations, the ultrasonic flaw detectors may be used to detect the internal defects, or the magnetic particle flaw detectors may be used to detect the surface and near-surface micro cracks.