How to test the quality of stainless steel metal hoses?
Jun 23,2025
The quality inspection of stainless steel metal hoses requires comprehensive verification from multiple dimensions such as materials, processes, performance and certification. The specific process is as follows:
🔬 1. Material composition and structure testing
Material analysis
Use a spectrometer to verify whether the contents of chromium (≥16%), nickel (≥8%), and molybdenum (2%-3% in 316L) comply with the 304/316L standard.
Magnet test : Austenitic stainless steel (304/316L) should be non-magnetic, strong adsorption may be mixed with cheap ferritic material.
Structural inspection
Braided layer : Visual inspection or vernier caliper measurement of wire density (≥60 mesh/inch), gap should be uniform, coverage ≥95%;
Bellows : Wall thickness uniformity deviation ≤5%, bellows spacing error within ±0.1mm, the inner wall should be smooth without burrs when touched by hand.
⚙️ 2. Critical process validation
Welding quality
The laser weld seam needs to be observed under a 10x magnifying glass, showing uniform fish-scale patterns, without pores or non-fusion defects.
The fatigue life of inferior argon arc welded joints is only one third of that of laser welded ones.
Surface and dimensions
When observing the surface under natural light, there should be no cracks, scratches, rust spots or oxide layers.
The calipers are used to measure the outer diameter, wall thickness and length. The deviations need to comply with standards such as GB/T 14525-2010.
🧪 3. Core performance test
Stress test
Burst pressure : Pressurize to 1.5 times the design pressure (e.g. 1.6MPa ≥2.4MPa);
Pulse fatigue : length change rate < 0.3% after 20,000 cycles at 0-1.6MPa.
Sealing test
According to the GB 41317-2024 standard, the leakage of the gas hose is ≤10mL/h at a gas pressure of 0.02MPa (a dedicated leak detector such as ZYY-08A is required).
Bending and toughness
The minimum bending radius is ≤1.5 times the nominal diameter (GB/T 14525);
There is no ripple distortion after bending U-shaped in a low-temperature environment (-20℃ or -196℃).
Corrosion resistance
Salt spray test or lead acetate immersion to observe whether it rusts;
For a chloride ion environment, 316L material is preferred.
📋 IV. Certification and compliance
Mandatory Certification
Gas hoses will require CCC certification starting from October 2025.
Exports to the European Union must comply with the PED directive (burst pressure ≥4 times the working pressure) and CE certification.
Test Report
The third-party report should include items such as chemical composition, mechanical properties, and non-destructive testing (ultrasonic/eddy current).
Operation prompt : Industrial hoses must be inspected for burst pressure and pulse fatigue; The sealing performance of the threaded interface and the certification mark of the gas hose need to be verified separately. If the braided layer is found to be loose, the weld seam uneven or cracked during low-temperature bending, it shall be judged as unqualified.
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