Seamless gas cylinders, as crucial storage and transportation containers for high-pressure gases, rely on a scientific and rigorous inspection process for safety. Inspection is conducted throughout the entire process of cylinder manufacturing, use, and periodic re-inspection, aiming to identify and eliminate structural defects and performance degradation, ensuring reliable resistance to design pressure and changes in operating conditions during service.
The inspection process begins at the raw material and manufacturing stages. Alloy steel or aluminum alloy billets used for seamless gas cylinders must undergo chemical composition analysis and mechanical property testing to confirm that their strength, toughness, and corrosion resistance meet standards, preventing internal inclusions and delamination defects from entering the forming process. During forming, the tube blank is hot-spinned or cold-drawn to form the cylinder blank, which is then stretched and narrowed. At this stage, a preliminary inspection of geometric dimensions and wall thickness uniformity is required to ensure there are no potential risks of localized thinning or stress concentration.
Subsequent heat treatment and machining stages are also accompanied by quality inspection. Heat treatment must be performed according to the process curve. After completion, samples are taken for metallographic examination and hardness testing to verify whether the material properties meet the strengthening requirements. During the machining stage, the focus is on inspecting the cylinder neck threads, sealing surface dimensions, and surface roughness to ensure reliable fit with the valve and prevent leaks caused by machining errors.
Non-destructive testing and pressure testing are core inspection items in the manufacturing stage. The cylinder body must undergo ultrasonic testing and magnetic particle testing sequentially. The former detects internal cracks, pores, and inclusions, while the latter identifies surface folds, cracks, and grinding burns. After passing the tests, a hydrostatic test is conducted at a pressure at least 1.5 times the nominal working pressure. The pressure holding time depends on the volume and standard. The system observes for leaks, permanent deformation, or abnormal sounds to verify the cylinder's strength and sealing integrity. All test data must be recorded and archived to ensure traceability of the manufacturing process.
Before leaving the factory, the cylinders undergo a final inspection, including verification of appearance quality, marking clarity, valve assembly tightness, and accessory integrity. Cylinders that pass inspection are affixed with an inspection mark indicating the manufacturing date, nominal pressure, next inspection date, and manufacturer information before being put into use.
Periodic inspections during use typically occur every three years. The inspection includes visual inspection, wall thickness measurement, valve function testing, and a second hydrostatic test. If necessary, a pneumatic burst test will be conducted to assess the ultimate load-bearing capacity. Cylinders found to have dents, excessive corrosion, cracks, or valve damage should be immediately scrapped or downgraded; repair and refilling are strictly prohibited.
The entire inspection process is performed by qualified institutions and personnel. Testing equipment must be calibrated regularly, and testing methods must comply with current national or international standards. Through a combination of rigorous manufacturing inspection, periodic re-inspection, and usage supervision, the seamless gas cylinder inspection process constructs a safety barrier covering the entire life cycle, providing a solid guarantee for the safe storage and transportation of high-pressure gases.
