Gas cylinders. Refillable seamless steel tubes of water capacity between 150 l and 3000 l. Design, construction and testing|Dangerous materials, Gas cylinders, Design, Impact testing, Penetrant flaw detection, Volume, Performance testing, Mechanical testing, Control samples, Heat treatment, Re-usable, Tensile testing, Inspection, Liquefied gases, Formulae (mathematics), Mechanical properties of materials, Compressed gases, Seamless pipes, Thickness, Ultrasonic testing, Environment (working), Hardness testing, Dimensional measurement, Marking, Certificates of conformity, Pressure vessels, Calibration, Chemical composition, Assembling, Surface defects, Visual inspection (testing), Tensile strength, Compositional tolerances, Hydraulic tests, Stainless steels, Quality assurance