A very well-equipped quality control lab enables the firm to ensure the quality of its products, giving it the ability to carry out all required testing within the industrial plant, making the outsourcing of this activity unnecessary. The following controls are of particular importance in the production of tubes for natural gas pipelines. PIGMENTARY DISPERSION: Thin films on tube walls are observed under the microscope to ensure the correct dispersion of pigmented materials. TRACTION STRESS RESISTANCE: Normalized testing samples are subjected to traction stress tests, in which the material must exceed breakage stretching values of 350% and point-of-flow resistance values of over 19 MegaNewtons per square meter. RESISTANCE TO HYDROSTATIC PRESSURE: The tubes are subjected to an 80ºCelsius temporizing bath for extended periods, during which they must withstand internal pressures of over 4 MegaNewtons per square meter over a period of 170 hours. DENSITY: Small sections of tubing are placed in a thermostatic column of water mixed with isopropanol, that has been calibrated with standard tracers, enabling the calculation of the material’s density. FLUIDITY INDEX: 4 grams of tubing material are placed in a Melt-Flow apparatus, under 5 kg. pressure, to determine the values of fluidity and viscosity of the material. THERMAL STABILITY: Small samples of tubing material are placed in a differential calorimeter in an inert atmospheric environment; the sample is then subjected to an oxygen flow so as to be able to determine the oxidation isotherm through the use of adequate software. SIZE ASSAYS: Thicknesses, diameters, eccentricity and oval distortion are periodically gauged, both in the lab and on line through ultrasonic testing of the material in production. Thyssen Plastic Solutions uses hi-tech equipment during the production process, including rigorous size-testing on line to constantly check the quality of its products. Thus, THYSSEN PLASTIC SOLUTIONS tubing satisfies the most stringent requirements at international level, including the following standards: * DIN 8074 * ISO 4427 * ISO 4437 * NGA-129