UNE 36-593-1986 Hollow profiles for mechanical applications. Tubular profile characteristics and measurements for precise internal and external caliber measurement
The products defined in this standard will be designated in the following order, by:
——the letters TP;
——the external diameter and wall thickness (in millimeters);
——the grade of steel composed of the letter A and a three-digit number indicating the minimum tensile strength in the standardized state;
——the state of delivery (see 5.3); the reference to this standard. Example: Precision hollow profile (precision tube), welded in annealed steel grade A 340, external diameter of 25 mm and 2 mm wall thickness.