Copper pipes are in accordance with the EN13348 standard and with DIN 1786 and DIN 17671, type R290 (SF Cu F37), arsenic free, oil free, protected to their ends, characterized according to the regulations for use in medical gases installations using silver welding of 40% content in silver, in neutral gas (N2) environment. The pipe flections are permitted up to diameter of 18mm according to the standard EN13348 and regulations DIN 1786 by using a special tool.