厚壁管(①Light tubes shall be welded, medium and heavy tubes and all sockets may be either welded or seamless at the option of the manufacturer. 薄壁管应是焊接的,中厚和厚壁管以及所有的管接头可以是焊接的或无缝的。由厂商选择。② Three thicknesses of tube are provided for as specified in Tables 1, 2 and 3 and are designated light, medium and heavy. 管子的三种壁厚按表 1、2、3所列,分别标明薄壁、中厚壁和厚壁。)