This specification covers seamless and electric-resistance-welded steel pipe used as conduit for the installation of high-pressure pipe-type electrical cables in NPS 4 to NPS 12, inclusive, with nominal (average) wall thicknesses 0.219 to 0.562 in., depending on size. The steel shall be made by one or more of the following processes: open-hearth, basic-oxygen, or electric-furnace. Tensile strength tests, flattening test, hydrostatic tests shall be made for the materials to conform the requirements as specified. If the results of the mechanical tests do not conform to requirements specified, retests shall be made.