Welding must be of material having a melting point in excess of 800 °C (1475 °F) (except that for packages constructed prior to March 31, 1975, this temperature may be 540 °C (1000 °F)), with a joint efficiency of at least 0.85. This requirement applies to welding used in adding spacer rods to comply with § 178.352-3(c)(1).