This standard specifies the structural dimensions and technical requirements for equal-length double-ended studs for pressure vessel flanges. This standard is applicable to JB/T 4701-2000 "Type A Flat Welding Flange", JB/T 4702-2000 "Type B Flat Welding Flange" and JB/T 4703-2000 "Long Neck Butt Welding Flange", etc. Long double-ended studs are also suitable for equal-length double-ended studs used in other non-standard pressure vessel flanges.