Bolt Usage Location Classification
Dec 16, 2025
Based on their location and function, bolts in power distribution lines can be categorized into three types: electrical connections, electrical equipment fixing, and iron accessory fixing.
1. Electrical Connections: Outdoor primary wiring should use hot-dip galvanized bolts. Bolts should include flat washers and spring washers. After tightening, 2-3 threads should be exposed. Each bolt should be fitted with two flat washers, one spring washer, and one nut. During installation, place one flat washer on the bolt head side and one flat washer and one spring washer on the nut side, with the spring washer close to the nut.
2. Electrical Equipment Fixing: When connecting transformers, distribution box bases, and iron accessories using channel steel bevel bolts, each bolt should be fitted with one nut, one bevel washer (for the bevel side of the channel steel), and one flat washer (for the flat side). When using channel steel flat bolts, each bolt should be fitted with two flat washers, one spring washer, and one nut. During installation, place one flat washer on the bolt head side and one flat washer and one spring washer on the nut side, with the spring washer close to the nut. For connections between disconnecting switches, drop-out fuses, surge arresters, and iron fittings, the mounting bolts provided by the equipment manufacturer should be used in principle.
3. Iron Fitting Fixing: When the bolt holes for iron fittings are round, one bolt should be fitted with one nut and two flat washers. When the bolt holes are oblong, one bolt should be fitted with one nut and two square washers. During installation, one flat washer (or square washer) should be placed on the bolt head side and one on the nut side. When using double-ended bolts for iron fitting connections, one nut and one flat washer (or square washer) should be fitted on each end of the bolt. For bolt connections on the inclined surfaces of channel steel and I-beam flanges, beveled washers should be used as much as possible, ensuring that the bearing surfaces of the nut and bolt head are perpendicular to the bolt shank.
