Basic requirements for bolted connections
When using ordinary bolts as permanent connection bolts, the following requirements should be met:
For general bolted connections, flat washers should be placed below the bolt head and nut to increase the bearing area.
2. Flat washers should be placed separately on the bolt head and nut side. Generally, there should be no more than 2 flat washers placed on the bolt head side, and no more than 1 flat washer placed on the nut side.
3. For bolts and anchor bolts that require anti loosening in design, nuts or spring washers with anti loosening devices should be used, and the spring washer must be set on one side of the nut.
4. For bolted connections that bear dynamic loads or important parts, spring washers should be placed according to design requirements, and the spring washers must be set on one side of the nut.
5. When using inclined connection for I-beam and channel steel types, inclined washers should be used to make the bearing surface of the nut and bolt head perpendicular to the screw.
Classification requirements for bolt usage positions
According to the location and function of distribution line bolts, bolts can be divided into three types: electrical connection type, electrical equipment fixing type, and iron accessory fixing type. Below are specific instructions:
1. Electrical connection type: Outdoor primary wiring should be connected with hot-dip galvanized bolts, and the bolts used should have flat washers and spring washers. After the bolts are tightened, 2-3 buckles of the bolts should be exposed. A bolt is equipped with two flat washers, one spring washer, and one nut. During installation, place a flat washer on the bolt head side, a flat washer and a spring washer on the nut side, with the spring washer against the nut.
2. Electrical equipment fixation: When connecting the base of transformers and distribution boxes with iron accessories using channel steel inclined bolts for fixation, one bolt is equipped with a nut, an inclined washer (for the inclined side of the channel steel), and a flat washer (for the flat side 2). When using channel steel flat bolts for connection and fixation, one bolt is equipped with two flat washers, one spring washer, and one nut. During installation, place a flat washer on the bolt head side, a flat washer and a spring washer on the nut side, with the spring washer against the nut. The connection between isolation switches, drop type fuses, lightning arresters, and iron accessories should generally use installation bolts provided by the equipment manufacturer.
3. Fixed type of iron accessories: When the connecting bolt hole of iron accessories is a circular hole, one bolt is equipped with a nut and two flat washers. When the connecting bolt hole of iron accessories is a long hole, one bolt is equipped with a nut and two square washers. During installation, a flat washer (square washer) is placed on the bolt head side and the nut side respectively. When double headed bolts are used for the connection of iron accessories, each end of the bolt is equipped with a nut and a flat washer (square washer). For bolted connections with inclined surfaces on the flange of channel steel and I-beam, use inclined washers as much as possible to ensure that the bearing surfaces of the nut and bolt heads are perpendicular to the screw.
Requirements for bolt threading
1. For three-dimensional structures: horizontally from the inside out; Vertical direction from bottom to top.
2. For planar structures: in the direction of the line, double-sided components are inserted from the inside out, while single-sided components are inserted from the power supply side or in a unified direction; In the direction of the horizontal line, both sides should be from inside out, and the middle should be from left to right (facing the receiving side) or in a unified direction; Vertical direction, from bottom to top.
3. Transformer rack plane structure: with the high and low voltage terminals of the transformer as the reference direction, threading from the low voltage terminal end to the high voltage terminal direction; Using the transformer and pole as reference directions, thread from the side of the transformer to the pole side (from the inside out).
Tightening requirements for bolts
The connecting bolts should be tightened one by one, and the tightening torque of the bolts should not be less than the provisions in Table 4. If it is found that the threads of the screw and nut have sliding teeth or the edges and corners of the nut are worn, causing the wrench to slip, the bolt and nut should be replaced.
Bolt assembly
1. Before assembly, visually inspect the threaded holes of bolts, nuts, or connected components to ensure they are free from bumps or scratches and comply with the standards referenced in the drawings or this specification.
2. During the assembly process, the threaded part of the bolt must not be damaged.
3. The head of the bolt and the washer on the end face of the nut should be in uniform contact with the plane of the tightened part, and should not be tilted. It is also not allowed to hit the two planes with a hammer to make contact, and the screw should have no bending deformation.
4. The connected parts should be evenly compressed, tightly fitted to each other, and firmly connected.
5. It is strictly prohibited to use inappropriate wrenches when tightening bolts and nuts.
6. When assembling bolts and screws, they should be screwed in by hand with a pitch greater than 2-3, and then tightened with a wrench or electric tool.
7. When assembling bolts and nuts, pay attention to protecting the paint film, coating, and bolt and nut heads of the connected parts from damage.
8. After tightening the nut, the head of the bolt should expose the nut end face for 2-3 pitches. The nut and washer should face the connected body on the opposite side (the side marked with the words on the nut is the front side, and the smooth side of the washer is the front side).
9. After the bolt is tightened, paint the mark with a red paint dot at the contact point between the bolt and nut. The color can be changed according to the usage location, but the color must be clearly distinguished.