Introduction to the usage specifications for bolts, nuts, and washers
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Basic requirements for bolt connections: When ordinary bolts are used as permanent fasteners, they must meet the following requirements: 1. For typical bolt connections, flat washers should be placed under the bolt head and nut in order to increase the load-bearing area. 2. Flat washers should be placed on the bolt head side and the nut side respectively; generally, there should not be more than 2 flat washers on the bolt head side, and no more than 1 flat washer on the nut side. 3. For bolts and anchor bolts designed to prevent loosening, nuts or spring washers with anti-loosening features should be used, and the spring washer must be placed on the side of the nut. 4. For bolted connections that are subject to dynamic loads or are in critical locations, spring washers should be used as required by the design; these spring washers must be placed on the side of the nut. 5. When using inclined joints for I-beams and channel steels, inclined washers should be used to ensure that the bearing surfaces of the nuts and bolt heads are perpendicular to the screw shaft. Classification requirements for bolt usage locations: Based on the location and function of bolts in distribution lines, bolts can be classified into three categories: those used for electrical connections, those used to secure electrical equipment, and those used to fix metal accessories. The details are as follows: 1. Electrical connections: Outdoor primary wiring should be connected using hot-dip galvanized bolts; these bolts must be equipped with flat washers and spring washers. After the bolts are tightened, they should protrude by 2–3 threads. One bolt is equipped with two flat washers, one spring washer, and one nut. During installation, place a flat washer on the side of the bolt head, and a flat washer along with a spring washer on the side of the nut, with the spring washer positioned next to the nut. 2. Electrical equipment fixation: For the connection of transformers, distribution box bases, and iron accessories using inclined bolts on channel steel, one bolt is equipped with one nut, one inclined washer (used on the inclined side of the channel steel), and one flat washer (used on the flat side). When fixing using flat bolts on channel steel, one bolt is paired with two flat washers, one spring washer, and one nut. During installation, place a flat washer on the side of the bolt head, and a flat washer along with a spring washer on the side of the nut, with the spring washer positioned next to the nut. For the connection of isolating switches, drop fuses, arresters, and iron accessories, the installation bolts provided by the equipment manufacturer should be used in principle. 3. Iron accessory fixation type: When the bolt holes for connecting iron accessories are round, one bolt is paired with one nut and two flat washers; when the bolt holes are rectangular, one bolt is paired with one nut and two square washers. During installation, one flat washer (or square washer) is placed on each side of the bolt head and the nut. When double-headed bolts are used for connecting iron fittings, each end of the bolt is equipped with a nut and a flat washer (square washer). For bolted connections on the inclined surfaces of channel and I-beam flanges, inclined washers should be used as much as possible to ensure that the bearing surfaces of the nut and bolt head are perpendicular to the shank. Requirements for the direction of bolt insertion: 1. For three-dimensional structures: horizontally, from the inside outward ； Vertically, from bottom to top. 2. For planar structures: along the direction of the line, for double-sided components, from the inside outward; for single-sided components, from the power supply side or in a unified direction ； In the transverse direction: from inside to outside on both sides, from left to right in the middle (facing the power-receiving side), or in a unified direction ； Vertically, from bottom to top. 3. Planar structure of the transformer test bench: Using the high-voltage and low-voltage terminals of the transformer as reference directions, it extends from the low-voltage terminal side toward the high-voltage terminal side ； Using the transformer and electric pole as reference directions, pass from the transformer side toward the electric pole side (from inside to outside). Requirements for bolt tightening: The connection bolts should be tightened one by one, and the torque required to tighten them should not be less than the values specified in Table 4. If it is found that the threads of the screw and nut are stripped, or that the edges of the nut are worn to the point where the wrench slips, the bolt and nut should be replaced. Table 4: Bolt Tightening Torque Standards – Bolt Assembly 1. Before assembly, visually inspect the bolts, nuts, or the threaded holes of the components to be connected; there should be no dents or scratches, and they must meet the requirements specified in the drawings or the standards referenced in this specification. 2. During assembly, the threaded portion of the bolt must not be damaged. 3. The washer on the head of the bolt and on the nut’s end face should make even contact with the surface of the part being fastened; it should not be tilted, and hammers must not be used to force these two surfaces into contact. The screw rod should not be bent or deformed. 4. The connected parts should be subjected to even pressure, fit closely together, and be firmly connected. 5. It is strictly prohibited to use inappropriate wrenches when tightening bolts and nuts. 6. When assembling bolts and screws, hand-tighten them by more than 2–3 pitches, and then tighten them using a wrench or power tool. 7. When assembling bolts and nuts, be careful to protect the paint coating and plating of the components being connected, as well as the heads of the bolts and nuts, to avoid any damage. 8. After the nut is tightened, the head of the bolt should protrude 2–3 thread pitches beyond the end face of the nut. Both the nut and the washer should have their opposite sides facing the components being connected (the side with inscriptions on the nut is the front side, while the smooth side of the washer is also considered the front side). 9. After the bolts are tightened, apply paint markings; these markings are usually made using red paint at the point where the bolt meets the nut. The color can be changed depending on the location of use, but it must be clearly distinguishable.
Bolts, nuts, and washers are important elements of fasteners, and certain standards must be followed when using them to ensure the reliability and durability of the connections. The following are the basic requirements and specifications for using bolt connections: Basic requirements for bolt connections: 1. When ordinary bolts are used for permanent connections, flat washers should be placed under the bolt heads and nuts to increase the load-bearing area. 2. Usually, no more than two flat washers are placed on the bolt head side, and generally no more than one flat washer is used on the nut side. 3. For bolts that require anti-loosening, such as anchor bolts, nuts with anti-loosening devices or spring washers should be used, with the latter having to be placed on the side of the nut. 4. For bolted connections subjected to dynamic loads or located in critical areas, spring washers shall be used as required by the design, and placed on the side of the nut. 5. When using inclined joints with I-beams or channel steels, inclined washers should be employed to ensure that the bearing surfaces of the nut and bolt heads are perpendicular to the screw shaft. Classification requirements for bolt usage locations: 1. Electrical connections: Hot-dip galvanized bolts should be used for outdoor wiring, along with flat washers and spring washers. After tightening the bolt, 2–3 threads should be exposed. 2. Fixing of electrical equipment: Equipment such as transformers and distribution boxes is fixed using channel steel with inclined or flat bolts, and corresponding washers and nuts are required. 3. Iron attachment fixing type: When the connection holes for iron attachments are round or elongated, washers of different shapes are used to ensure even force distribution. Requirements for the direction of bolt insertion: 1. In three-dimensional structures, horizontally from inside to outside, and vertically from bottom to top. 2. The planar structure should take into account the route direction, the requirements for single and double-sided components, and the intermediate positions. 3. The layout of the transformer test bench structure is determined based on the relative positions of the transformer and the pole. Requirements for bolt tightening: 1. Bolts should be tightened one by one, meeting the torque requirements. 2. If the nuts or bolts are damaged, they should be replaced. Key points for bolt assembly: 1. Check the bolts and nuts to ensure there are no damages. 2. Do not damage the threads during assembly. 3. The washer should make even contact with the surface of the part to be fixed, and the bolt should not be bent. 4. Ensure that the connected parts are evenly compressed and fit tightly together. 5. Use the appropriate wrench to tighten the bolts and nuts. 6. Turn it in manually by pitch, then tighten it with a tool. 7. Be careful to protect the paint film and coating of the connected parts. 8. After tightening the nut, the bolt head should be properly exposed, and attention should be paid to the orientation of the washer. 9. Apply paint markings after tightening. These specifications ensure the structural strength and safety of bolted connections. During implementation, it is also necessary to adjust the types and specifications of components used according to the specific application scenario. .