Reason for Subway Bolt Fracture
1. The metro bolt manufacturing process is unreasonable, leading to bolts failing to meet standard requirements within a short period or exhibiting original cracks in the products, which can cause them to break when in use.
2. Issues with the material of subway bolt fasteners, or defects in processing and heat treatment techniques, can lead to the failure of fastener bolts in high-speed, heavy rail, subway, and light rail tracks. To avoid such problems, collaborate with a service rail component company, reduce the rate of defective products, or conduct thorough inspections before use.
3. The bolt design for the subway meets national standards, but the fatigue strength is difficult to meet the actual working conditions. The bolt connection design is unscientific and cannot achieve the required tightening torque.
4. The subway bolt staff is unprofessional. During assembly, they apply excessive torque and uneven force. Many people believe that the bolts are properly tightened, but if the torque is too high, exceeding the yield limit of the bolt material, it can cause yielding deformation in the connecting rod bolts, leading to breakage due to excessive elongation under impact loads. Installation personnel for high-speed rail, heavy rail, subway, and light rail track fasteners must tighten the connecting rod bolts according to standards and should never assume that more force is better.
5. The subway bolt material was substandard, with severe non-metallic inclusions in the steel, which became the source of fatigue cracks.
6. Metro bolt fatigue or impact fracture. High-speed rail, heavy rail, metro, and light rail track fasteners, such as bolt fasteners, are subjected to various vibrations and impacts from the high-speed trains daily. Over time, this can lead to fatigue life fractures. During operation, fasteners under axial force experience thread damage and the bolt breaks. Under radial force, bolts are sheared and bolt holes are deformed into oval shapes. These are common types of fractures.
Method to Prevent Rail Bolt Fracture in Subway
1. Bolts for the subway should be handled with care during transportation, storage, and use to prevent thread damage. Bolts with severe thread damage or those that have been exposed to rain should not be used.
2. Please avoid opening the box of the subway bolts before use to prevent damaging the packaging's sealability. After removing some bolts from the box, re-seal the packaging to prevent them from getting dusty or rusty.
3. Subway bolt connection sets should be supplied by the manufacturer in a complete set, with each packaging box containing bolts, nuts, and washers. The packaging box should meet storage and transportation requirements and possess waterproof and sealing functions. The packaging box should also include a product specification sheet and a quality guarantee certificate; the exterior of the packaging box should be marked with batch number, specifications, and quantity.
4. During the installation and use of subway bolt connections, what are subway bolts? The construction site should collect the specified specifications and quantities of bolts as planned for that day. Any bolts remaining after installation on that day should be properly stored, and if possible, they should be returned to the warehouse for storage.
5. The bolt connection sets for the subway should be stored in boxes in an indoor warehouse, with moisture-proof measures on the ground. They should be sorted by batch number and specifications and not mixed during storage and use. The packaging boxes of the bolt connection sets should be placed on the ground level with an air gap, with the copper-linings high-speed rail bolts being elevated more than 3CM from the ground. The stacking height should generally not exceed 5-6 layers.
6. Whether the surface treatment of the subway bolts meets the relevant standards and requirements of the procurement contract; compliance is considered合格, non-compliance is deemed不合格.
