Why do we choose to preload and loosen bolts with a hollow wrench?hydraulic torque wrench

source:Industry News release time:2022-05-19 Article author:yu Popular:Air band saw

　　In the production process, the bolts and nuts are often too large to be disassembled manually, and the torque of torque wrenches, electric wrenches and pneumatic wrenches is too small. According to the hydraulic transmission system, the hydraulic hollow wrench has stable and reliable torque, and the torque size of the hydraulic hollow wrench is adjustable, which is convenient for adjustment and operation. Therefore, at this time, you will think of a hydraulic hollow wrench, a bolt removal tool.

　　In industrial production, the necessity of threaded connection quality has caused widespread concern. The quality of threaded connection is the basis for ensuring the quality of machinery and equipment and the regular operation of machinery and equipment. Its purpose is to improve the bending stiffness, airtightness, tightness, and ground slip resistance of the joint. Effective manipulation of preload is important to ensure the quality of threaded connections.

　　Since the total load of the thread, the critical pressure load of the connection, the working ability to resist the transverse analysis load and the sealing ability of the connecting surface will cause certain damage according to the preload force of the external thread connection, the preload force is too large or too small. It is dangerous, so the size and degree of the preload force are very important, so that the management of the preload force itself becomes one of the key development trends of the external thread connection.

　　The adverse effects of inappropriate preload personal behavior

　　(1) The foundation pile of the threaded connection is invalid

　　If the threaded connection is over-tightened and the preload is too high, the bolt is likely to break, the connection is likely to be cracked, stuck, twisted or cracked, or the external thread is likely to be disconnected and loosened.

　　A part of the coupling makes the standard part move, separate or loosen

　　For the general bolt intermediate connection that the company undertakes to carry out the lateral analysis load, the pre-tightening force is used to create a positive pressure between the connected parts, and the friction force is used to resist the external load. Therefore, the size of the pre-tightening force can determine its bearing capacity.

　　If the preload is not enough, the coupling will roll, causing the coupling to shift, tilt, wrinkle, and even cut the standard part.

　　For bolted connection under radial load effect, the pre-tightening force causes compressive force on the surface of the joint, and the remaining pre-tightening force after the additional load is the compressive force on the surface of the joint during operation. Insufficient pre-tightening force will cause leakage of the joint, such as the leakage of the working pressure pipe, the leakage of the automobile engine, and even the separation of the two by the coupling. Insufficient preload will continue to cause significant lateral vibration, resulting in loosening of the nut.

　　(3) The bolt is fatigued and damaged

　　Most bolts are ineffective due to fatigue. Although reducing the preload reduces the average total circulatory system load on the bolt, it increases the strength of the increased load. Therefore, most of the overall effect is to reduce the fatigue life of the bolt.

https://greenwayalu.com/cold_forging_series/

　　⑷Expand the cost of maintenance and management of machinery and equipment

　　If the preload is too low, a large number of and/or higher standard parts must be used, and often higher coupling components must be used, thereby increasing production costs. At the same time, the cost of many commodities is proportional to the total number of parts to be installed, so too small preload force will increase the installation cost, manufacturing cost and maintenance cost.