Fasteners without rivets are common parts. Some mechanical equipment must work at high temperatures, such as boilers and steam turbines. As a result, mechanical fasteners are also affected by high temperatures, which affect their performance. malfunction. The following measures should be taken when the fastener is used at high temperatures.
1. Sealing stress: ensuring the tightness of the connecting parts is a basic requirement for bolting. In the case where the geometry of the flange, the processing quality of the joint surface, the pressure of the steam and the temperature are constant, the sealing stress is determined by the tightening force of the bolt.
2. Temperature stress: When the unit is started and running, due to the temperature difference between the flange and the bolt, and the linear expansion coefficient of the two materials, the free thermal expansion of the flange is larger than the bolt, and the bolt receives an additional pulling force. The stress caused by this additional pulling force in the bolt is called temperature stress.
3. Hot tightening of bolts: Bolts that are subjected to pre-tightening force during installation. When the pilot is running, under the action of steam pressure, the bolts are forced to increase more than the initial preload force. For general horizontal flanges. The bolt tension is increased by 5%-15%, so that the initial stress of the bolt can be lower than when it is cold.
No matter what method is used to tighten the mechanical equipment to prevent malfunctions, it is necessary to understand the measures of the fasteners when working at high temperatures to avoid the failure of the performance of the fasteners, resulting in accidents.
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