How to judge whether the Stainless Steel Hexagon Bolts With Flange need to be retightened?

During long-term use, Stainless Steel Hexagon Bolts With Flange may become loose due to factors such as vibration, temperature changes or material fatigue. Visual inspection is the simplest and most direct judgment method and is suitable for daily maintenance. First, observe the fit between the flange surface and the connected part. Under normal circumstances, the flange surface should be completely fitted without visible gaps. If a gap is found between the flange and the fastener, or the bolt head is obviously skewed, it may have loosened. In addition, check the bolt head and threaded part. If the hexagonal head has rotation marks or the exposed part of the thread is increased compared to the installation, it indicates that the bolt may have loosened. Finally, check whether the flange surface has deformation, indentation or cracks. If these phenomena exist, it means that the bolt may fail due to long-term uneven force.
Torque detection is a more accurate judgment method and is suitable for occasions with high tightening requirements. Use a torque wrench to apply a slight reverse force to the bolt and observe whether it is easy to turn. Under normal circumstances, the bolt should maintain the original preload and will not turn easily. If the bolt can be rotated by applying force lightly, it means that the preload has decreased and needs to be retightened. In addition, the initial installation torque value can be compared. If the measured torque is lower than 70%~80% of the initial value, it indicates that the bolt has loosened and needs to be retightened.
During the operation of the equipment, vibration and noise are effective indicators for judging whether the bolt is loose. A preliminary judgment can be made through a tapping test: tap the bolt head with a non-metallic tool. Under normal conditions, a crisp sound should be emitted without abnormal vibration; if the sound is low, hollow, or accompanied by a sense of vibration, it may be loose. In addition, when the equipment is running, if abnormal noise or high-frequency vibration occurs at the bolt connection, it also indicates that the bolt may be loose and needs further inspection.
For occasions with high precision requirements, more advanced detection methods can be used. Ultrasonic bolt detectors can determine whether the bolt is loose by measuring the elongation or stress change of the bolt, which is suitable for monitoring key parts. In addition, smart gaskets or strain gauges with sensors can be used to monitor the preload change of the bolt in real time, and issue early warnings through wireless transmission technology to achieve intelligent management.
The use environment of Stainless Steel Hexagon Bolts With Flange has a great influence on their tightening state. In high or low temperature environments, the bolts may change their preload due to thermal expansion and contraction, and need to be checked regularly. In a corrosive environment, the threads or flange surfaces may rust, reducing friction and increasing the risk of loosening. Therefore, under harsh working conditions, the inspection cycle should be shortened and anti-rust measures should be taken.
To ensure the long-term and reliable use of bolts, the following maintenance measures are recommended: regular inspections, use anti-loosening measures such as anti-loosening washers, thread glue or double nuts to reduce the probability of loosening. If the bolt head or flange is severely deformed or the thread is damaged, it should be replaced in time to avoid equipment failure or safety accidents due to bolt failure.