I. Friction-Based Anti-Loosening Measures
1. Install Matching Washers: Install spring washers or wedge-type double-layer locking washers on the nut's mating surface. The continuous rebound force of the washers maintains the friction between the threads, preventing loosening.
2. Use Self-Locking Lock Nuts: Prioritize nylon insert self-locking nuts and 30° wedge-thread self-locking nuts. These rely on the locking friction between the threads to achieve long-term anti-loosening and are suitable for vibration conditions.
3. Double Nut Counter-Locking: First, screw in the lower thin nut applying 80% of the standard torque, then screw in the upper standard nut applying 100% of the rated torque. The two nuts counter-lock, significantly improving anti-loosening reliability.
II. Mechanical Locking Measures
1. Cotter Pin + Slotted Nut Matching: After tightening the nut, insert the cotter pin into the pre-drilled hole in the nut slot and the bolt tail, fully opening the cotter pin tail to completely restrict the relative rotation of the nut and bolt.
2. Locking Washer: After tightening the nut, bend the single/double lugs of the locking washer tightly against the sides of the nut and connector, directly locking the nut to prevent loosening.
3. Series Wire Restraint: Insert steel wires into pre-drilled holes in multiple bolt heads, connecting all bolts in series to form a mutually restraining structure. Individual bolts cannot loosen independently, often used in high-reliability applications such as aerospace.
III. Chemical Bonding Measures
1. Thread Locking Adhesive Application: Select thread locking adhesive of appropriate strength according to different working conditions. For through-hole applications, apply the adhesive to the thread engagement area; for blind hole applications, apply adhesive to both the bottom of the hole and the bolt threads. After curing, the threaded pair is bonded together, achieving permanent anti-loosening.
2. Applying Special Anti-Loosening Liquid: Evenly apply anti-loosening liquid to the engagement threads of the tightened bolts, then tighten the locking nut. After curing, it fills the thread gaps, significantly increasing the frictional resistance between the threads.
IV. Installation Process Optimization Measures
1. Strictly Control Pre-tightening Force: Tighten to the standard torque corresponding to the bolt specifications, ensuring the pre-tightening force reaches 70%~90% of the bolt's yield strength to avoid loosening due to insufficient pre-tightening force.
2. Regular Re-tightening Inspection: Re-tighten after 48 hours of initial installation and operation. Subsequent inspections should be scheduled based on operating conditions. For high-vibration equipment, shorten the inspection interval to promptly compensate for pre-tightening force loss due to stress relaxation.
3. Avoid Mismatched Use: Do not mix bolts and nuts of different strength grades or materials. Thoroughly clean oil and impurities from the threads before installation to ensure complete thread engagement.
