Anti-loosening method of fasteners for rebar connection sleeves
Builders often encounter a variety of problems in the process of ordinary work, among which the loosening of the steel connection sleeve due to the tight connection is one of the most common problems, such a problem if not solved in time, will lead to the safety quality of the building is not up to standard, so it is very necessary to understand the traditional anti-loosening method.
The fastener anti-loosening methods of the rebar connection sleeve specification are roughly divided into the following 4 types:
The first way is riveted punch locking
After tightening, using red spots, welding, bonding and other methods, the function of the moving pair that has lost the thread pair cannot be removed and connected to the connection. The disadvantage of this method is that it is only used once, the bolt rod and removal are very difficult, and you have to destroy the secondary detachable bolt. After tightening, punching, welding, bonding and other methods are used to make the thread pair lose the characteristics of the moving pair and the connection becomes an inseparable connection.
The second way is structural anti-loosening
It is the use of the thread pair itself structure, that is, the Down’s thread anti-loosening method. The Down thread is composed of two spirals, left-handed and right-handed, on the same thread segment, and the Down’s thread has the characteristics of both left-handed and right-handed threads. It can be mated with both left-handed and right-handed threads. Two nuts with different rotation directions are used when joining. The nut on the working support surface is called the fastening nut, and the nut on the non-supporting surface is called the lock nut. When using, preload the fastening nut first, and then pretighten the lock nut. In the case of vibration and shock, the tightening nut will loosen tendency, but because the loosening direction of the fastening nut is the tightening direction of the lock nut, the tightening of the lock nut just prevents the tightening nut from loosening, resulting in the tightening nut cannot be loosened. Tang’s thread fasteners use the contradiction of the thread itself to loosen and restrain the loosening, and play the effect of “attacking the poison with poison”.
The third is friction anti-loosening
This is the most widely used screw pair as a locking device in this way that does not generate friction between the relative rotation of a pair of threads with changing external positive pressure. This positive pressure is achieved by two counter-axial directions or simultaneously to clamp the screws. If you use elastic washers, rebar connection sleeves, self-locking nuts, nylon lock nuts, etc. This means that the removal of the lock nut is more convenient, but in the case of shock, vibration and variable load, the bolt preload decreases due to relaxation, the vibration frequency increases, and the loss of preload slowly increases, which will eventually lead to the nut loosening and connection failure.
The fourth method is mechanical anti-loosening
The plug directly restricts the relative turn of the screw pair. Such as the use of open-tail pins, gasket chain wires, etc. Since the plug does not have a preload nut loose to fall back down to lock the brake position the plug works, therefore, this practice is not practical to lock to prevent loss. It is to use the stop to directly limit the relative rotation of the thread pair. Such as cotter pins, tandem wires and stop washers. Since the stop has no preload, the anti-loosening stop only works when the nut is loosened to the stop position, so this method is actually not anti-loosening but prevents falling off.
Product Recommendation: china nylon nut