Expansion joint is to compensate for the temperature difference and mechanical vibration caused by additional stress, and set in the container shell or pipe on a flexible structure
Expansion of the screw is generally said that metal expansion screws, expansion screws is the use of wedge-shaped gradient to promote the expansion of friction grip force to achieve a fixed effect. The screw is threaded and has a tapered end. (A steel tube), iron cylinder (steel) half of a number of incisions, put them together into a hole in the wall to fight, and then lock the nut, nut pull the screw out, pull the taper iron cylinder , Iron cylinder was open, so tightly fixed to the wall, generally used for fences, awning, air conditioning, cement, bricks and other materials on the fastening. But its fixed is not very reliable, if the load has a large vibration, may occur loose, it is not recommended for the installation of ceiling fans.