Expansion screw manufacturer Hilti: The production process error causes the screw pull to decrease

Concealing high-speed rail secondary screws, Australia warning can be killed, accident, MTR refused to disclose details

The MTR was again exposed to the scandal. Hilti, the manufacturer of the explosive screw (expansion screw) involved, issued an engineering warning document to the contractor on April 10, referring to the production of three explosion screws of the "HSL-3 M24" series from May 2011 to August 2013. An error occurred in the production process, which reduced the tension capacity by six to seventy percent, but the shear strength of the screw was not affected.

The exploding screw (expansion screw) involved is about 3 cm in diameter. The longest one is 24 cm long and weighs about 1.4 kg. The retail price ranges from 260 to 298 yuan. It is usually used to fix large components in stone mortar. . The principle of the explosion screw is that when the screw is tightened, the conical component inside will rotate in the opposite direction, and the screw anchor is opened to grasp the stone shovel. The document explains that the problem stems from the lack of a friction coating on the tapered component, which prevents it from fully holding the screw anchor to grasp the stone.