The national standards for stud bolts have very clear requirements on the selection, production, inspection and packaging of stud screws. Gurent Machinery strictly implements these standards and will process and manufacture in accordance with different industry standards according to different industry uses. For example, the petrochemical stud bolts are manufactured by Gurent Machinery according to petrochemical industry standards HG20613 and HG20634. We use high-quality high-strength alloy steel as raw materials and strictly follow the standards and regulations to produce. When leaving the factory, we have a completely independent and rigorous inspection department for factory inspection. Ensure product quality.
1. The reason for the construction of this article refers to the situation that the space is too small for design reasons to use a special wrench for final tightening. In the construction of torsion shear type high-strength stud bolts, due to the installation sequence and installation direction, the installation direction is not considered properly, or the final tightening Because he is not proficient in the use of electric wrenches. As a result, the ridge ends on the tail plum blossom head are slippery (that is, slipping) during the final screwing, and the plum blossom head cannot be unscrewed, resulting in an unknown final screw torque. A certain proportion should be controlled for such bolts.
2. Factory direct sales of high-strength stud bolts are first tightened, and the purpose of re-tightening is to make the friction surface close and the bolts are evenly stressed. For large nodes, the installation sequence is emphasized to prevent uneven bolt pretension loss in the nodes and affect the connection The stiffness.
3. Forcibly penetrating the bolt will damage the thread, change the torque coefficient of the high-strength stud bolt connection, and even the nut can not be screwed, so it is emphasized that the bolt hole is freely penetrated, and the gas cutting reaming is very irregular, which weakens the component The effective load surface of the slab reduces the pressure transmission area and also causes defects in the steel at the reaming. Therefore, it is stipulated that gas cutting and reaming are not allowed. The maximum reaming amount is also based on the consideration of the effective load surface and friction force transmission area of the component.
4. For the bolted ball joint grid, the stiffness (deflection) is often weaker than the design value. The main reason is that the high-strength stud bolts connecting the bolt ball and the steel pipe are not fastened firmly, and there is a gap, looseness and other untightened conditions. When the lower support system is removed, due to the connection gap, looseness and other reasons, the deflection is significantly increased, exceeding the limit specified by the specification.