Calculation method and common problems of high-strength bolts

Calculation method and common problems of high-strength bolts

??Anchor bolts made of high-strength steel plates that may require a large pre-tightening force can be called Suzhou high-strength bolts. High-strength bolts, including stainless steel screws and other anchor bolts, are mostly used for the connection of bridges, rails, high-voltage and high-voltage equipment. The cracking of such anchor bolts is mostly ductile cracking. The high-strength bolts used in high-pressure equipment require a large amount of prestressed reinforcement in order to ensure the tightness of the container.

?? The pre-tensioning force of the high-strength bolts is completed by tightening the nuts. Generally, the torque method, corner method and torsional shear method are used.

?? (1), torque method. Use a specially made wrench that can display the torque directly, and release the torque according to the relationship between the measured torque and the tensile force of the anchor bolt in advance, so that it can reach the pre-tensioned force ordered.

?? (2), corner method. It is divided into two steps: initial screwing and final screwing. The initial screwing is to use a normal wrench to make the connected prefabricated components meet each other tightly. The final screwing is to start from the direction of the initial screwing. According to the final screwing focus recognized by the diameter of the anchor bolt and the thickness of the plate stack, use a strong wrench to turn the nut.

?? (3), torsional shear method. Twist off the osmanthus head at the end of the anchor bolt. First screw to the anchor bolts first, and then use the two socket specifications of the specially made electric wrench to respectively put the nut and the osmanthus head at the end of the anchor bolt. In actual operation, the large socket specification releases the tightening torque forwardly, and the small socket specification releases the tightening reverse torque. After the anchor bolts are tightened, unscrew the sweet-scented osmanthus head along the slot at the end. Since the depth of the slot is determined according to the relationship between the final tightening torque and the pre-tension force, when the osmanthus head is unscrewed from the bolt, the standard pre-tension value is reached.

??FAQs at the quality level

??(1) Surface rust, oil stains, burrs on the edges of anchor bolt holes, welding scars, etc. should be cleaned up.

?? (2) After the contact contradiction is resolved, it must meet the standard scratch resistance index requirements. The high-strength bolts used should have supporting nuts and sealing rings, and they should be used according to the supporting facilities when used, without communication.

(3) Oil stains, soil and other dirt are not allowed to be stained on the contradictory surface of the prefabricated component.

(4) The contradictory surface of the components during equipment should be kept simple and should not work in the rain.

(5) Before the equipment, carefully observe and check the deformation of the connected steel plate.

(6) Stop hammering into the bolts during installation to avoid damage to the bolts.

(7) Check the electric wrench regularly during use to ensure the accuracy of the torque, and operate according to the correct tightening sequence.

??Main safety production technical countermeasures

?? (1) The size of the wrench using the adjustable wrench should be consistent with the size of the nut, and a waterproof sleeve should not be added to the small wrench. Dead wrench should be used when working at high altitudes. If a familiar wrench is used, it should be fastened with a rope, and people should pay attention to safety.

??(2) When assembling steel prefabricated components to connect anchor bolts, it is forbidden to insert the joint surface or probe the screw holes by hand. When picking up the stainless steel plate, the fingers should be placed on both sides of the stainless steel plate.