Calculation method and notice of high strength bolt

Bolts made of high-strength steel, which may require a larger preload, can be called Suzhou high-strength bolts. High strength bolts include stainless steel bolts and other bolts, which are mostly used for the connection of bridges, rails, high-pressure and ultra-high-pressure equipment. The cracking of this kind of bolt is brittle. High strength bolts used in ultra-high pressure equipment need to be prestressed in order to ensure the sealing of vessels.
The pretension of high strength bolt is finished by tightening the nut. Torque method, angle method and torsion shear method are generally used.
(1) torque method. Select a special wrench which can flash the torque directly, and apply the torque according to the connection between the torque measured in advance and the bolt tension to make it reach the predetermined pre tension.
(2) angle method. It is divided into two steps: initial tightening and final tightening. The initial tightening is to use a general wrench to make the connected components closely fit each other. The final tightening is to use a powerful wrench to rotate the nut according to the final tightening point recognized according to the bolt diameter and plate stack thickness. When the bolt is screwed to the predetermined view point value, the bolt tension reaches the required pre tension value.
(3) torsion shear method. Twist off the end of the bolt. First, the bolt is initially screwed, and then the two sockets of the special electric wrench are used to separate the nut and the plum head of the bolt. During operation, the large sleeve rotates forward to apply the tightening torque, while the small sleeve applies the tightening torque. After the bolts are tightened, screw off the plum blossom head along the tail slot. Because the notch depth is recognized according to the connection between the final tightening torque and the pre tension, when the plum blossom head is unscrewed, the regular pre tension value is reached.

Quality considerations
(1) rust, oil stain, burr and weld bead on the bolt hole wall shall be cleaned.
(2) the anti scuffing coefficient requirement of the rule should be reached after handling the conflict surface. The high-strength bolts used shall be equipped with nuts and washers, which shall be used according to the matching requirements and shall not be communicated.
(3) the equipment on the conflict surface of the components shall not be stained with oil, soil and other debris.
(4) the conflict surface of components should be monotonous and should not be operated in the rain.
(5) check and calibrate the deformation of the connected steel plate in front of the equipment.
(6) when equipment is used, it is necessary to prevent the bolt from being damaged by hammering.
(7) use the electric wrench with time-saving detection to ensure the accuracy of torque and operate according to the correct tightening sequence.
Primary safety technical measures
(1) the specification of spanner opening should be consistent with that of nut, and it is not suitable to use small spanner to add casing. The dead spanner should be used in high altitude operation. If the live spanner is used, the rope should be used to fasten the safety belt.
(2) when assembling the connecting bolts of steel members, it is forbidden to insert the connection surface by hand or probe the screw hole. When taking and placing the iron pad plate, the fingers should be placed at both ends of the iron pad plate.
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