For high torque applications such as ship propeller shafts, rudder devices, gas turbine generators and rollers, super-tight bolts have the following strong advantages: 1 screw hole is easier to machine, bolts do not need to be ground again, screw holes The reaming and honing can also be eliminated, and there is still a freely accessible gap between the bolt and the screw hole without the hidden danger of being bitten/killed. It is easier to disassemble and assemble, and the time required for disassembly and assembly will be greatly reduced compared with conventional bolts. The slip between the flanges is eliminated due to the super tight fit caused by the expansion of the super-tight bolts and the pre-tension between the shafts. Due to the expandability of the super-tight bolts, the flanges can be quickly centered, making the alignment of the axes easier. ? Due to the interchangeability of the over-tight bolts and their reusability, no spare parts are required. The disassembly and assembly of the super-tight bolts can be done with a simple set of hand-operated portable tools. The kit consists of a tensioner with attachment and a hand pump with hose and quick coupling. Working principle of super-tight bolts Super-tight bolts consist of a tapered body with a thread at both ends, an expansion sleeve matched with the tapered body and two nuts. The outer diameter of the expansion sleeve is a cylindrical body, and its size is determined according to the size of the screw hole. Usually, the gap with the screw hole is 0105% 0115% of the diameter of the screw hole. The screw hole does not require a high-precision machining surface, and normal boring Processing enough. First, the bolt is placed in the screw hole, and the bolt is pulled by the tensioner, and the relative displacement between the tapered body and the tapered sleeve is used to achieve a press-fit state between the expansion sleeve and the screw hole. The nut is attached to the bolt, the bolt is stretched by the reaction force of one nut, and the other nut is screwed by hand. After the tension of the tensioner is released, the pre-tightening force acts on the bolt. The pre-tightening force will cause a slight decrease in the diameter of the bolt, but the over-expansion of the expansion sleeve can compensate for the reduction of the section of the bolt. The expansion of the sleeve and the stretching of the bolt are done with a special set of stretchers, which must be handled with extreme care. The removal of the bolt can be achieved by pressing the oil into the cone through an oil hole provided in the center of the bolt.

A pressure gauge mounted on the hand pressure to precisely control the amount of expansion and the tensile force. Assembly of the super-tight bolts As shown, the first step is to insert the super-tight bolts into the screw holes of the coupling. Because of the proper clearance between the bolts and the screw holes, it is easy to push in by hand. Configuration. Generally, the number of bolts is usually not less than six. The maximum shear stress of the super-tight bolt is designed to be 280N/mm2; the maximum inter-axial stress is 350N/mm2.

Design torque. The design torque is determined according to the following formula: TD=TN@S where TN is the normal torque and the alternating coefficient S is checked. The number of overtightening bolts. First assume a bolt size, and then determine the E: E = d3 + DD + 10 where d3 is the shaft diameter; DD is the outer diameter of the hydraulic tensioner; E is the screw hole center distance. Calculate the maximum shear force according to the selected bolt size: k1=280P@d214@a where d1 is the super-tight bolt hole diameter; a is the flange material coefficient. If the number of bolts calculated is less than 6, select a smaller bolt and repeat the calculation. The outer diameter of the flange. The outer diameter of the flange is determined by the following formula: D1 = E + 1.6d1 where D1 is the outer diameter of the flange. The calculation method used in combination.

When using super-tight bolts in combination with ordinary bolt bolts, follow the steps below to determine the number of super-tight bolts and common bolts. The design torque is determined according to the formula (1). Select the overtightening bolt size and determine the bolt hole center distance according to equation (2). The number of coupling bolts should be a multiple of the super-tight bolts. Select an appropriate number of super-tight bolts. In principle, no less than 3 calculations of the torque transmitted by the super-tight bolts: TS=n1E210-3(k1+k2@b1@0.5) (6) Determine the torque transmitted by the bolt to be connected according to the following formula: TT = TD-TS (7) where TS is the torque transmitted through the super-tight bolt. According to the following formula, determine the number of bolts n2:n2=TT@2k3@b2@@103(8) where k3 is the tensile force of the bolt; b2 is the bolt prestress coefficient=0.8. (6) flange material coefficient a.

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