When choosing a pre tightening scheme for bolts, it is not simply a matter of considering the cost of the scheme, and not all bolts are suitable for pre tightening with hydraulic wrenches or lithium torque wrenches. The appropriate pre tightening scheme must be determined by the bolt material, specifications, and process, and the choice is not arbitrary.
When selecting hydraulic wrenches, if the pre tightening torque is not known, we usually need to ask the customer about the material strength and specifications of the bolt, and then we can choose a suitable pre tightening plan and tool model for the customer based on the bolt situation. The material directly affects the performance of bolts, such as strength, toughness, wear resistance, and corrosion resistance. Bolts of different materials may require different pre tightening methods and tools during the pre tightening process. For example, high-strength bolts (such as alloy steel bolts) may require the use of high torque output tools such as hydraulic wrenches or electric wrenches for pre tightening; The yield strength of stainless steel bolts is lower than that of alloy steel, and their pre tightening torque is also much lower for the same specifications. Therefore, manual torque wrenches or electric torque wrenches may be suitable for the same specifications.
For the same specifications, higher material strength naturally requires tools that can provide higher torque preload force to achieve good preload effect. Compared to M30 bolts, the pre tightening torque of general structural steel bolts is less than 500Nm. The pre tightening torque of mechanical structural steel materials can reach 700Nm, the pre tightening torque of chromium molybdenum alloy steel materials is 980Nm, the pre tightening torque of nickel chromium molybdenum alloy steel materials is 1570Nm, and the strength level 12.9 can even reach 1882Nm. For materials with low strength, manual torque wrench solutions are more than sufficient. For materials with high strength, dismantling electric torque wrenches is somewhat difficult.