Bolt tightening torque

According to the national standards, it’s around 10,000 NM; Siemens recommends 17,000 NM, so there’s a significant difference

The tightening torque for bolts needs to be determined based on various factors such as the bolt specifications, the friction coefficient of the threads, and the loads applied. Typically, engineers determine the most suitable tightening torque based on relevant standards or the manufacturer’s recommended values. However, the actual tightening torque also needs to take into account factors such as temperature, pressure, and the properties of the bolt material. The tightening torque value for large bolts such as the M70 cannot be found in standard literature; it usually needs to be determined through experiments, calculations, or specific guidance from the manufacturer. However, a general calculation method can be provided for reference: The general formula for tightening torque is: \ Where: – \( T \) is the tightening torque (usually in Newton-meters, Nm). - \(K) is the coefficient of friction; depending on the lubrication conditions, and in the absence of specific data, its value may range from 0.1 to 0.3. - \(D) is the bolt diameter in millimeters; in this case, it is 70 mm. - \(P) is the preload, which needs to be calculated or measured. Under high temperature and high pressure conditions, the calculation of preload requires taking into account various complex factors such as the elastic moduli of the bolts and flanges, their expansion coefficients, and the deformation they experience under stress; finite element analysis (FEA) software is typically used for simulation to ensure accuracy. Due to the significant impact of high temperatures of 525 degrees Celsius and operating pressures of 98 MPa on the properties of materials, the performance of alloy steel such as 25Cr2MoV at high temperatures (such as yield strength) declines, and this requires accurate assessment using engineering data. Under such conditions, standard torque calculations may no longer be applicable, and adjustments need to be made based on the actual operating conditions and material properties. The final tightening torque value should be determined by a qualified engineer based on relevant standards, experience, and the requirements of the actual equipment, and it may need to be verified through experiments. If there is not enough data and experience to determine this value, it is advisable to consult the relevant equipment manufacturers or use professional design software for accurate calculations. It is not recommended to calculate and apply bolt tightening torque on your own without the guidance of a professional engineer, as this may lead to unstable connections or equipment damage. .

The manufacturer uses imported materials; 9000 is recommended. We have switched to domestic materials.

The manufacturer is Nimonic80, and it is in the form of studs. The domestic version is 25Cr2MoV, with full threads.