How Should The Bolts Be Tightened?

Bolt tightening is a crucial operation that applies torque to create preload on the bolts, ensuring a secure connection. Specific methods include the following steps and key technical points:

Torque Control Method:

Use a torque wrench and set the target torque value according to the bolt's performance grade (e.g., 8.8) and diameter (e.g., 30mm). For example, the typical torque range for an M30 bolt is 900-1200 N·m (refer to specific standards).

Stage Tightening: First, preload with 50% of the target torque, then gradually increase to 100% to avoid uneven stress.

Angle Control Method:

Tighten by hand to the mating surfaces, then rotate with a wrench to a specified angle (e.g., 90°-180°). Suitable for applications requiring high plasticity.

A lubricant is needed to reduce the impact of friction.

Hydraulic Tensioning Method:

Apply axial tension directly to the bolt using a hydraulic tensioner. Suitable for large equipment (e.g., subway segment connections), offering high precision but at a higher cost.