Torque Calibration and Testing Specification for High-Strength bolts

The reliability of high-strength bolt connections highly depends on assembly torque. Insufficient torque causes loosening and vibration, while excessive torque leads to bolt fracture and thread slipping. Standardized calibration and testing processes are essential for equipment safety.

1. Regular Calibration Requirements for Torque Wrenches

Torque wrenches must be calibrated every 6 months (or 3 months for high-frequency use) by qualified third parties. Uncalibrated tools are not allowed for high-strength bolt assembly.

2. Torque Calculation and Selection Principles

Torque can be calculated by T = K × d × F. The torque coefficient K varies with surface treatment, so use the correct value for black oxide or galvanized bolts. Reduce torque by 15%-25% when using thread adhesive or lubricant.

3. On-Site Assembly and Re-Inspection Standards

Clean threads before assembly and apply force evenly. Carry out re-inspection 24 hours after final tightening, with torque deviation controlled within ±10%. Record all data for traceability.