Key Considerations for Bolt Pre-tightening Technology in the Nuclear Power Sector

Bolt pre-tightening in nuclear power plants demands extreme precision and safety; even minor errors can lead to severe consequences. This article details key technical requirements and precautions for bolt pre-tightening in the nuclear sector, helping professionals improve operational quality and safety.

I. Special Requirements for Nuclear Power Bolt Preloading

Bolt preloading in nuclear power plants differs significantly from conventional industrial applications, primarily in the following aspects:

• Nuclear safety-grade requirements with exceptionally strict quality standards.
• Torque accuracy requirement: ±2%; critical areas require ±1%.
• Data must be complete and traceable; records are retained for up to 30 years.
• Tools must be nuclear-grade certified, and materials must meet radiation protection requirements.
• Operators must be professionally trained and certified.

2. Tool Selection and Calibration

Nuclear power bolt tightening must use specialized tools and undergo regular calibration:

• The hydraulic torque wrench must have a nuclear-grade certification.
• Calibration interval must not exceed 6 months. Calibration is mandatory before use of critical components.
• The calibration report must include a complete traceability chain.
• Perform visual inspection and functional testing before using the tool.

3. Key Points for Pre-tightening Process

Proper tightening is critical to ensuring the quality of bolted joints:

• Use staged pre-tightening to gradually reach the target torque in 3-5 steps.
• Use synchronous tightening technology to ensure even load distribution on the flange face.
• Record torque and angle values for each preload.
• After preload is complete, recheck torque. If the deviation exceeds 3%, re-preload.

IV. Data Logging and Traceability

Complete data records are a critical step in nuclear power bolt pre-tightening.

• Record bolt number, specification, material, and other details.
• Record preload date, operator, tools used, and other details.
• Record torque, rotation angle, and oil pressure values for each preload.
• Create a complete torque data archive with both electronic and paper backups.

V. Safety Precautions

Nuclear power bolt tightening operations must strictly adhere to safety regulations:

• Check radiation dose before starting work to ensure it is within safe limits.
• Wear appropriate personal protective equipment (PPE).
• Strictly adhere to the work permit system
• Assign a dedicated supervisor to ensure safe operations.

Pre-tightening nuclear power bolts is a highly technical and rigorous task requiring practitioners with solid expertise and extensive hands-on experience. Alansheng Technology provides nuclear-grade hydraulic torque tools and comprehensive training services to help customers improve the quality and safety of bolt pre-tightening operations.