A calibrated wrench connection is a method used to tighten bolts in structural steel connections using a torque wrench calibrated to a specific torque value. It ensures that the bolts are tightened to the required preload and provides a reliable and controlled method of achieving the desired tension in the connection. This method is widely used in construction to ensure the integrity and safety of bolted connections.
Here is a step-by-step procedure for making a calibrated wrench connection:
- Design and Preparation:
- Determine the required bolt preload and load-bearing capacity for the connection based on the structural requirements.
- Select the appropriate high-strength bolts, nuts, washers, and other connection components based on the design specifications, considering factors such as material strength, size, and corrosion resistance.
- Ensure that the surfaces of the steel components to be connected are clean, smooth, and free from any debris, rust, or paint.
- Alignment and Positioning:
- Position the steel components, such as beams, columns, or plates, in their designated locations, ensuring proper alignment and fit.
- Use temporary clamps or tack welds to hold the components in place, preventing movement during the connection process.
- Marking and Drilling:
- Mark the positions for the bolt holes on the steel components, following the specified spacing and pattern.
- Use a drill press or portable drilling machine to drill holes through the marked positions on the components. Ensure that the holes are aligned and perpendicular to the surface.
- Deburring and Cleaning:
- Remove any burrs or sharp edges around the drilled holes using a deburring tool or file.
- Clean the holes and surfaces of the components to remove any debris, oil, or grease that may affect the connection’s integrity.
- Inserting Bolts:
- Insert high-strength bolts through the holes in one of the components.
- Place washers and nuts onto the exposed ends of the bolts.
- Snug Tightening:
- Use a suitable wrench or impact wrench to snugly tighten the nuts until they are in contact with the washer and the joint is fully closed.
- Calibrated Torque Wrench:
- Select a torque wrench calibrated to the specified torque value for the connection.
- Set the torque wrench to the required torque value according to the manufacturer’s instructions or design specifications.
- Torque Application:
- Attach the calibrated torque wrench to the nut of the bolt.
- Apply a slow and steady force to the torque wrench in a clockwise direction until the wrench clicks or signals that the desired torque has been reached.
- Avoid sudden or jerky movements that could result in inaccuracies.
- Final Inspection:
- Inspect the connection to ensure that the bolts, nuts, and washers are properly seated and tightened.
- Check for any gaps, misalignment, or visible signs of damage or distortion.
- Verify that the specified torque value has been achieved for each bolt in the connection.
Example and Application: An example of a calibrated wrench connection is the connection between steel members in a building frame or structural support system. Calibrated wrench connections are commonly used in applications where controlled bolt preload is critical for the structural integrity and safety of the connection.
Applications of calibrated wrench connections include:
- Building construction, where calibrated wrench connections are used to join steel beams, columns, and other structural components.
- Industrial structures, such as manufacturing facilities or power plants, where calibrated wrench connections are employed to connect steel components subject to significant loads, vibrations, or dynamic forces.
The use of calibrated wrench connections provides advantages such as accurate and controlled bolt tightening, compliance with design requirements, and repeatable results. It ensures the structural stability and reliability of bolted connections in various construction and industrial settings.
