How to Calibrate a Weighbridge

Like any scale, a weighbridge needs regular calibration to ensure accurate measurements and compliance with industry regulations, such as Chain of Responsibility.

There are many steps involved in weighbridge calibration, with extra equipment and precautions required, due to the weighbridge’s large size, exposure to the environment, and heavy-duty situation. Interested to learn more? Keep reading this article to find out.

Step 1: Preparation

• Cleanliness: Clean the weighbridge platform thoroughly to remove debris, dirt, and any potential sources of interference. Due to weighbridges living outdoors on site, it is common for a build up of debris to occur and interfere with the weighing process.
• Zero Check: Verify that the weighbridge is at zero balance with no load on the platform.

2. Initial Assessment
   

• Functional Check: Test all components of the weighbridge, including load cells, junction boxes, and indicators, to make sure they are functioning correctly.
• Software Check: If the weighbridge is integrated with software, ensure the software is updated, with no errors or functionality issues.

3. Calibration Setup
   

• Select Calibration Weights: Choose certified calibration weights that cover the range of expected weights for the weighbridge. These weights are traceable to an international standard and the procedures of testing the weighbridge following the NMI’s National Instrument Test Procedures.
• Positioning Weights: NWI Group utilise a forklift or crane to carefully place the calibration weights on different sections of the weighbridge platform to simulate various loads.

4. Conducting Calibration

• Load Application: Apply the calibration weights sequentially across the weighbridge platform. Ensure each weight is placed accurately on the designated areas.
• Recording Readings: Record the weight readings displayed on the weighbridge indicator for each calibration weight applied.
• Adjustments: If discrepancies are noted between the applied weight and the displayed reading, make necessary adjustments to the weighbridge calibration settings.

5. Verification

• Repeat Tests: Perform multiple tests with different calibration weights to verify consistency and accuracy across the weighbridge platform.
• Documentation: Document all calibration tests, adjustments made, and the results obtained during the calibration process.

6. Finalisation

• Calibration Certificate: Once all tests are successfully completed and adjustments are finalised, issue a calibration certificate. This certificate should include details of the calibration process, results, and the date of calibration.
• Maintenance Schedule: Establish a regular maintenance schedule for the weighbridge to ensure ongoing accuracy and reliability. This may include periodic recalibration based on usage and environmental factors.

7. Compliance and Standards

• Regulatory Compliance: Ensure the calibration process adheres to industry standards and regulatory requirements, such as the National Measurement Regulations.

What happens with the accuracy is off for the weighbridge?

When the accuracy of a weighbridge is off, several issues can arise that impact its functionality and reliability, which means that identifying the problem is crucial. The issue could stem from a variety of reasons, such as load cell damage, loose connections, or even an error with the weighing indicator.

In the instance that your weighbridge calibration is off, NWI technicians will follow a series of steps to troubleshoot the problem.

• Verify the Calibration Issue: Repeat weighing tests using certified calibration weights to confirm the accuracy discrepancy. Check to see if the weighbridge indicator or measurement system consistently shows incorrect readings.

• Inspect Load Cells and Components: NWI technicians will inspect the loadcells and other electronic components for any physical damage, corrosion, or loose connections in the load cells, junction boxes, cables, and other components. Checking all parts are securely mounted and maintained is an important part in troubleshooting the weighbridge.

• Zero Adjustment: NWI technicians will perform a zero adjustment to ensure the weighbridge returns to a true zero balance when no weight is applied. This recalibration step is necessary for eliminating any offset in the measurements.

• Check Environmental Factors: Another important factor to consider is any environmental factors that may be impacting the weighbridge, such as temperature fluctuations, humidity levels, and vibration sources that could affect the weighbridge’s accuracy. Mechanical shock is something that is not considered, and can come from nearby machinery or traffic vibrations, for example.

Depending on the findings, steps should be taken to mitigate these factors if they are contributing to calibration errors.

• Calibration Adjustment: If discrepancies persist after basic/environmental checks, adjust the calibration settings using the weighbridge’s calibration procedure. This typically involves modifying parameters such as sensitivity, zero point, and linearity correction factors to minimise any discrepancies observed.

• Documentation: Once the issue has been resolved and accurate calibration is restored to the weighbridge, our NWI technician will document the entire calibration process. This documentation includes details such as the initial discrepancy observed, adjustments made, verification results, and any other relevant notes.

To conclude this article, we’ve discovered how weighbridge calibration and maintenance is an extremely important part of your yearly routing to guarantee the longevity of your investment. NWI Calibration can help you to set in place a regular calibration schedule to ensure your weighbridge is always compliant, as well as tips and training on how to best keep your weighbridge clean and identify issues before they grow to become a more serious problem.

If you need some advice on your weighbridge calibration, contact us today to talk to one of our experienced calibration technicians.