Hydraulic torque wrenches need to be calibrated for torque accuracy after a year or thousands of uses. So what are the calibration methods of hydraulic wrenches, and what are the advantages or disadvantages of each method? TorcStark will now detail several calibration solutions for hydraulic wrenches.

Calibration by a third-party testing agency

Calibration and testing of hydraulic wrenches by a third-party professional testing organization are one of the best methods. Testing institutions generally give national-level testing certificates, which are very reliable testing methods. For example, Beijing 304 (under China Aerospace Corporation) and Shanghai 704 (under CSSC) are professional third-party testing institutions in China.

The disadvantage of this method is that the detection is charged according to the detection quantity of the hydraulic wrench, and the size of the torque value of the different wrenches also affects the detection cost. Hydraulic wrenches with higher torques require larger torque sensors and therefore cost more. And the detection period is relatively long.

Calibration via hydraulic wrench torque calibration equipment

If your hydraulic wrenches are used frequently and in large quantities, purchasing a torque calibration device is the most economical and labor-saving method. Torque calibration equipment can be purchased from the hydraulic wrench manufacturer, because each brand of the wrench is slightly different, and it is the best choice to use the original factory for the corresponding torque calibration equipment.

The disadvantage of this method is that it is time-consuming, because each wrench needs to be tested multiple times, and then the value is recorded for calculation. Also, manual calculation of reading values may affect the accuracy of the calibration.

The steps for testing hydraulic wrenches using torque calibration equipment are as follows

Before the hydraulic wrench is calibrated, the indicator of the standard device should be adjusted separately, and the torque value (the corresponding pressure value on the pump station) of the hydraulic wrench needs to be calibrated. According to the size of the hydraulic wrench driving the square shaft (sleeve), select the adapter used to connect it. Carefully check whether the oil pipe of the manual high-pressure pump and the quick connector is connected reliably and whether there is oil in the pump. Connect the standard torque sensor, workbench machine adapter and hydraulic torque wrench, and fix them on the same axis. After confirming that the hydraulic wrench is in the calibration direction, the reaction fulcrum must be found to be safe, reliable and stable. Then start loading to calibrate it according to the detection process.

Put the hydraulic wrench and torque sensor on the torque verification workbench. Connect the three with the connecting shaft and the conversion joint. During the connection process, you must pay attention to make the worktable firm and stable, and keep the torque sensor and the torque axis of the hydraulic wrench horizontal and strictly require coaxiality. After adjusting the mutual position, fix the support arm end of the hydraulic wrench firmly to the work surface to ensure that the two do not move in a mutual position during the process of applying force to the hydraulic wrench.

Correctly select the range of the standard torque sensor according to the rated torque value of the hydraulic wrench, and adjust the zero position of the pressure gauge of the standard device and the hydraulic wrench respectively before installation. Correctly install the hydraulic wrench on the standard device, and then smoothly apply it to the rated torque value step by step according to the selected verification point, read and record the torque value of each point, and this process is carried out at least three times. After each application to the rated torque value, remove the load, check the zero position of the standard unit and hydraulic wrench indicator, and re-adjust the zero position.

Detection via smart socket

The Smart Socket is an advanced torque tool combined with a custom socket with a sensor that accurately detects the final torque applied to the bolt. Therefore, intelligent adjustment can be used to detect the torque accuracy of hydraulic wrenches.

There are three very intuitive buttons on the smart sleeve, which can select the corresponding function and display it on the screen. The outer dimension of the smart sleeve is not larger than that of the ordinary sleeve, which can completely replace the standard sleeve currently in use, and adds the function of torque precision detection and control. The above features make it a tool that can be used for bolt torque detection and torque tool calibration.

The smart sleeve has built-in Bluetooth, allowing real-time data to be viewed on a smartphone or tablet via Bluetooth transmission.

The disadvantage of this method is that it requires a custom sleeve, which may be expensive.

Detection by manual calculation

This solution is developed based on the principle of hydraulic wrench calibration. The core point is to record the pressure value of the wrench pump and the torque value output by the hydraulic wrench and conduct multiple tests and records. Then convert the pressure value of the pump according to the pressure-torque comparison table. Compare the two torque values to calculate the difference.

The pressure value of the pump can read the setting value of the hydraulic gauge. The torque output of the hydraulic wrench can be read using a tool with a torque county display.

The calculation formula is
(standard torque value – actual output torque value of hydraulic wrench) / standard torque value*100%≤3%

The disadvantage of the above method is that it cannot achieve very accurate calculations, and this method is only suitable for projects that do not require high torque accuracy.


The above is an introduction to the calibration method of hydraulic torque wrenches, as well as the advantages and disadvantages. If you have any questions about hydraulic wrenches, please contact us.