Hydraulic wrench have extremely high requirements for torque accuracy, so each hydraulic torque wrench will undergo strict torque calibration before leaving the factory. How does the user personally perform the torque calibration?

Now, TorcStark will go into detail.

What is Hydraulic Torque Wrench Calibration?

Hydraulic torque wrench calibration is to use professional torque calibration equipment to test whether the torque value output by the hydraulic wrench when the hydraulic pump provides stable pressure is consistent with the value on the hydraulic wrench torque conversion chart, so so to ensure that the hydraulic wrench can output a stable torque during work to achieve the rated torque value of the bolt.

Why do you need a hydraulic torque wrench calibration?

50% of accidents in the world are caused by problems with bolts. As a high-precision bolt tightening tool, the hydraulic wrench has unparalleled advantages in disassembly and assembly of threaded connections and control of pre-tightening force. It is widely used in industrial production and infrastructure construction. In order to ensure the quality of industrial projects and the safety of construction workers, hydraulic wrenches require a torque calibration after 5,000 bolt removals or one year of use, so that problems with hydraulic wrenches can be found in time and repaired or replaced.

Hydraulic torque wrench calibration requirements

1. Torque calibrator, pressure-torque conversion chart of the calibrated hydraulic wrench

2. Before the calibration, the zero position of the indicator of the standard device and the torque value to be calibrated for the hydraulic wrench (the corresponding pressure value on the pump) should be adjusted respectively.

3 According to the size of the hydraulic wrench square drive shaft (socket), select the adapter used to connect it.

3. Carefully check whether the quick joints of the manual high-pressure pump oil pipeline are connected reliably and whether there is oil in the pump.

4. Connect the standard torque sensor, workbench machine adapter and hydraulic torque wrench, and fix them on the same axis.

5. After confirming that the hydraulic wrench is in the calibration direction, find the reaction fulcrum, which must be safe, reliable and stable.

6. Then start loading and calibrate it according to the calibration procedure.

Hydraulic torque wrench calibration standard

1. There is a certain relationship between the calibration cycle and the frequency of use of hydraulic wrenches. TorcStark recommends here: Generally, after 5,000 bolt removals or one year of use, it is necessary to calibrate once.

2. During the detection process, correctly select the range of the standard torque sensor according to the rated torque value of the hydraulic torque wrench. Then apply it to the rated torque value step by step according to the selected verification point, read out and record the torque value at each point, at least 3 times per procedure. Remove the load after each application to the rated torque value, check the zeroing of the standard unit and the hydraulic torque wrench indicator and re-zero before continuing.

Hydraulic wrench calibration procedure

1. Select the appropriate reaction arm and appropriate joint according to the range of the hydraulic wrench, and carefully connect the hydraulic oil pipe to ensure that it is safe and reliable without loosening.

2. Put the protective cover on the hydraulic wrench to prevent the parts of the hydraulic wrench from flying out after breaking.

3. Open the operating software of the hydraulic wrench verification device, and set parameters such as range, calibration point, and acquisition times.

4. Turn on the hydraulic pump of the hydraulic wrench calibration device, pressurize slowly, and observe the output torque value until the calibration is completed.

5. After the calibration is completed, remove the hydraulic wrench and hydraulic oil pipe in reverse order according to the original steps.

6. The hydraulic pump system can be calibrated separately or synchronized with the calibration of the hydraulic wrench. Evenly select no less than 10 pressure calibration points within the output pressure range of the hydraulic pump, and connect the hydraulic pump and the pressure calibrator in series.

7. Gently pressurize, record the pressure value of the hydraulic pump and the indication value of the pressure calibrator, and measure each pressure calibration point at least 3 times.

8. Process data, calculate the non-linear error, repeatability and other technical indicators to ensure accurate and reliable data.

Notes on hydraulic torque wrench calibration

1. Put the hydraulic wrench and the torque sensor on the torque verification workbench, and connect the three with the connecting shaft and the adapter. During the connection process, be sure to make the workbench firm and stable, and keep the torque sensor and the hydraulic wrench torsion axis. Level and strictly require coaxial.

2. 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 relative to each other during the process of applying force to the hydraulic wrench.

3. 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.

4. Correctly install the hydraulic wrench on the standard device, and then apply it to the rated torque value step by step according to the selected verification point, and read and record the torque value of each point. This procedure is carried out at least three times.

5. After each application to the rated torque value, remove the load, check the zero position of the standard unit and hydraulic torque wrench indicator, and re-adjust the zero position.

6. When using the hydraulic wrench calibration device, first check whether the reaction arm of the hydraulic wrench calibration device is reliable, whether the hydraulic oil pipe is damaged, and whether the connecting workpiece is cracked.

7. The hydraulic wrench calibration device cannot be used to calibrate hydraulic wrenches with a rated torque value exceeding its maximum range.

8. During the operation, be sure to work in a safe area. If there is a special situation (abnormal noise, etc.), immediately reduce the pressure value until it stops working.


Hydraulic wrench calibration is not a very troublesome thing. As long as you have a professional torque calibration tool, you can calibrate the hydraulic wrench yourself according to the corresponding procedure. Therefore, if you frequently use a hydraulic wrench, it is recommended that you purchase a torque calibrator, which is much cheaper than entrusting a torque calibration service to an agency.