# Blog

## Can a Torque Multiplier Be Calibrated

As one of the commonly used bolting tools in industrial production, the torque multiplier has the advantages of simple, fast, and precise tightening of bolts. However, after long-term use, calibration is required to ensure the accuracy of its output torque. So, in this article, we will mainly discuss two questions, can the torque multiplier be calibrated? How to calibrate a torque multiplier?

## How a torque multiplier works

The torque multiplier uses the amplification effect of the gear train structure to amplify the input torque value at a certain rate to obtain a larger output torque value. It is an instrument used to tighten bolts and nuts connecting equipment components. It can apply a certain amount of torque on bolts and nuts to meet the pre-tightening force requirements.

The torque multiplier is suitable for situations where other torque wrenches are difficult to use. It can apply torque smoothly and protect the fastened equipment from greater external forces. Torque multipliers are widely used in aviation, aerospace, and shipbuilding industries.

## Can the torque multiplier be calibrated?

First, the torque multiplier can be calibrated. At the same time, it also needs to be calibrated after long-term use to ensure the accuracy of the output torque.

Nowadays, most users use the torque multiplier according to the nominal transmission ratio designed by the factory. They only use it as an assembly tool and do not manage it as a measuring instrument.

Moreover, different users have great differences in the use and calibration methods of the torque multiplier. It is difficult to ensure that the values provided by it are accurate and reliable, which seriously affects the assembly quality of the equipment.

Therefore, through the calibration practice of different torque multipliers, we have obtained the necessity of periodic calibration according to the correct calibration method.

## How do you calibrate a torque multiplier?

### Calibration device

The calibration uses the TSD-200000-TM torque multiplier calibration device platform. Choose from multiple torque sensors with different ranges to expand the device’s measurement capabilities.

The input torque measurement range of the calibration device is 20-2700Nm, the output torque measurement range is 200-27000Nm, and the system error is ±0.3%. The device can apply torque at a constant speed, and the computer automatically collects and processes data.

Use the above device to calibrate technical indicators such as torque multiplier indication repeatability, azimuth error, and transmission ratio error.

### Repeatability calibration

Select three test points within the measurement range of the torque multiplier, including the lower limit and upper limit of the measurement range.

Randomly select a position at the output end of the torque multiplier, apply torque to the torque multiplier, and based on the given torque value indicated by the measuring indicating instrument at the output end of the calibration device, read the indicated value of the measuring indicating instrument at the input end of the calibration device.

Measure point by point in the order of increasing torque value. After the output torque value of each stage of the torque multiplier is added, read the indicated value of the input end measurement indicator until the rated torque is reached, and then remove the torque. Measure 10 times in this direction continuously.

Calculate the value of R according to the formula.

In the formula:

Mi is the ith reading value of the input torque of the torque multiplier during repeated measurements.

Mmax is the maximum value of 10 readings of the input torque of the torque multiplier.

Mmin is the minimum value; it is the average of 10 readings.

R is the repeatability value.

### Azimuth error calibration

Select 7 test points within the measurement range of the torque multiplier, including the lower limit and upper limit of the measurement range, and each test point is roughly evenly distributed.

Apply torque to the torque multiplier, and based on the given torque value indicated by the measuring indicating instrument at the output end of the calibration device, read the indicated value of the measuring indicating instrument at the input end of the calibration device.

Conduct measurement tests point by point in the order of increasing torque values. After the output torque value of each stage of the torque multiplier is added, read the indicated value of the input end measurement indicator until the rated torque is reached, and then remove the torque.

Randomly select an orientation to perform a cycle measurement, which is defined as the 0° orientation of the torque multiplier.

Remove the torque multiplier, rotate the input end of the torque multiplier so that the output end rotates 90°, 180°, and 270° in azimuth, and perform a cycle measurement after each azimuth change.

Calculate the value of Ep according to the formula.

In the formula:

Ki is the measured transmission ratio in each direction of the torque multiplier.

Miout outputs torque values for each direction of the torque multiplier.

Miin enters torque values for each direction of the torque multiplier.

K0°, K90°, K180°, and K270° are the measured transmission ratios of the torque multiplier at 0°, 90°, 180°, and 270° orientations respectively.

K is the average transmission ratio in each direction.

Ep is the torque multiplier orientation error.

### Gear ratio error calibration

Calibration method Same as azimuth error calibration.

Calculate the value of e according to the formula.

In the formula:

e is the torque multiplier transmission ratio error.

Ks is the nominal value of the torque multiplier transmission ratio.

## In the end

The torque multiplier should be calibrated periodically according to the measuring tool to reduce quality and safety hazards caused by wear, fit accuracy, and changes in lubrication status during long-term use.

Calibration of the torque multiplier should be performed for azimuth error, repeatability, and transmission ratio error. When certain technical indicators have large errors, corresponding control measures should be taken.

Only by adopting correct calibration and usage methods can the assembly quality of the product be ensured and quality and safety hazards avoided.