API Spec 7, torque hammer weight tolerance

Hi,

I would not look for a written tolerance, but decide one from the specs of your torque hammer. I have not calibrated one before but the read-out of the torque hammer will be as accurate as the calibration performed.

Ie: if your hammer reading is to 1 decimal, then the calibration needs to compliment that, say 2 decimal places otherwise you will carry the error of the weight through out the hammers reading.

Further more, the calibration does not need to have the exactly the same weight every time. As long as the measurement of the mass is always accurate and the hammer is set to the calculated torque (from the measured mass).

For example if the weight over the years has changed, metal loss, or simply changed the mass, it will be sufficient to simply re-measure the weight of the mass each time as long as a new calculation of the torque is performed.

Personaly, I would measure the weight to 3-4 decimals everytime a calabration is done and re-calculate the torque required and use that.

Hope this helps.