METHOD AND DEVICE FOR CALIBRATION OF A PRESSURE AIR SUPPLY SYSTEM FOR A PNEUMATIC POWER WRENCH INCLUDING A REMOTELY LOCATED PRESSURE CONTROL UNIT

摘要

A method and a device for calibrating a pressure air supply system for a pneumatic power wrench (10) including a remotely located pressure air control unit (11), and a pressure air supply conduit (14) connecting the power wrench (10) to the pressure air control unit (11), wherein the pressure air control unit (11) controls the operation of the power wrench (10) by changing in a shifting point (ts) the pressure of the air supplied to the power wrench (10) from one level to another so as to accomplish stop of power wrench operation, wherein a time delay (?t) is caused by the pressure change propagation time through the pressure air conduit. The air conduit related time delay (?t) is calculated in response to the pulse length (t2-t1) of relay controlled successive pressure pulses induced in the pressure air conduit (14), and an advanced pressure change point (tAS) is determined from the calculated time delay (?t).