The repair of ventilator axle journal with serious wear was achieved by using the method of laser cladding.

There was big vibration in blower bush (linking up with a speed increasing box) vertically and axially after changing of the speed increasing box gears of the blower.

The character on change of the shaft power with the differential pressure or rotational speed for Roots blower is analysed, the conversion formulas for the shaft power are deduced.