Mass balancing means the balance of mass of turbine blades around the both sides of turbine shaft axis. Every object has a point called center of gravity through which the mass of that object acts. If this point of a turbine blade does not lie upon the center axis of shaft, an unbalanced condition will create which may cause the failure of turbine shaft as well as turbine. So it is very necessary to operate turbines with proper balancing.
In case of single blade when its center of gravity does not lie upon the center axis of shaft, an unbalanced condition creates due to the variation of mass center and center axis. For balancing, either welding or grinding is done on turbine blades. In which side the mass is less, welding is done there to increase mass in that side. Similarly in which side the mass is more, grinding is done to reduce mass from that side.
In case of multi-blade, it is very difficult to balance the mass center line through over the center axis line of the shaft. Hence dynamic balancing is needed.
Figure: Dynamic balancing of turbine blades.
It is nothing but a circular plate having some holes. In which side, the mass of the blades is lower, bolts are connected through the holes to increase mass in that side for balancing. Thus balancing is taken for smooth operation of turbines.