Knowledge sharing on “All about Centrifugal Pumps” for Engineering students/young Engineers/professionals of oil & gas industry. Series -6

Know about balancing disk and its function how does it balances the axial hydraulic thrust in multistage centrifugal pumps.?

The rotating part of an axial-clearance hydraulic balancing device (Fig-1) is a balancing disk and the stationery part is known as balancing disk head.

The balancing disk is fixed to and rotates with the shaft, being separated from the balancing disk head by small amount of axial clearance. Leakage through this clearance flows in to the balancing chamber and to the pump suction or suction source.

Balancing chamber pressure exists on the back of the balancing disk, while its face is subjected to an intermediate pressure between discharge pressure at the smallest diameter of the disk and the balancing - chamber pressure at its periphery. Inner and outer disk diameters are so designed that the difference between the force acting on the face of the disk and that on its back balances the axial thrust of the impellers.

If the axial thrust of the pump increases, the excess pressure moves the rotor to reduce the clearance between the balancing disk and disk head. This reduces the flow through the clearance and lowers the balancing chamber pressure until the pump axial thrust is again balanced. Similarly, a reduction in axial thrust causes an increase in clearance between the disk and the disk head. As a result of increased flow, pressure increases in balancing-chamber until the axial hydraulic thrust is again balanced.

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                                 Fig-1.Balancing disk and balancing chamber arrangement