Bearing Life Time

Condensate pump is using vertical pump to get sufficient of NPSH. The construction has many of bearings. The motor has installed at upper, lower and lower thrust.
The pump has installed upper, intermediete and lower bearing. For detail picture we can see on Gould Pump.

The axial thrust acting in the impeller can reduced by balancing holes in the impeller, and the residual axial thrust on the rotor weight are supported by motor thrust bearing.

In this casa we want calculated the motor bearing life time as the datas we have the pump's job deliver 1700 T/h hot well water to de-aerator / feedwater tank. The pump load is 1.22MW. So the calculated of motor torque describe as below.

From the calculation we know tho motor torque is 12 N.m.

The motor bearing from torque load can be determine the size. The design result thrust bearing use water close cooling and lowering bearing use grease for cooler.

So in our case the motor lowering bearing got high temperature then broken. The effect of high temperature make motor burn as well. The location of bearing you can see picture beside.










Please visit http://mechanic-info.blogspot.com/2012/09/antifriction-bearing.html
for bearing theory life time.

From calculated, the motor handle 12kN torque and can be assumed radial forced is 6kN due to it has lower and upper bearing (axial thrust neglected).

(i.Fa/Co) = (1.6kN / 13.4 ) = 0.44
i is number of row for ball bearing.

e = 0.52
Co and e from table.

Fa/Fr < e so that X=1 and Y=0 P = X.V.Fr + Y. Fa V = 1 for inner ring rotation. P = 1 x 1 x 6 kN = 6 kN L10 = (C/P)^b b is 3 for ball bearing and C from table. L10 = (26/6)^3 = 81.3 million revolution. L10 = (81.3 x 10^6)/983RPM x 60 L10 = 1378h = 57 days