Is it possible to calculate the life of a Centrifugal Pump? If pumps rotate in reverse direction twice or thrice a day how will the life be affected?

The life of the pump will depend on the medium and if there are solids or other harmful products. For example if the fluid is acidic or basic it could add additional wear and solids could cause wear on the interface between the walls of the pump and blades. There isn't a simple calculation that I am aware of for determining the life of a pump, there are many factors that would go into it. I would contact the manufacturer and ask if they have data on the average life of the pump for a similar fluid.

I think life of a centrifugal pump can not be calculated.It depends on so many factors like type and nature of materials used,maintainance of pump ect.Other thing if it will run in reverse direction more time life of the pump will be decrease.If any idea please write.

In addition to solids in solution and pH, air bubbles will also cause damage to the blades. Make sure the pump is protected agains runnning dry.

With proper maintenance and correct operation, pumps will last essentially, forever. You may need to replace seals, bearing and the motor eventually, but the casing, shaft and impeller should be good. Reverse running may damage the seals/bearings. I would ask why your pumps are operating in reverse? Is it because of reverse flow when the pump is stopped? If so, the normal practice of installing a check valve immediately downstream of the pump should prevent this.