I'm in the process of designing the v-belt & pulley drive system for a cement factory fan. The fan itself weights about 60 Kg and has a diameter of 900 mm. It is to be run at 1440 rpm and the motor has power rating of 30 KW. It would operate 24/7.....a service factor of 1.4..How many belts should be used? Which size would be the best? C or D? Thanks for all your help!