How will electromotor intended for 460V be affected by working on an installation on 440V?
the standard NEMA design specifications for ac INDUCTION motors are that they will deliver rated HP at +-10% of rated voltage. 

Peak torque capability of the motor will decrease at the square of the voltage difference. So 440/460 = 95.7% (well within the 10% tolerance), squared means the peak torque will drop to about 91% of normal. Motors only come in certain sizes, so at some point someone picked that 150HP motor for a specific amount of torque that it produced at rated speed, because the next size down, 125HP, was not going to provide enough torque. In the vast majority of cases, the amount you need is less than the amount the motor is capable of, so the chances that the original design engineer picked a motor that was less than 9% larger than necessary is very slim. I would not hesitate to use it.