Revalidation is required when the equipment is modified,relocated,or otherwise changed in a manner which may effect the process.Any change in the equipment need to be evaluated to determine the potential consequences on validation status.The Revalidation may be required based on observed performance of equipment eastablished initial validation ,as long as routine process operate in a state of control and no changes have been made to process,equipment may not have to be revalidated.Depending on their usage equipment have to be calibrate on a monthly,quarterly.or semiannually basis.calibration ensures that equipment can be used safely and reliably.