What are preventive maintenance, improved maintenance and post-event maintenance?

Preventive maintenance is a maintenance activity carried out according to the pre-specified plan and corresponding technical requirements in order to prevent the performance and accuracy of equipment from deteriorating or decreasing.

Improved maintenance is an effective measure to eliminate the congenital defects or frequent failures of equipment, improve the local structure of equipment or equipment parts, and modify them in combination with repair to improve their reliability and maintainability. It is also an important part of preventive maintenance.

After-the-fact maintenance is also called fault maintenance, that is, unplanned maintenance when the equipment fails or the performance and accuracy drop below the qualified level.