1. minor repairs
It means the minor maintenance activities for the on-site pipelines. 
It contains the maintenance activities such as changing the packing, replacing accessories joints and pipes, filling grease to lubrication position, replacing diaphragm online, spring and seals and so on.
2. medium repair
It means to remove and install actuator and valve end cover, ,and change the packing and valve sealing gasket ,and remove and install the valve rod, valve spool, valve seat and valve cage and so on, and do effective grinding and assembling works.
3.over haul
It means the processing of removing the flange bolt of the regulating valve, and completely stopping work to be disintegrated to do the comprehensive maintenance, debugging, and pressure test.