With the common application of DCS in large thermal power plants, how to determine the content of DCS overhaul, overhaul cycle and maintenance projects to ensure the safe operation of DCS in thermal power plant application conditions, is the key to improve its reliability. In practice, full use should be made of the computer system self-diagnostic function, early detection of abnormalities, to prevent module failure; overhaul should also have a reasonable overhaul process and procedures, taking into account the DCS itself overhaul and attention to the control system external equipment overhaul, and to list the overhaul considerations according to the characteristics of the DCS system, to do a certain amount of protective measures to avoid damage to the DCS device modules in the overhaul. DCS major and minor repair projects According to the characteristics of computer control equipment, DCS, in addition to peripheral equipment maintenance like conventional control equipment, at least the following items should be overhauled with the major and minor repair of the unit, i.e., module configuration copy, verification of control module markings and addresses; cleaning power supply, modules and dust filters, inspection and tightening of control cabinet wiring, grounding system inspection, cooling fan overhaul, power supply equipment overhaul test; important measurement and protection Signal line insulation check; electronic room temperature, humidity and dust content test before overhaul, review after overhaul; module power supply and redundant module switching test; alarm and protection function test; communication, manual operation station check; carry out card for calibration, etc.; overhaul before making adequate preparations, overhaul to strictly implement the process card system, and carefully do the overhaul records, power supply, module and other tests to fill in carefully Test report. (1) Overhaul project The overhaul of DCS system is carried out with the overhaul of the main equipment of the unit, and the overhaul project includes the following contents. 1) Check the control equipment thoroughly and make records. 2) Copy the configuration of all modules and verify the module flags and addresses. 3) Clean the control cabinet power supply and modules, clean the dust filter of the panel cabinet. 4) Check and tighten the control cabinet wiring and fixing screws. 5) Check grounding system, power supply performance test, line insulation test. 6) Dustproof and seal the control cabinet and replace the cooling fan. 7) Overhaul the recorder, printer, alarm window, human-machine interface equipment, etc. 8) Eliminate defects that cannot be handled during operation, restore and improve various signs. 9) Hardware equipment function test, configuration software loading and inspection. 10) Measurement module calibration, on-site equipment overhaul. 11) Protection interlock test. 12) Inspection and replacement of cables, pipelines and their accessories. (2) M...