Abstract: The structure characteristics and working principle of the dividing combining  valve were introduced, and the reasons for the short service life of the dividingcombining valve in the pressure plate lifting hydraulic circuit of MIEBACH laser welding machine of the APL normal pickling unit were analyzed in detail. The analysis results showed that the rated flow of the original design of the dividingcombining valve could not meet the actual flow on site, and the valve core had a large impact when it worked, and the frequent action impact caused the valve core to be broken and damaged. The problem could not be solved by adjusting other hydraulic valves in the hydraulic circuit,so the dividing combining valve was upgraded according to the actual flow and working pressure, which not only ensured the normal lifting action of the welding press plate, but also completely solved the problem of short service life of the dividingcombining valve.

Key words: dividing combining , valve, MIEBACH laser welding machine, hydraulic circuit