The causes leading to overtemperature of return oil from hydraulic coupling of I.D.fans in the debugging process of CFB boilers for 4×200 MW units have been analysed.It is believed that the main causes resulting in overtemperature of return oil from hydraulic coupling of I.D.fans are unproper installation of mechanical parts at inlet of I.D.fans and impefect regulating mode of said fans

making load and shaft power of them to be increased.The scheme of solution has been put forward as follows:(1)adjusting the rotating direction of baffle plates at the force-bearing end of I.D.fans

and adjusting the open degree of baffle plates at inlet of said fans;(2)on the basis of existing oil system of hydraulic coupling

additionally installng auxiliary oil pump;(3)improving the debugging mode in start-up of the I.D.fans.After implementation of above-mentioned scheme

the overtemperature problem of return oil from the hydraulic coupling has been solved.