The structural features of water-wall in boilers for ultra-supercritical 1000 MW unit in Yuhuan Power Plant have been presented

the phenomenon of over-temperature and tube-burst resulted from blockage of Fe3O4 scaling on the throttle plate of water-wall being analysed.It is believed that the cause leading to accident is the average value variation of iron content in the thermodynamic system

and preventive measures being put forward as in the following:(1)before putting unit into operation

chemical cleaning should be carried out;(2)the feed-water has to adopt oxygen treatment mode;(3)after operation of the unit

chemical cleaning has to be carried out.In addition

through strengthening iron ion supervision in operation

adopting water discharge under pressrue during shutdown of the boiler

and suitable blow-down during strart-up

as well as additionally installing temperature-measuring points on left and right wall of the boiler etc.

tube-burst in the boiler has been decreased

enhancing safety and reliability of the unit.