Several tube burst failures occurred on the similar position of a 300 MW unit boiler's final superheater.The burst tube panel is close to the bottom of the final superheater inlet header

right against the steam source of the second stage desuperheater.Such factors as broken of the water spray pipe for second stage desuperheater

improper operation of the second stage desuperheating water during the boiler's start and running were considered as the main reasons that easily resulted in accumulation of desuperheating water which was not well atomized in angle heads of the heating tubes

leading to water blocking caused tube burst.Thus

to prevent the water blocking in heating surface

several countermeasures were put forward

like ensuring the furnace is heated evenly during the boiler start

controling the desuperheating water flow in initial stage strictly

using the second stage desuperheating water as less as possible

and so on.