A new type of Large Cover for Preventing the Tension in the Cooling Process of the External Pressure Pipe of the DC Boiler

The all through-wall tubes of the top of sealed big cover in the supercritical once-through boiler have actively implemented when the one-through boiler is stop and cooled. Firstly, the verti- cal water wall of upper furnace and external furnace. Secondly, the platen superheater and high temperature superheater of the upper furnace and their upper through-wall tube. Finally, as the up- per through-wall tube and every header contract and tear, we need to install vent and axial flow fan, which can lower temperature and monitor the contracting of the extemal through-wall tube of fur- nace, and have the ventilate function in the confined space for the top of the sealed big cover.