Boiler protection during shut-down

[wayuu1981]

We are going to cut a boiler wall section to change the reheater tubes trough this opening, the opening will be 5 meters long and 0.7 meters width (it will cut six water wall tubes).

My question is: if the boiler shut-down will last 32 days, approximately the boiler wall will be cutted for about 30 days. Before the cutting, the boiler was cooled and drained, but the superheaters had protection water that couldn't be drained. (we usually use the wet method, but, due to the wall cutting, is not possible this time).

what is the best way to protect the boiler during shut down? to drain the boiler as much as we could? or trying the installation of plugs on tubes openings to perform our usual wet protection? or is there a better way.

Javier Guevara E.
Projects, Mechanical Engineer
TERMOGUAJIRA - GECELCA S.A. E.S.P.

 

[eyec]

don't know if you want to go this far, but you could freeze above and below the cutout section, install temp pulgs and keep the wet layup.

Steven C
Senior Member
ThirdPartyInspections.com

 

[metengr]

Completely drain the boiler (hot flash drain to remove condensate) if open to atmosphere for this period and dehumidify with actual dehumidifiers, if necessary. You need to protect the magnetite layer on the CS waterside tube circuit.

 

[wayuu1981]

The tubes we cut, are close to the upper waterwall header, so we filled the boiler to the lower cut level and we welded the plugs on the lower and upper cuts, then we completely filled the boiler.

About metengr's answer, we don't have dehumidifier in our boiler, and, as we began the boiler shut-off almost a week after the boiler was cooled, filled full and protected with the wet method, we drained the boiler by the lower headers at ambient temperature (80 F) but the superheaters couldn't be drained because its geometry. About protecting the magnetite layer, is it done chemically whit boiler drained? or you mean to avoid mechanical impacts?

Javier Guevara E.
Projects, Mechanical Engineer
TERMOGUAJIRA - GECELCA S.A. E.S.P.