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Form 2055
20
Revision Date 5/1/2015
Drain the boiler before the steam pressure falls to zero. Then pressurize with 5 psig nitrogen gas
through a suitable top opening during draining. The nitrogen pressure is to be maintained through
draining and subsequent storage.
An alternate method is to completely dry a clean boiler (by blowing hot dry air through the boiler)
and then purge the air from the boiler and pressurized with 5 psig nitrogen. Be aware that all
metal surfaces that are not completely dry are vulnerable to corrosion, particularly if oxygen is
present.
If a boiler has been down for repairs and is to be laid up, it should be operated to pressurize with
steam and then drained and pressurized with nitrogen as in Step 1.
All connections must be blanked or tightly closed.
NOTE:
Operating boilers must be removed from service to minimize adherence of boiler water
suspended solids on boiler metal surfaces. Refer to previous instructions for boiler washdown.
3 . 9 . 1 0 R E T U R N I N G I D L E B O I L E R T O S E R V I C E
After wet lay-up
To start an idle boiler after wet lay-up, use the following procedure:
If the boiler was pressurized with nitrogen, disconnect the nitrogen supply source and
vent the boiler.
Using the blowdown valve, drain the boiler partially and make up with feedwater so as
to dilute the chemical residuals to operating concentration levels.
After the boiler water concentrations and the water level are returned to proper
operating conditions, the boiler can be started in the normal manner.
After dry lay-up
To start an idle boiler after dry lay-up, use the following procedure:
Disconnect the nitrogen supply source and vent the boiler in a safe manner – external
to the building and away from air intakes. Then thoroughly purge the boiler of nitrogen
with dry air.
The boiler was to have been cleaned before the lay-up procedure. So it is necessary
only to fill the boiler with properly treated water. Then proceed with start-up.