Preparation For Extended Lay-Up - CleaverBrooks FLX Operation, Service And Parts Manual

Pressure Vessel Care
Waterside Inspection
Check all water piping and valves for leaks, wear, corrosion,
and other damage. Replace or repair the piping and valves as
necessary. Inspection covers at one end of the upper and
lower drums provide access to the interior of the drums for
visual inspection or washout. The interior surfaces of the
drums should be examined for any sign of corrosion or
accumulation of deposits.
J. PREPARATION FOR EXTENDED
LAYUP
Many boilers used for heating or seasonal loads or for
standby service may have extended periods of non-use. The
procedures outlined in this section are designed to allow a
boiler to be kept off line for any period of time without
damage to the unit. Special care must be taken so that neither
waterside nor fireside surfaces are allowed to deteriorate
from corrosion. Operating boilers can be protected from
corrosion and scale by applying various chemical treatments
and monitoring the system on a regular basis. However,
boilers that are taken off line, even for short intervals, are
susceptible to oxygen attack. Boiler drums and/or tubes may
sustain pitting type damage during either wet or dry layup if
proper precautions are not taken.
Oxygen solubility at ambient (off-line) temperatures can be
many times that of normal boiler operating temperatures. The
higher the oxygen concentration, the greater the oxygen
corrosion potential. Problems also can occur as a result of
improper shutdown procedures, where settled solids can dry
in a hard, adherent deposit.
Care must be take to prevent fireside corrosion, especially
when firing oil that contains sulfur. Dormant periods, and
even frequent shutdowns, expose the fireside surfaces to
condensation during cooling. Moisture and any sulfur residue
can form an acid solution. Under certain conditions, and
especially in areas with high humidity, the corrosive effect of
the acid can be serious. An acid solution could eat through or
severely damage boiler tubes or other metal heating surfaces
during the time that a boiler is out of service.
Too many conditions exist to lay down definite rules for
individual installations. In general, there are two methods of
storage: wet or dry. Your local Cleaver-Brooks authorized
representative can recommend the better method based on the
circumstances of your particular installation. Regardless of
the method employed, the boiler should be thoroughly
cleaned and inspected prior to storage. With either method,
common sense dictates a periodic recheck of fireside and
waterside conditions during layup to meet the requirements
of special or job site conditions.
750-177
Preparing The Boiler For Layup
To prepare a boiler for layup, thoroughly clean the fireside by
removing any soot or other products of combustion from the
tubes, exposed drum surfaces, and refractory.
! DANGER
The insulating refractory covering the top of
the bottom drum must be protected from
damage when work is being done in the
boiler furnace area. Damage to the insula-
tion may eventually cause damage to the
boiler itself.
Generally, a good brushing will clean fireside surfaces. Use a
wire brush for metal surfaces and a soft bristle brush for the
refractory. Sweep away or vacuum any accumulation.
To prevent condensation from forming in the control cabinet,
keep the control circuit energized. For extended layup
periods, especially where high humidity or large swings in
ambient temperature occur, the flame safeguard control
should be removed and stored in a dry atmosphere.
It is recommended that the burner air inlet be blocked to
prevent the flow of warm, moist air through the boiler.
! DANGER
A label should be affixed to the burner ad-
vising that the air inlet has been blocked.
Failure to remove the air inlet block when at-
tempting to operate the burner may result in
damage to the equipment.
Dry Storage
Dry storage generally is used for boilers that are to be out of
service for some time or for boilers that might be subjected to
freezing conditions. With the dry storage method, the boiler
must be thoroughly dried because any moisture would cause
corrosion. Drying can be accomplished by the use of a small
stove or heater.
Both fireside and waterside surfaces must be cleaned of all
scale, deposits, soot, and other combustion products as soon
as possible after shutdown.
All openings to the pressure vessel, such as handholes or
inspection ports, should be closed tightly. Feedwater and
system valves should be closed. Dampers should be closed to
prevent air from reaching the fireside surfaces.
Steps must be taken to eliminate moisture by placing
moisture-absorbing materials on trays inside the boiler. Two
moisture-absorbing materials are: quick-lime (at 2 pounds for
3 cubic feet of volume) or silica gel (at 5 pounds for 30 cubic
feet of volume). As soon as the material is in place, close all
boiler openings and blank all connections.
Chapter 3
CAUTION
CAUTION
3-9