10 percent of Lower Explosive Limit (LEL). System may incorporate any
combination of solid desiccant and direct expansion refrigeration
equipment. No liquid, granular, calcium chloride, or lithium chloride
drying systems will be accepted. Use only electric, indirect fired
combustion, indirect friction, or steam coil auxiliary heaters. System
shall be compatible with removal of dust and solvent vapors, and shall have
fail-safe measures to ensure reliability during operations.
3.6.1.1
Humidity Control for Surface Preparation and Primer Application
Provide and utilize dehumidification equipment to maintain relative
humidity at appropriate level to prevent prepared steel surfaces from
corroding at all times during abrasive blasting through primer application.
Failure of humidity control system, or failure to maintain proper
conditions, during surface preparation stage may allow surface rusting,
which will be rejected and require rework. All surfaces to be coated must
meet all requirements of SSPC SP 5 at time of primer application. Failure
of humidity control system during primer application stage will be cause
for removal and replacement of all materials applied and cured while
conditions were not as prescribed above.
3.6.1.2
Humidity Control for Application of Intermediate and Topcoats and
Initial Curing
Provide and utilize dehumidification equipment to maintain relative
humidity near the coldest steel surface in tank below 55 percent at all
times during coating application, and during the first four days of initial
curing after application of topcoat. This measurement is not the same as
measuring the relative humidity of ambient air in the tank, and will
require either electronic equipment to monitor relative humidity at the
steel surface, or complex calculations to convert relative humidity of air
in tank to relative humidity at steel surface. An approved alternative
method of monitoring dehumidification that requires less sophisticated
equipment or calculations is to maintain a minimum dew point depression of
10 degrees C 18 degrees F below coldest steel surface temperature. This is
in lieu of specific relative humidity and dew point requirements in this
Section. Failure to maintain specified humidity control during this phase
will be cause for extension of humidity controlled cure time to ensure four
consecutive days at specified relative humidity at steel surfaces.
Formation of condensation in coating application stage prior to the
indicated dry-hard time will be cause for removal and replacement of all
materials contacted by condensation.
3.7
EQUIPMENT USED IN TANK
Equipment used in the tank after surface preparation begins shall not leave
any oily residue from exhaust or other sources. Internal combustion driven
equipment, other than that powered by natural or bottled gas, shall not be
used.
3.8
SURFACES TO BE COATED
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NOTE: See MIL-HDBK 1022 for guidance on which
interior tank surfaces should be coated.
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Prepare and coat interior tank surfaces, including[ FLOOR][, SHELL][,
CEILING][spot repair of [____] spots of [_____] square meters square feet].
SECTION 09970
Page 22
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