MIL-HDBK-1110
described in SSPC SP 11. Care must be taken when using wire
brushes to avoid burnishing the surface and thus causing a
reduced adhesion level of the primer coating. Grease and oil
must be removed prior to power tool cleaning. Danger from sparks
and flying particles must always be anticipated. The operator
and adjacent workers must wear goggles or helmets and wear
protective clothing. No flammable solvents should be used or
stored in the area. Refer to Section 13 for further safety
details.
6.7.9
Steam Cleaning. A high-pressure jet of steam (about
300 degrees F, 150 psi), usually with an added alkaline cleaning
compound, will remove grease, oil, and heavy dirt from surfaces
by a combination of detergent action, water, heat and impact
(refer to SSPC SP 1). The steam is directed through a cleaning
gun against the surface to be cleaned. The pressure is adjusted
to minimize spraying time. Any alkaline residue remaining on the
surface after the cleaning operation must be removed by thorough
rinsing with fresh water. Alkali cleaners used in steam cleaning
may attack aluminum and zinc alloys and should not be used on
these substrates. Steam cleaning may cause old paints to swell
and blister. Thus, when steam cleaning previously painted
surfaces, the cleaning procedure should first be tested in a
small area to assess the effect on the old paint.
Steam cleaning equipment is usually portable and is one
of two designs. With one type of equipment, concentrated
cleaning solution is mixed with water, fed through a heating unit
so that it is partially vaporized, pressurized, and forced
through a nozzle. With another type of equipment, sometimes
called a hydro-steam unit, steam from an external source is mixed
with the cleaning solution in the equipment or in the nozzle of
the cleaning gun. The shape of the nozzle is chosen according to
the contour of the surface being cleaned. Steam cleaning is
dangerous and extreme caution should be exercised with the
equipment. A dead man valve must be included in the equipment
and the operator must have sound, safe footing. Workers engaged
in steam cleaning operations must be protected from possible
burns and chemical injury to the eyes and skin by protective
clothing, face shields, and the like. Refer to Section 13 for
safety details.
6.7.10
Water Blast Cleaning. Water blast cleaning uses a
high-pressure water stream to remove lightly adhering surface
contaminants. Selection of water pressure and temperature and
addition of a detergent depend on the type of cleaning desired.
Low pressure - up to 2000 psi - (sometimes called "power
washing") is effective in removing dirt, mildew, loose paint, and
chalk from surfaces. It is commonly used on metal substrates and
generally does little or no damage to wood, masonry, or concrete
97
Previous Page
