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 cleaning, solvent cleaning should be repeated. Painting must be started and completed as soon as
possible after power cleaning.
b. Types of Power Tools. Chipping hammers are used to remove tight rust, mill scale, and old paint
from large metallic and masonry areas. Wire brushes (cup or radial) are used to remove loose mill scale,
old paint, weld flux, slag, and dirt deposits. Grinders and sanders are used to smooth excessively rough
surfaces. As with hand tools, care must be exercised with power impact and grinding tools so they do not
cut too deeply into the surface, resulting in burrs that are difficult to cover and protect satisfactorily. Care
must be taken when using wire brushes to avoid polishing metal surfaces, which would prevent adequate
adhesion of subsequent coatings.
protection against flying particles should be worn. In addition, gloves, aprons, and leggings may be
advisable if there is a problem with hot sparks. Respiratory protection filter masks should be provided for
prolonged exposure. These tools should not be used near readily ignitable materials or within 50 feet of
volatile flammable liquids, such as those used in cleaning and painting. In addition, operations should not
be conducted where there is the possibility of the presence of combustible gases.
3-12. Abrasive Blasting. Abrasive blasting is the preferred method for preparing metal surfaces. Blast
cleaning abrades and cleans through high-velocity impact on the surface with sand, metal shot, metal and
synthetic grit, or other abrasive particles. The abrasive is discharged, either wet or dry, under pressure.
The wet system differs from the dry in that a solution of water and rust inhibitor is incorporated with the
blast abrasive. The rust-inhibiting solution either is mixed with the abrasive in the pressure tank or is
introduced into the blast stream just behind, or just in front, of the blast nozzle. All blasted metal surfaces
require that prime painting be started and completed the same day to prevent new rust from forming.
Blast-cleaned surfaces are subject to rapid rusting if not coated.
requirements that shall be taken to prevent introduction of abrasive-blasting materials into ship spaces
and unprotected equipment, and to prevent injury and property damage, are described in paragraph 2-18.
These precautions apply to all abrasive blasting operations on and within the vicinity of US Army
Watercraft.
a. Preoperational Requirements. Abrasive blasting shall not be undertaken until positive steps have
been taken to prevent contamination and spread of abrasives and dust to adjacent compartments,
machinery, and equipment. Abrasives and dust can enter ships through open sea valves, hatches,
Ventilation systems, temporary openings, normal entryways, which are frequently opened and closed,
and entryways, which must remain open to accommodate other work. If there is any possibility that
abrasives can enter a ship or ship's compartment in spite of all possible precautions, critical machinery
surfaces and parts, and electric and electronic equipment, shall be positively sealed or otherwise
various stages of disassembly are especially subject to damage from contamination.
(1) Prior to blasting operations, the responsible shop shall notify all other ships in the vicinity, of time
and location of proposed abrasive blasting operations. All shops and the ships force shall take the
following precautions to protect equipment and structures:
(a) Drop cloths and masking shall be used to prevent damage from the abrasive material.
(b) Temporary shields and other sealing or closing-off measures shall be used to prevent abrasives
from entering machinery, pipes, seawater inlets, and pump wells through various openings.
(c) Where remote service connections provide water or ventilation, such as seawater from the
auxiliary seawater system while the ship is in dry-dock, the inlet to that connection shall be positioned and
measures taken to prevent the entry of blasting contaminations.
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