Cleaning parts using spray
washers or immersion systems is sometimes prohibitive due to the
size of the parts. Ships, airplanes and rail cars are a few of the
items that require a different approach to surface preparation.
One
method of surface preparation is dry blasting of which there are
two common types: air blasting and airless turbine wheel type blasting
systems.
Air
blasting uses compressed air to propel media against the workpiece.
Centrifugal (wheel) types use centrifugal force to propel the media.
The two types of compressed air blasting systems are suction and
pressure blast processes.
Suction
type blasting systems use blast guns with two hoses. One hose handles
incoming compressed air and the other handles media. A vacuum is
created when the compressed air passes through the suction gun.
The vacuum pulls the media through a hose, and air and media are
propelled toward the workpiece. The vacuum created, the lift required
and the type of abrasive control the amount of abrasive.
Direct
pressure systems propel media using direct pressure from a pressurized
media storage bin. This creates a higher velocity. Direct pressure
units are used for processing large components, such as aircraft
and ships, since they can be used in either cabinets or portable
equipment.
In
an airless turbine wheel unit, a high-speed rotating paddle wheel
propels the media randomly toward the component. The blast stream
is larger because of this. It is used for light burr removal, cosmetic
finishing and surface preparation. Less abrasive and heavy media
must be used with these systems so that the media will reach the
workpiece.
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Portable
blasting is used for large items such as ships, aircraft and
rail cars.
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Alabama
Shipyard
Alabama Shipyard (Mobile, AL) was looking for a way to improve maintenance
and construction applications. Because complete hulls, sections
and components had to be blasted and protected for marine vessels,
the sheer size of the work was a challenge.
One
of its largest projects was a three-story BCPR blast room that doubled
as a paint facility. Because of EPA and OSHA concerns, as well as
the need for improved productivity, open blasting was replaced with
an enclosed blast cleaning process. The blasting room, supplied
by USF Surface Preparation Group, recovers spent media, using the
room's floor recovery system and Schmidt vacuums. Recovered steel
shot is placed back into a storage hopper. From there it goes to
a wash system and back into a double chamber blast pot.
After
blast cleaning, the plenum doors in the room are repositioned, converting
the room into a paint spray facility.
McEntire
Air National Guard Base
As one of only a handful of "stand alone" National Guard
bases in the country and the home of South Carolina Army and Air
National Guard, McEntire Air National Guard Base in Eastover, SC,
required numerous maintenance services.
McEntire
was looking for a number of maintenance and facility solutions,
including upgrading facilities and replacing equipment. After a
productivity audit that focused on the paint and blast facility,
engine and transmission rebuild bay, radiator cleaning and equipment
wash down bays, detailed surveys and equipment were evaluated for
solutions to maintenance productivity.
The
Base converted the blast room operation from garnet to aluminum
oxide, upgraded all ducting through the blast and paint facility
and replaced outdated equipment and hand tools with Graco applicators,
Dynabrade tools and Accustrip equipment.
The
Base also completed a major aircraft hangar floor restoration, replacing
an existing and ongoing sand blast operating that was contaminating
aircraft maintenance operations.
Ministry
of Railways of Russia
After more than a year of detailed analysis and study, the Ministry
of Railways of Russia (MPS) ordered three blasting systems for its
facility in Burlington, Ontario, Canada. The MPS employs 1.3 million
and has more than 140,000 kilometers of rail track. All Class One
railways of North America combined would equate to one third of
the rolling stock used by the entire railway system of Russia. The
Wheelabrator blast wheels throw steel abrasive using centrifugal
force.
This order
was the largest of its kind in the surface preparation blast industry
in Russia. The Russian market has much potential and the company
has made a long-term commitment to allocate resources and people
to continue to develop the trust and confidence of the Russian business
community.
