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FREQUENTLY
ASKED QUESTIONS ABOUT MBA CABINETS
Q: Why
are most MBA blast cabinets built standard with only
one door? [ ^ BACK TO QUESTIONS ]
A: There
are three very good reasons. Repeated observations over
the last thirty years show that nearly all blast cabinet
operators use the right side door only for loading and
unloading. The exceptions are usually operations that
require a pass through system to another workstation.
The second reason stems from the general physical characteristics
of people. About 90% of the world’s population
is right handed. Therefore, it is safe to assume that
about 90% of blast cabinet operators are right handed,
too. Right-handed blast operators typically blast with
the nozzle angled (more or less) towards the left. If
there is a door on the left side of the cabinet, extreme
stress is placed on the door seals. In a relatively
short period of time, the door seal will fail. Abrasive
and dust will escape from the cabinet through the failed
door seal. This problem is usually alleviated by frequent
replacement of the door seal, duct taping the door to
prevent dust and abrasive release or welding the door
closed (because it is never used anyway). Finally, one
well built double skinned, no spill door is better than
two single skin, poorly constructed doors.
--
Q: Why doesn’t
MBA use a freestanding dust collector like the other
manufacturers? [ ^ BACK TO QUESTIONS
]
A: Freestanding
dust collectors add additional floor space to the blast
cabinet. Extra floor space is usually non-existent in
most facilities. Detached dust collectors require duct
from the cabinet to the dust collector housing. This
duct increases the static pressure on the blower resulting
in lower dust removal efficiencies. It also means additional
wear parts to be purchased from the manufacturer. In
addition, the regulations for freestanding dust collectors
fall into a gray area for permits. Dust collectors not
bolted directly to the blast cabinet may require a permit
from the local air quality control agency or municipality.
--
Q:
Why does MBA use cartridge filters instead of envelope
or tube style filters? [ ^ BACK TO QUESTIONS
]
A: MBA
can manufacture dust collectors with every type of filtration,
but it is rare when a cabinet is sold without cartridge
filter dust collection. Dust collector filter area is
one of the most important factors when choosing a blast
cabinet. Dust collectors with greater filter area can
operate longer without service. It is technically feasible,
but not practical, to build different collectors of
the same filter area. Envelope filters yield about three
times the filter area per square foot of floor space
than tubular collectors. Cartridge collectors yield
double the filter area over envelope filters (six times
the area over tubular filters).
Dust collectors with greater
filter area are able to disperse the volume of air traveling
through the collector more efficiently. The efficiency
is commonly measured by the air to cloth ratio (the
ratio of exhaust blower volume to filter area). Ideally,
the air to cloth ratio in a dust collector should be
3:1 or less. Practically, air to cloth ratios between
3:1 and 5:1 are considered acceptable. Air to cloth
ratios above 5:1 exhibit significantly reduced visibility
in the blast cabinet and will lead to premature failure
of the filters which results in dust blowing into the
work area. Lower air to cloth ratios mean the dust collector
is more efficient and the filters will not wear out
as quickly (Please refer to Dust Collector Comparison
Chart).
Cartridge filters are very easy to replace. MBA cartridge filters can
be replaced in 10 minutes or less. Popular tube style
filter replacement can take up to three hours or more.
In addition, cartridge filter replacement is much less
expensive than tube style filter replacement. The construction
of the cartridge also facilitates easy adaptation to
automatic filter cleaning cycles. In short, cartridge
filters produce more filter surface, result in more
efficient dust collectors, take up less space, are easier
to rebuild and cost less to maintain than other types
of dust collection.
--
Q: Why doesn’t
MBA use a pulse jet cleaning system on all cartridge
dust collectors? [ ^ BACK TO QUESTIONS
]
A: MBA
uses a special cartridge filter that allows vibration
to effectively clean the filter. Vibration of the cartridge
filter effectively creates a dry, ultrasonic cleaning
action. If the filter is cleaned regularly, the filter
vibrator will remove up to 80% of the dust lodged on
the filter. The standard system on all blast cabinets
is manual pneumatic; the operator opens a valve and
allows the filter vibrator to clean the filter for 2-3
minutes before closing the valve. MBA also offers an
automatic version that automatically cleans the filters
for 2-3 minutes every time the machine is shut off.
MBA offers
automatic reverse pulse filter on two+ cartridge dust
collectors; the individual filters are cleaned every
fifteen seconds. MBA recommends purchasing the reverse
pulse for applications that are high production (4+
hours per day) and/or regions of the country that experience
high humidity.
--
Q:
Why doesn’t MBA use a 1 horsepower motor on their
dust collectors like the other manufacturers?
[ ^ BACK TO QUESTIONS ]
A: Unlike
many other manufacturers who use an off the shelf blower
assembly which must operate alone, MBA designs and builds
its own exhaust blowers. This allows MBA to consider
the motor horsepower taking into account the total machine
running or operating static pressure. Static pressure,
or resistance of the air to flow, prevents some air
from getting to the blower during operation.
Since MBA’s blowers are not off the shelf blowers
this allows MBA to use smaller motors. If the blower
were operating on a bench with no static resistance
from the machine the motor would need to be larger.
Therefore, fractional sized motors can be used which
creates an additional benefit of not having to hardwire
most MBA cabinets. If you require single power source electrical or larger exhaust blowers, MBA offers as
an option.
--
Q: Why doesn’t
MBA recommend using abrasive sized larger than 180 mesh
in their cyclone reclaim separators when the other manufacturers
encourage it? [ ^ BACK TO QUESTIONS
]
A:
It is important to realize that most of the other manufacturers
do not use a true cyclone reclaim separator. They usually
use a barrel separator (but commonly misrepresented
as a cyclone) that is less expensive to build and is
not nearly as efficient (some of the efficiencies are
as low as 70%). Some manufacturers only install barrel
reclaim systems on their production blast cabinets.
This results in the unnecessary replacement of many
high wear items when abrasive 150 mesh or larger is
used in the cabinet. These same manufacturers offer
a wear plate for the barrel separator as an option.
An uninformed customer will oftentimes not purchase
this option and needlessly replace the separator in
a short period of time.
MBA makes a variety
of abrasive reclaim separators. Abrasive larger than
150 mesh does not require cyclone reclaim separators
for retention or proper abrasive flow inside the cabinet.
MBA builds an abrasive reclaim separator that is 99%
efficient on particles 150 mesh or coarser and doesn’t
require 100% of the abrasive exiting the nozzle to flow
through the reclaim separator. This is accomplished
by storing the abrasive inside the blast cabinet not
outside the cabinet. This type of system eliminates
the high wear items of the cyclone separator system.
MBA builds a cyclone
reclaim separator for ultra fine abrasives (150 mesh
and smaller). Our cyclone has the highest efficiency
in the industry. It is 99% efficient for abrasives sized
from 150 mesh to 400 mesh. The frictional wear of ultra-fine
abrasives is significantly less than larger abrasives
so replacement of wear items is virtually non-existent.
The cyclone separator is also used to dry and make the
fine abrasive flow. MBA’s high-efficiency cyclone
is 80% efficient on abrasive 1-5 micron in particle
size.
MBA also builds
a barrel separator that is used in applications that
require a larger abrasive to be conveyed outside the
blast cabinet for recycling. This condition can exist
when the cabinet blast chamber is large. Using the barrel
separator with the larger abrasive produces a more serviceable
pneumatic abrasive conveyor.
--
Q: Why does MBA brace
the cabinet legs? If the legs are going to be braced,
why not use full sheets of steel?
[ ^ BACK TO QUESTIONS ]
A: Cabinet
leg braces insure that the machine will ship across
the country without damage or be moved within a facility
without damage. In addition, the leg braces can be used
to move the machine by forklift when received. Using
solid steel side legs blocks two sides of the cabinet
that can be used as access when servicing the machine.
One manufacturer even blends the solid steel sheets
into the front of the machine. This is oftentimes ergonomically
incorrect. Many machine operators have a difficult time
getting comfortable because there is no place for the
leg to bend when depressing the foot operated blast
valve. Most of the important service and adjustment
features of a blast machine are located at the bottom
of the machine hopper, so having access from more than
the back and/or the front of the machine is helpful.
In addition, all MBA cabinet hoppers are replaceable,
so standard braced legs lowers the shipping weight and
replacement cost.
--
Q: Why does
MBA offer cabinets with different window slopes? [ ^
BACK TO QUESTIONS ]
A: Customer
needs are not always the same. Parts for blasting may
be low profile (below 6” in height), or high profile
(above 12” in height). Parts are normally blasted
while setting on the metal work surface. The 45º-window
slope gives the operator the greatest visibility while
blasting low profile parts. High profile parts will
bring the part much closer to the 45º-sloped window.
This will create high window wear due to abrasive bounce
back. For this reason, MBA offers the 17º-window
slope in an expanded height cabinet. This allows additional
inside cabinet height and greater distance from the
part to the window, thus reducing window wear. However,
some visibility may be lost on low profile parts sitting
on the work grate inside an expanded height cabinet.
For this reason, we counsel customers to purchase the
cabinet that will work best for the greatest number
of parts.
--
Q: Why does MBA
use glass window protectors instead of the plastic window
protectors in their cabinets?
[ ^ BACK TO QUESTIONS ]
A: Plastic
window protectors are not desirable because of the soft
nature of the plastic and the high susceptibility of
the abrasive dust electrostatically sticking to the
window protector. Cleaning a window protector is typically
accomplished by wiping it with the operator glove. Unlike
glass, the plastic window protectors will easily scratch.
The result is poor operator visibility. Some manufacturers
use mesh screens as window protectors, but mesh screens
greatly reduce light and operator visibility and really
doesn’t completely protect the machine view window
from damage. Using glass as a window protector insures
maximum visibility with no light loss inside the cabinet
and does an excellent job protecting the view window.
--
Q: When a customer
wants additional cabinet protection, why does MBA install
white polyethylene wear plates and steel hopper plates
instead of black rubber curtains? [ ^ BACK
TO QUESTIONS ]
A: MBA
will install black rubber curtains if the customer insists,
however most customers prefer the benefits of the white
polyethylene wear plates. Black is the most common and
least expensive color for rubber; that is why it is
used. However, black rubber absorbs important cabinet
light. In addition, the thin, flexible rubber curtains
on the cabinet walls and doors are susceptible to the
air and abrasive from the blast nozzle. Most rubber
curtains are held in place with bolts and fender washers.
The air causes the curtains to flex and the abrasive
causes stress around the fender washers. It is not unusual
for the curtains to tear away from the anchors and begin
flapping inside the cabinet. MBA uses 3/16” white
polyethylene wear plates. The white polyethylene is
resistant to wear and does not absorb light. The plates
are rigid so it cannot tear free from the anchors and
flap.
Abrasive can get behind the rubber liners causing lifting
or ballooning. For this reason, MBA offers steel hopper
wear plates for extended wear. Steel hopper wear plates
are rigid, resulting in no lifting or ballooning.
Most cabinet
wear is in the machine hopper. The machine hopper gives
the abrasive two directions of flow rather than the
single direction of a machine sidewall. Most manufacturers
build their hoppers by bending the metal to create the
hopper sides. This causes metal fatigue and will eventually
create holes in the corners from abrasive wear. MBA
welds all sides of the hopper to reinforce the critical
abrasive wear points and eliminate potential wear problems.
--
Q: Why does MBA
use a fixed mount foot treadle instead of fixed foot
pedal or a moveable shrouded foot pedal?
[ ^ BACK TO QUESTIONS ]
A: The
ergonomic feature of a fixed foot treadle is important.
The operator can easily blast with either foot, thereby
offering the operator the ability to shift his weight
from one leg to the other leg. MBA offers an optional
shrouded foot pedal assembly for clients who prefer
it to a foot treadle.
--
Q: Why does
MBA use bar grate as the work surface in the standard
pressure blast cabinet instead of expanded metal or
perforated metal? [ ^ BACK TO QUESTIONS
]
A: The
bar grate prevents hopper wear created by the velocity
and density of the abrasive in the pressure blast cabinet.
The abrasive density and velocity in a pressure blast
cabinet is typically greater than a siphon blast cabinet.
The abrasive creates more frictional heat. Pressure
blast cabinets can also easily convey the heaviest of
abrasives; steel grit and steel shot. The reasons for
choosing a pressure blast cabinet instead of a siphon
blast cabinet are the very same reasons that the wear
on certain parts is higher in a pressure cabinet than
a siphon cabinet.
Using the proper bar spacing and
running the bars from side to side prevents the majority
of abrasive from blasting through the grates and hitting
the machine hopper. This helps extend the machine service
factor.
Many manufacturers use expanded
metal in their pressure blast cabinet. As the abrasive
travels past the part being processed, it passes through
the expanded metal work grate and hits the hopper. This
hopper wear is eliminated with the bar grate work surface.
Due to the vertical height of the bar grate, most of
the abrasive is unable to pass through the grate when
blasted at an angle of less than 45º (look at the
bar grate through the view window; you will be unable
to see through the bar grate).
--
Q: Why does MBA
offer so many machine models? [ ^ BACK
TO QUESTIONS ]
A:
Media Blast is a manufacturer of abrasive blasting cabinets.
In reality MBA is in the business of re-circulating
abrasive grains using compressed air. Different grain
sizes require different machine models. Abrasives that
are moisture prone because of their fine mesh size require
a cyclone separator reclaimer for proper feed and flow.
Heavy abrasives require a different type of separator
reclaimer.
MBA has created
different models so the customer doesn’t need
to know which options to add or subtract for proper
operation. If you require a process without frictional
heat, select the Hurricane Wet machine to solve your
problem.
In addition
to further simplify selection, MBA has created machine
models that are described and grouped using terms such
as: Light Duty, R&D and Production. This also helps
simplify machine selection when looking for the correct
machine type by listing the amount of usage per day
for machine operation.
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