Frequently Asked Questions
MBA Blast Cabinet Technology FAQs:
Q: Why are most MBA blast cabinets built standard with only one door? Back to Top
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 Top
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 Top
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 Top
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 Top
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 Top
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 Top
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 Top
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 Top
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 Top
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 Top
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 Top
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 Top
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.