Shot Peener and Blasting Operations

The abrasive generated dusts have some unique properties that need to be addressed to accomplish the following by application of advanced technology dust collector designs:

1)    Lowering the dust penetration through the filter cake filtering mechanism will protect the environment and employees.

2)    Re-circulation of the vented air can reduce energy consumption.

3)    Further economic savings, by lowering energy consumption, for operating the vent system at lower pressure drops and reducing pulsing air consumption.

4)    Filter life can be increased by 3 to 4 times.

 

For many years, abrasive blast operations were vented from the blast cabinets through mechanical shaker dust collectors. In these units the initial collection efficiency was relatively low. As the cake became thicker, the pressure drop increased. It would eventually increase so high that the flow through the system would be choked. 

Several mechanical arrangements to remove excess dust were development. During the process of removing the dust, a portion of the dust remained on the media. This residual dust had formed a filter cake and even after cleaning the collection efficiency was high enough to allow re-circulation. In the early 1960’s continuous cleaning pulse jet collectors were introduced. These collectors were much smaller than the mechanical cleaning collectors and reduced the complexity of the venting duct-work. The typical collector was 15-25% of the size of the compartment-ed mechanical cleaning collector. However, the average particulate load penetrating through the collector was about 2.5 milligrams per cubic meter, which could not be re-circulated into the working environment.

In 1973, pleated filter elements were introduced into the dust collection market. It was believed that pulse jet collectors would be more efficient if they were pleated because of low velocities through the filter element. Most dust collector manufacturers and designers packed too many pleats in the cartridge filter element. Also, the cleaning system was undersized for the amount of media at that must be cleaned.  The result is dust bridging on the inner pleat.  In many cases, we can lose up to 80% of the effective workable area of filter media.  This led to short filter life and high maintenance cost.

Advanced technology modifications have improved the operations of each of these types of collectors, reducing the foot print, lowering pressure drop (with lower power consumption) and reducing penetration of dust through the collectors. The next breakthrough in the advanced technology reverse pulse jet designs came in the realization that the capacity of a filter element depended on the reverse air volume of the cleaning jet. More volume could be applied per filter element and the footprint reduced drastically.

 

Cleaning System Designs must be sufficiently sized to develop the required volume to vent the process. The most volume that can be filtered depends on the number and size (or equivalent size) and number of valves. The advanced technology uses a proprietary supersonic nozzle design which increases the reverse jet flow by 70 per cent over a conventional orifice by getting a more efficient pressure to velocity conversion.

There are several considerations for safety and reliability that must be taken into account.

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