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Dust Extraction System Design for Blast Rooms

In this blog, we will outline the top considerations for blast room ventilation through a dust extraction system.

How is ventilation used in a blast room

The ventilation requirements for an abrasive blast room depends on various factors, including the type and size of the blasting operation, the type of abrasive used, and the characteristics of the contaminants generated during the process. Adequate ventilation is essential to control airborne dust and other potentially hazardous particles and has a direct affect on the productivity of the operation and the safety of the operator.

The abrasive blast room pulse jet dust extraction system at Jewers Doors'

Ventilation and airspeed

There isn’t a one-size-fits-all answer to the question of the speed of air ventilation, as it can vary based on the specific circumstances of the blasting operation. However, industry standards and guidelines often provide recommendations for ventilation rates. As a rule of thumb 0.3mt/sec ventilation velocity will form the basis of a well-ventilated blast booth.

It’s recommended to consult relevant Blast Booth designers or a ventilation engineer to assess the specific conditions of your abrasive blast room. They can take into account factors such as the type of abrasive material, the size of the room, the blasting pressure, and the duration of the blasting operations to determine the appropriate ventilation requirements.

The importance of dust extraction system design

Keep in mind that effective ventilation is not just about the speed of air in the booth but also about proper design, capture and containment of contaminants, and replacement air introduction to the booth to ensure a safe and productive working environment. It is important to utilise a fan capable of overcoming both static and dynamic resistance built up in the system. Ducting and the filters themselves will provide a static load on the ventilation system. As debris builds up on filter material over its life this will too add further resistance. It is paramount that the fan can overcome these loads.

Airblast filter cartridge dust extraction system
3D render of a centrifugal fan.

Centrifugal fans

Centrifugal fans pull air perpendicular to the fan blades, creating a swirling or centrifugal motion. The air is then forced out radially from the fan housing. This provides a more directed and concentrated airflow. This makes centrifugal fans well-suited for applications where there are changes in the system’s resistance (e.g., ducts with bends and filters).

A centrifugal fan also generates higher static pressure compared to axial fans. This makes them suitable for overcoming the resistance caused by filters and ductwork in dust extraction systems.

Air inlets and outlets

When considering air inlets and outlets from the booth, air inlets should be designed to be large enough that air is not drawn into the booth at a speed capable of causing turbulence. A designer should not be tempted to restrict the air inlet aperture to avoid the risk of abrasive escape. Doing so only builds more static resistance into the system for the fan to overcome. The more static resistance is designed into the system, the less pressure is available to overcome the resistance generated as the filters slowly become blinded by dust. In short – restricting the air inlets results in a shorter filter life or reduced ventilation rates.

Back of the blast room air inlet and its ducting run up and back from one side of the compressor room to the extraction unit behind facility.
Dust extraction unit of the Wykes Commerical Vehicles blasting room, ducting at the top of the unit connects to the air inlets of the enclosure.

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Air outlets also have a critical contribution towards a well-ventilated blast room. Remember gravity is your friend. Whilst it might make the designers life easier to extract air from a blast booth at high level, thus avoiding the risk of good abrasive being drawn out of the booth unintentionally, this doesn’t make for an efficient system. Air out let’s should be located at low level and should be designed/sized such that they are a transitory section ventilating faster than the booth but slower than the duct. Air traveling through the air outlets should be slow enough to not be capable of suspending good abrasive, which should fall out of the airstream at this point and return to the blast booth. Duct speed should be sufficient to suspend dust all the way to the dust collector.

Once all of the above are correctly designed implemented a blast room should become a safe and productive environment.

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