Dust Collection Challenges for Surface Preparation and Abrasive Blasting
Abrasive blasting and surface preparation are typically conducted within an enclosed room or chamber, which help to contain the dust created by the process. There are a number of challenges when it comes to collection of abrasive blasting dust.
- Reclamation of usable abrasive materials: Abrasive blasting requires a large volume of abrasive materials. Over time, these materials will break down into dust too fine to be effective for abrasive cleaning and blasting. However, a large amount of the material used in each round of abrasive blasting is still usable. It is preferable to collect these coarser materials for reuse. This will reduce costs and improve the sustainability of surface cleaning processes.
- Abrasive dust collection: Highly abrasive dusts like those used for surface preparation are tough on filters, ductwork and dust collector components. Large abrasive particles will wear through filter media rapidly or cause pinhole tears, which allow particulate to make it past the filter.
- Nuisance dust: Fine airborne dust inside the blasting area can reduce visibility, making it difficult for workers conducting blasting with hand-held tools. Uncontrolled dust of any type is also a housekeeping consideration.
- Combustible dusts: Many of the dusts created by abrasive blasting are combustible. That means they can generate an explosion when allowed to concentrate in the air or inside a dust collection machine. Special care must be taken when collecting combustible dusts to minimize the risks of an explosion inside the dust collector.
- Fire risk: Sparks can be created during abrasive blasting, especially when using metallic/slag abrasives on metallic surfaces. In addition, oil from the surfaces being cleaned can end up in the filters. This combination of sparks and oils creates an elevated risk of dust collector fires for surface preparation.
Health risks: Particulates created by abrasive blasting tend to be large and coarse, so they are not pulled as deeply into the lungs as fumed particulate from welding or other thermal processes. However, that does not mean that abrasive blasting dust is benign. Even non-toxic dust from materials such as corn cobs or walnut shells can cause severe lung irritation. Some materials are associated with specific health risks, including silicosis, lung cancer and other kinds of lung damage. Some slags used for abrasive blasting may contain trace amounts of arsenic, beryllium, cadmium or other toxic metals. Hazards can also arise from residues and old coatings on the surfaces being prepared, such as lead exposure when stripping older paints.
Dust Control Solutions for Surface Preparation and Abrasive Blasting
RoboVent offers robust dust collection solutions for surface preparation and abrasive blasting. We understand the challenges of working with highly abrasive materials.
There are several important considerations when designing a dust collection solution for abrasive materials. Specialized solutions are needed to extend the life of the filter and ductwork and reduce the risks of fire and combustion.
- Engineering controls and ventilation: As much as possible, abrasive blasting processes should be contained from the rest of the facility. If they are not already contained within a cabinet or enclosed blasting room, curtains or hoods can be used to contain blasting dust. Airflow should be designed to reduce the propagation of abrasive blasting dusts throughout the facility.
- Reusable material collection: The dust collection system should be designed with a method for collecting reusable material. For most abrasive blasting applications, a dropout box is the most efficient method. The dropout box is an open area designed to slow the velocity of air and allow larger, heavier particles to fall out of the airstream. Finer dust is pulled into the dust collector, where it is captured by the filter. The larger material can be collected for reuse.
- Dust collector design: Collection of abrasive dusts requires a rugged, heavy-duty dust collector. It should be equipped with an abrasion-resistant inlet valve. For heavy-duty applications, you can also consider having the interior of the dust collector lined with ceramic or an ultra-high molecular weight (UHMW) plastic. Careful consideration must also be given to factors such as air-to-cloth ratio and interstitial velocity (velocity of air inside the dust collector chamber). The system must be calibrated for the specific process; wheel blasting will have different requirements than air blasting.
- Ductwork design: Ductwork must be made of heavy-duty materials or have special linings so it will stand up to repeated abrasion by blasting dust. A longer run will reduce the risk of fire by giving sparks time to cool before they hit the filter. If the process generates a large number of sparks and ductwork cannot be designed with a long enough run, a spark suppression system may be considered.
- Fire suppression: The dust collector should be equipped with an internal fire suppression system for added protection against fires.
- Explosion mitigation: If you are collecting combustible dusts, you will need a deflagration system to reduce the chances of an explosion inside the dust collector and mitigate damage to the facility if an explosion should occur. These systems may include an explosion vent to release built-up pressure in the collector, an isolation valve to prevent pressure waves from propagating back into the facility, and a rotary airlock to keep collected dust safely contained in the hopper.
- Filters: The filter media must be durable with withstand abrasive dusts. Make sure the system has an effective pulsing system to pulse off excess dust and prevent premature filter loading. Because of the high risk of tears and abrasion, it is also important to make sure the system has a particulate monitoring system that can detect leaks past the filter.